Cascading effects of the loss of apex predatory sharks from a coastal ocean

Marine protected areas for demersal elasmobranchs in highly exploited Mediterranean ecosystems

Marine ecosystems are complex socio-ecological systems where sustainable solutions can be best gained by satisfying both conservation and socioeconomic demands. Concretely, the Mediterranean Sea is facing a huge demand of resources and marine activities while hosting abundant and unique biodiversity. It is considered an important elasmobranch hotspot where seventy-two elasmobranch species are present in the basin. Despite the recognised importance of elasmobranchs as umbrella species, to date only a small number of marine protected areas have been designated towards their protection. The paucity of spatially-explicit abundance data on elasmobranchs often precludes the designation of these areas to protect these marine predators. Here, we aimed to identify marine areas to protect elasmobranch species by means of a systematic spatial planning approach. We first estimated the spatial distribution of five elasmobranch species (three sharks and two rays) in the western Mediterranean Sea and then applied Marxan decision support tools to find priority marine conservation areas. We found that the five elasmobranchs are distributed in coastal and slope areas of the southern waters of the study area while in the northern region they are abundant in the continental slope and towards offshore waters. Conservation priority areas were identified in the southern part of the western Mediterranean. Adding more complex cost layers and zoning to the analysis did not alter conservation priority areas, confirming such areas are highly consistent and highly important for elasmobranch protection. The marine conservation priority areas identified here can contribute to designate a proactive area-based protection strategy towards elasmobranch conservation, related species and the habitats that they depend in the western Mediterranean Sea.

Ontogenetic trophic segregation between two threatened smooth-hound sharks in the Central Mediterranean Sea

Elasmobranchs are among the species most threatened by overfishing and a large body of evidence reports their decline around the world. As they are large predators occupying the highest levels of marine food webs, their removal can alter the trophic web dynamic through predatory release effects and trophic cascade. Suitable management of threatened shark species requires a good understanding of their behaviour and feeding ecology. In this study we provide one of the first assessments of the trophic ecology of the "vulnerable" smooth-hounds Mustelus mustelus and M. punctulatus in the Central Mediterranean Sea, based on stomach contents and stable isotope analyses. Ontogenetic diet changes were addressed by comparing the feeding habits of three groups of individuals: juveniles, maturing and adults. Our results highlighted that the two species share a similar diet based mostly on the consumption of benthic crustaceans (e.g. hermit crabs). Their trophic level increases during ontogeny, with adults increasing their consumption of large-sized crustaceans (e.g. Calappa granulata, Palinurus elephas), cephalopods (e.g. Octopus vulgaris) and fish (e.g. Trachurus trachurus). Our results provide also evidence of ontogenetic shifts in diet for both species showing a progressive reduction of interspecific trophic overlap during growth. The results of this study contribute to improve the current knowledge on the trophic ecology of these two threatened sharks in the Strait of Sicily, thus providing a better understanding of their role in the food web.

Latitude and protection affect decadal trends in reef trophic structure over a continental scale

The relative roles of top-down (consumer-driven) and bottom-up (resource-driven) forcing in exploited marine ecosystems have been much debated. Examples from a variety of marine systems of exploitation-induced, top-down trophic forcing have led to a general view that human-induced predator perturbations can disrupt entire marine food webs, yet other studies that have found no such evidence provide a counterpoint. Though evidence continues to emerge, an unresolved debate exists regarding both the relative roles of top-down versus bottom-up forcing and the capacity of human exploitation to instigate top-down, community-level effects. Using time-series data for 104 reef communities spanning tropical to temperate Australia from 1992 to 2013, we aimed to quantify relationships among long-term trophic group population density trends, latitude, and exploitation status over a continental-scale biogeographic range. Specifically, we amalgamated two long-term monitoring databases of marine community dynamics to test for significant positive or negative trends in density of each of three key trophic levels (predators, herbivores, and algae) across the entire time series at each of the 104 locations. We found that trophic control tended toward bottom-up driven in tropical systems and top-down driven in temperate systems. Further, alternating long-term population trends across multiple trophic levels (a method of identifying trophic cascades), presumably due to top-down trophic forcing, occurred in roughly fifteen percent of locations where the prerequisite significant predator trends occurred. Such alternating trophic trends were significantly more likely to occur at locations with increasing predator densities over time. Within these locations, we found a marked latitudinal gradient in the prevalence of long-term, alternating trophic group trends, from rare in the tropics (<5% of cases) to relatively common in temperate areas (~45%). Lastly, the strongest trends in predator and algal density occurred in older no-take marine reserves; however, exploitation status did not affect the likelihood of alternating long-term trophic group trends occurring. Our data suggest that the type and degree of trophic forcing in this system are likely related to one or more covariates of latitude, and that ecosystem resiliency to top-down control does not universally vary in this system based on exploitation level.

Ocean warming and hypoxia affect embryonic growth, fitness and survival of small-spotted catsharks, Scyliorhinus canicula

Elasmobranchs are key to a healthy marine ecosystem but are under threat from human activities, such as destructive fisheries and shark finning. Embryos of oviparous elasmobranchs may be further challenged during development by rising temperatures and falling dissolved oxygen concentrations in their intertidal environment. However, the impact of climate change on survival and growth of oviparous elasmobranchs is still poorly understood. Here, we investigate the effects of temperature and hypoxia on the growth and survival of small-spotted catshark (Scyliorhinus canicula) embryos by incubating eggs in normoxia 15°C, normoxia 20°C, hypoxia 15°C, or hypoxia 20°C. Incubation under the elevated temperature increased the embryonic growth rate, yolk consumption rate and Fulton's condition factor at hatching, whilst decreasing the total length and body mass of newly hatched sharks. Under low oxygen conditions (50% air saturation) the survival rate of S. canicula embryos dropped significantly and the temperature-induced increase in Fulton's condition factor was reversed. Together, these data demonstrate both the individual and compound effects of elevated temperature and hypoxia on the survival and growth during early ontogeny of a ubiquitous, coastal elasmobranch, S. canicula.

Inaccurate and Biased Global Media Coverage Underlies Public Misunderstanding of Shark Conservation Threats and Solutions

Sharks are a taxon of significant conservation concern and associated public interest. The scientific community largely supports management policies focusing on sustainable fisheries exploitation of sharks, but many concerned members of the public and some environmental advocates believe that sustainable shark fisheries cannot and do not exist and therefore support total bans on all shark fisheries and/or trade in shark products. The belief that sustainable shark fisheries cannot and do not exist persists despite scientific evidence showing that they can and do, and are important to livelihoods. Additionally, many concerned members of the public are only aware of one threat to sharks and are unaware of other threats—or of most available policy solutions. Here we assess whether the popular press plays a role in spreading misinformation and misunderstanding about these issues via the agenda-setting, priming, and cultivation roles of the media, with the goal of better understanding the causes and consequences of public confusion.

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The popular press plays a role in public understanding of environmental issues

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Many members of the public are misinformed about shark conservation

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We analyzed popular press coverage of shark conservation topics

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Topics were frequently covered in a biased, misleading, or incorrect way

Functional diversity of marine megafauna in the Anthropocene

Marine megafauna, the largest animals in the oceans, serve key roles in ecosystem functioning. Yet, one-third of these animals are at risk of extinction. To better understand the potential consequences of megafaunal loss, here we quantify their current functional diversity, predict future changes under different extinction scenarios, and introduce a new metric [functionally unique, specialized and endangered (FUSE)] that identifies threatened species of particular importance for functional diversity. Simulated extinction scenarios forecast marked declines in functional richness if current trajectories are maintained during the next century (11% globally; up to 24% regionally), with more marked reductions (48% globally; up to 70% at the poles) beyond random expectations if all threatened species eventually go extinct. Among the megafaunal groups, sharks will incur a disproportionate loss of functional richness. We identify top FUSE species and suggest a renewed focus on these species to preserve the ecosystem functions provided by marine megafauna.

How Sharks and Shark–Human Interactions are Reported in Major Australian Newspapers

Few phrases evoke more negative emotion, or generate more media coverage, than ‘shark attack’ despite the few deaths that have been attributed to shark bite. Typically, tabloids are considered to provide more sensational coverage than broadsheets. We investigated how sharks and shark–human interactions were portrayed in four major Australian newspapers during a period of a record number of shark attacks in Australian waters. There was strong focus on human risk from sharks, and over-reportage of negative aspects. Thirty incidents were recorded: two fatal, 20 injury, and eight ‘near-miss’. Of 309 ‘shark’ articles surveyed, 24% mentioned fatalities (65% occurred prior to the study, some decades earlier). Injury was reported in 40% of articles, and ‘near-miss’ in 33% (89% related to an incident in South Africa involving an Australian surfing celebrity). The tabloid, Telegraph, published substantially more shark-related articles and photographs than other newspapers. There was otherwise no consistent pattern of difference between genre or newspapers.

Enemies with benefits: integrating positive and negative interactions among terrestrial carnivores

Interactions among terrestrial carnivores involve a complex interplay of competition, predation and facilitation via carrion provisioning, and these negative and positive pathways may be closely linked. Here, we developed an integrative framework and synthesized data from 256 studies of intraguild predation, scavenging, kleptoparisitism and resource availability to examine global patterns of suppression and facilitation. Large carnivores were responsible for one third of mesocarnivore mortality (n = 1,581 individuals), and intraguild mortality rates were superadditive, increasing from 10.6% to 25.5% in systems with two vs. three large carnivores. Scavenged ungulates comprised 30% of mesocarnivore diets, with larger mesocarnivores relying most heavily on carrion. Large carnivores provided 1,351 kg of carrion per individual per year to scavengers, and this subsidy decreased at higher latitudes. However, reliance on carrion by mesocarnivores remained high, and abundance correlations among sympatric carnivores were more negative in these stressful, high-latitude systems. Carrion provisioning by large carnivores may therefore enhance suppression rather than benefiting mesocarnivores. These findings highlight the synergistic effects of scavenging and predation risk in structuring carnivore communities, suggesting that the ecosystem service of mesocarnivore suppression provided by large carnivores is strong and not easily replaced by humans.

Variation in cownose ray Rhinoptera neglecta abundance and group size on the central east coast of Australia

Here, we provide baseline information about the relative abundance and group size of the Australian cownose ray Rhinoptera neglecta on the central east coast of Australia. Using drone monitoring over 2 years, we completed 293 transects, each 2 km in length, at four locations distributed along c.100 km of coast. In total, 5979 R. neglecta were observed with overall relative abundance (±SE) of, 20.4 (±3.3) individuals per transect. The numbers of R. neglecta varied among locations, with the highest density found off the beach adjacent to the river mouth at Evans Head. The number of rays observed also decreased with increasing wind speed. While some of this relationship was probably associated with visibility, R. neglecta may also move offshore during strong winds. We found no evidence that R. neglecta was under significant threat. Additionally, our cost-effective surveys demonstrate the utility of aerial drones in fisheries conservation biology.

Anthropogenic pressures negatively impact genomic diversity of the vulnerable seagrass Zostera capensis

Zostera capensis is a keystone species providing essential ecosystem services to southern African coastal systems. Like most seagrasses globally, Z. capensis is declining and under threat from anthropogenic pressures, and indicators of seagrass health and resilience may be of interest in preventing further declines. As intraspecific diversity is an important component of resilience, we used a pooled RADseq approach to generate genome-wide measures of variation across the entire South African distribution of Z. capensis. Using nucleotide diversity, heterozygosity and allelic richness we tested for associations with fine-scale anthropogenic pressure data compiled by the South African National Biodiversity Assessment using generalised linear models. Increased fishing effort, habitat loss, sand mining and a change in estuary flow dynamics were found to play an important role in decreasing nucleotide diversity and expected heterozygosity, most likely due to the loss of less resilient genotypes as a result of direct physical damage or indirect consequences. As the building block for adaptation, nucleotide diversity is particularly important for resilience. Because of this, as well as the fact that nucleotide diversity displayed the most distinct difference between the west and east coast, and responded most strongly to anthropogenic pressures, we suggest that this may be a useful measure for monitoring genetic or genomic variation. As genomic diversity influences resilience and resistance to disturbances, the remaining diversity in South African seagrass beds urgently needs to be conserved through restoration efforts and careful management of pressures.

From sea monsters to charismatic megafauna: Changes in perception and use of large marine animals

Marine megafauna has always elicited contrasting feelings. In the past, large marine animals were often depicted as fantastic mythological creatures and dangerous monsters, while also arousing human curiosity. Marine megafauna has been a valuable resource to exploit, leading to the collapse of populations and local extinctions. In addition, some species have been perceived as competitors of fishers for marine resources and were often actively culled. Since the 1970s, there has been a change in the perception and use of megafauna. The growth of marine tourism, increasingly oriented towards the observation of wildlife, has driven a shift from extractive to non-extractive use, supporting the conservation of at least some species of marine megafauna. In this paper, we review and compare the changes in the perception and use of three megafaunal groups, cetaceans, elasmobranchs and groupers, with a special focus on European cultures. We highlight the main drivers and the timing of these changes, compare different taxonomic groups and species, and highlight the implications for management and conservation. One of the main drivers of the shift in perception, shared by all the three groups of megafauna, has been a general increase in curiosity towards wildlife, stimulated inter alia by documentaries (from the early 1970s onwards), and also promoted by easy access to scuba diving. At the same time, environmental campaigns have been developed to raise public awareness regarding marine wildlife, especially cetaceans, a process greatly facilitated by the rise of Internet and the World Wide Web. Currently, all the three groups (cetaceans, elasmobranchs and groupers) may represent valuable resources for ecotourism. Strikingly, the economic value of live specimens may exceed their value for human consumption. A further change in perception involving all the three groups is related to a growing understanding and appreciation of their key ecological role. The shift from extractive to non-extractive use has the potential for promoting species conservation and local economic growth. However, the change in use may not benefit the original stakeholders (e.g. fishers or whalers) and there may therefore be a case for providing compensation for disadvantaged stakeholders. Moreover, it is increasingly clear that even non-extractive use may have a negative impact on marine megafauna, therefore regulations are needed.

Long-term patterns of abundance, residency and movements of bull sharks (Carcharhinus leucas) in Sydney Harbour, Australia

Bull sharks (Carcharhinus leucas) are known to frequent nearshore environments, particularly estuaries, resulting in interactions with humans. Knowledge of the behaviour of large individuals in temperate, estuarine environments is limited. This acoustic telemetry study reports on residency and movement patterns of 40 sub-adult and adult bull sharks in Sydney Harbour, a large temperate estuary, over seven years. Bull sharks exhibited clear seasonal patterns in their occurrence during the austral summer and autumn, with abundance peaking in January and February. This pattern was consistent between sexes and across all sizes. Bull sharks displayed weak diel differences in their spatial distribution, with individuals using areas further from the Harbour entrance more frequently during the day and at low tides. A diel pattern in depth use was apparent, with sharks utilising deeper water during daytime and moving shallower at night. Bull sharks had high individual inter-annual variability in their spatial distribution, however, when data were aggregated among all individuals and years, two locations of increased use were identified. Water temperature was the key predictor for seasonal movements and return behaviour to this estuary, suggesting that increasing water temperatures as a result of climate change may lead to higher shark abundance and possibly longer periods of residency in Sydney Harbour. Understanding the drivers for bull shark abundance and distribution will hopefully facilitate better education and shark smart behaviour by estuarine water-users, especially during summer and autumn months.

Contrasting global, regional and local patterns of genetic structure in gray reef shark populations from the Indo-Pacific region

Human activities have resulted in the loss of over 90% of sharks in most ocean basins and one in four species of elasmobranch are now listed at risk of extinction by the IUCN. How this collapse will affect the ability of populations to recover in the face of continued exploitation and global climate change remains unknown. Indeed, important ecological and biological information are lacking for most shark species, particularly estimates of genetic diversity and population structure over a range of spatial scales. Using 15 microsatellite markers, we investigated genetic diversity and population structure in gray reef sharks over their Indo-Pacific range (407 specimens from 9 localities). Clear genetic differentiation was observed between the Indian and the Pacific Ocean specimens (F_ST = 0.145***). Further differentiation within the Pacific included a West and East cleavage as well as North-Central and South-Central Pacific clusters. No genetic differentiation was detected within archipelagos. These results highlight the legacy of past climate changes and the effects of large ocean expanses and circulation patterns on contrasting levels of connectivity at global, regional and local scales. Our results indicate a need for regional conservation units for gray reef sharks and pinpoint the isolation and vulnerability of their French Polynesian population.

Reproductive biology, multiple paternity and polyandry of the bull shark Carcharhinus leucas

To improve understanding of bull shark Carcharhinus leucas reproductive biology, we analysed reproductive traits from 118 bull sharks caught along Reunion Island coasts (Western Indian Ocean), including 16 gravid females. Specific microsatellite loci were used to investigate the frequency of multiple paternity. Males and females reached maturity at c. 234 cm and 257 cm total length (L_T ), respectively, and litter sizes ranged from 5 to 14 embryos. Analysis of the 16 litters collected in various months of the year indicated that parturition occurs between October and December, with a size at birth c. 60-80 cm L_T and that the gestation period is probably c. 12 months. Assuming a 1 year resting period and a period of sperm storage (4-5 months) between mating (in June-September) and fertilisation, the reproductive cycle of bull sharks at Reunion Island would be biennial. At least 56.25% of the litters investigated were polyandrous, sired by 2-5 males. Several males that each sired several litters conceived during the same or distinct mating seasons were detected, suggesting both a seasonal aggregation of sharks to mate and some male fidelity to mating site. Altogether, these findings provide valuable information for both shark risk management and conservation of the species in the Western Indian Ocean.

A matter of taste: Spatial and ontogenetic variations on the trophic ecology of the tiger shark at the Galapagos Marine Reserve

Sharks are top predators across ocean food webs and have a major ecological role in marine ecosystems. Investigating the trophic ecology of this group of species is thus essential to understand ecosystem functioning and inform specific management actions aimed at shark conservation. The Galapagos Islands represent one of the last ocean wildernesses, where populations of sharks and other top marine predators come close to a pristine status. Here we provide the first study on the trophic ecology of the tiger shark (Galeocerdo cuvier) within the Galapagos Marine Reserve (GMR), using a combination of stable isotope analysis, satellite tracking, and passive acoustic telemetry to investigate ontogenetic and spatial variations at two regions. The mean estimated δ¹³C and δ¹⁵N at Isabela island (western region) were -13.9 ± 0.5‰ and 13.7 ± 0.7‰; and for Santa Cruz island (central region) were -13.8 ± 0.3‰ and 13.4 ± 0.7‰, respectively. Green sea turtles (Chelonia mydas) were the main prey item for large tiger sharks (>280 cm TL), while smaller sharks mainly fed on squid and pelagic fish. Tiger sharks exhibited a high degree of philopatry around green sea-turtle nesting areas, with the majority of sharks detected around green sea-turtle nesting areas for at least 10 months after their capture date, and some individuals were even present during the entire three-year study period. Although we did not report statistically significant differences between the two regions, isotopic and electronic tagging data suggest that tiger sharks in the Galapagos could be segregated into specific populations separated by geographical scales of <100 km. The high productivity of the archipelago, along with the protection from industrial fishing granted by the GMR, result in abundant and predictable sources of prey. This high food abundance, combined with the presence of suitable habitats throughout the tiger shark life cycle, might result in a reduction of migratory behaviours when compared to movement patterns of tiger sharks in other ocean basins. Additional studies using genetic tools could provide further evidence on the presence of separate management units, as it has been recently revealed for other shark species inhabiting the GMR.

Similar bacterial communities on healthy and injured skin of black tip reef sharks

Background

Sharks are in severe global decline due to human exploitation. The additional concern of emerging diseases for this ancient group of fish, however, remains poorly understood. While wild-caught and captive sharks may be susceptible to bacterial and transmissible diseases, recent reports suggest that shark skin may harbor properties that prevent infection, such as a specialized ultrastructure or innate immune properties, possibly related to associated microbial assemblages. To assess whether bacterial community composition differs between visibly healthy and insulted (injured) shark skin, we compared bacterial assemblages of skin covering the gills and the back from 44 wild-caught black-tip reef sharks (Carcharhinus melanopterus) from the Amirante Islands (Seychelles) via 16S rRNA gene amplicon sequencing.

Results

Shark skin-associated bacterial communities were diverse (5971 bacterial taxa from 375 families) and dominated by three families of the phylum Proteobacteria typical of marine organisms and environments (Rhodobacteraceae, Alteromonadaceae, Halomonadaceae). Significant differences in bacterial community composition of skin were observed for sharks collected from different sites, but not between healthy or injured skin samples or skin type (gills vs. back). The core microbiome (defined as bacterial taxa present in ≥50% of all samples) consisted of 12 bacterial taxa, which are commonly observed in marine organisms, some of which may be associated with animal host health.

Conclusion

The conserved bacterial community composition of healthy and injured shark skin samples suggests absence of severe bacterial infections or substantial pathogen propagation upon skin insult. While a mild bacterial infection may have gone undetected, the overall conserved bacterial community implies that bacterial function(s) may be maintained in injured skin. At present, the contribution of bacteria, besides intrinsic animal host factors, to counter skin infection and support rapid wound healing in sharks are unknown. This represents clear knowledge gaps that should be addressed in future work, e.g. by screening for antimicrobial properties of skin-associated bacterial isolates.

Electronic supplementary material

The online version of this article (10.1186/s42523-019-0011-5) contains supplementary material, which is available to authorized users.

Shark ecology, the role of the apex predator and current conservation status

Feeding studies, since traditional stomach content analysis to stable isotopes analyses, provides insights into the trophic relationship among the apex predators and the ecosystems they inhabit. The Pacific Coast of Mexico (PCM) is inhabited by 62 known species (or 12%) of living sharks, which belong to 21 families and 34 genera. We divide the Pacific Coast of Mexico (PCM) into four regions for consideration: (1) the western coast of Baja California (WcBJ), (2) the Gulf of California (GC), (3) the Central Pacific Mexican (CPM), and (4) the Gulf of Tehuantepec (GT). Biodiversity is highest in the GC, with 48 shark species, followed by the WcBJ with 44 species, then the CPM with 28 species and the GT with 26 species. Few large species (>2m in total length) function as top predators in any region, with a greater number of smaller shark species (<1.5m total length). Information about the trophic ecology of different shark species is included to know the ecological role and position of each shark species within a food web to understand the dynamics of marine communities and the impact that each species has on trophic net, which is critical to effective resource conservation and responsible exploitation. The different shark species predate mainly on coastal or oceanic waters. The coastal sharks feed mainly on crustaceans and small fishes; whereas the oceanic species predate mainly on squids and fishes from mesopelagic to epipelagic habits. Also is included a summary of the IUCN Red List category assigned to all shark species from the Mexican Pacific. Thirty-one percent (19 species) of sharks in the Mexican Pacific are considered as threatened (Critically Endangered, Endangered or Vulnerable). Of these, 4.9% (3 species) are Endangered and 26.2% (15 species) are Vulnerable. In addition, since 2012 the fishing of shark and rays has been closed between 1 May and 31 July in the Mexican Pacific as a conservative management measure.

Patterns of predation on native and invasive alien fish in Mediterranean protected and unprotected areas

Worldwide, the loss of predatory fish due to overexploitation has altered the structure of native communities and caused ecosystem shifts. Ecosystems deprived of high-level predators may be more vulnerable to invasive alien species as the latter are subject to reduced predation control. Marine protected areas (MPAs), and particularly no-take reserves where fishing is banned, can be effective tools for the restoration of predatory relationships within their boundaries. We explored whether the restoration of high-level predatory fish populations within Mediterranean MPAs can exert top-down control on alien fish. Fish tethering experiments, including native (Sardina pilchardus, Boops boops) and alien (Siganus rivulatus) dead specimens, were conducted to quantify predation within the no-take zones of three MPAs and in unprotected areas, and to assess potential differences in predation rates and prey type preferences. A subsample of experimental units was filmed to document predation events and related fish behaviour. More high-level predators interacted with the tethered fish inside the MPAs than in unprotected areas. Yet we did not find significant differences in the consumption of alien or native fishes between MPAs and unprotected areas. The native S. pilchardus was consumed more in comparison to the other tethered fishes, regardless of protection status and location. Interestingly, the alien S. rivulatus was consumed by native predators in the western Mediterranean locations where this alien fish is not established. Despite its limitations, our study provides evidence on the ability of some native predators to feed on and potentially control certain alien species without requiring 'adaptive' time-lag periods.

Protection from illegal fishing and shark recovery restructures mesopredatory fish communities on a coral reef

The recovery of communities of predatory fishes within a no-take marine reserve after the eradication of illegal fishing provides an opportunity to examine the role of sharks and other large-bodied mesopredatory fishes in structuring reef fish communities. We used baited remote underwater video stations to investigate whether an increase in sharks was associated with a change in structure of the mesopredatory fish community at Ashmore Reef, Western Australia. We found an almost fourfold increase in shark abundance in reef habitat from 0.64 hr-1 ± 0.15 SE in 2004, when Ashmore Reef was being fished illegally, to 2.45 hr-1 ± 0.37 in 2016, after eight years of full-time enforcement of the reserve. Shark recovery in reef habitat was accompanied by a two and a half-fold decline in the abundance of small mesopredatory fishes (≤50 cm TL) (14.00 hr-1 ± 3.79 to 5.6 hr-1 ± 1.20) and a concomitant increase in large mesopredatory fishes (≥100 cm TL) from 1.82 hr-1 ± 0.48 to 4.27 hr-1 ± 0.93. In contrast, near-reef habitats showed an increase in abundance of large mesopredatory fishes between years (2.00 hr-1 ± 0.65 to 4.56 hr-1 ± 1.11), although only smaller increases in sharks (0.67 hr-1 ± 0.25 to 1.22 hr-1 ± 0.34) and smaller mesopredatory fishes. Although the abundance of most mesopredatory groups increased with recovery from fishing, we suggest that the large decline of small mesopredatory fish in reef habitat was mostly due to higher predation pressure following the increase in sharks and large mesopredatory fishes. At the regional scale, the structure of fished communities at Ashmore Reef in 2004 resembled those of present day Scott Reefs, where fishing still continues today. In 2016, Ashmore fish communities resembled those of the Rowley Shoals, which have been protected from fishing for decades.

The pros and cons of the invasive freshwater apex predator, European catfish Silurus glanis, and powerful angling technique for its population control

Catfish have spread across Europe and several countries out of this region within the last decades. Basic knowledge of this apex predator has revealed concerns of invasive behaviour and questions regarding its utilization as a biomanipulation species. However, a method enabling its regulation to a required level has not yet been developed. We simulated the impact of angling on the catfish population by method of hook-lines in two post-mining lakes with a monitored population consisting of tagged individuals and in two reservoirs as reference sites. Further, the efficiency of hook-lines as a reducing device was examined and the economic aspects were determined. Catfish population in localities where the species is unwanted or invasive may be efficiently reduced to a harmless level by hook-lines and angling (depending on the approach of anglers). The most efficient time of the year seems to be spring to early summer with catch efficiency of 5.4 individuals per 10 baits in one day. The catch efficiency markedly decreased during the second part of the year and did not exceed 2.8 individuals per 10 baits in one day. Mean size of catfish had negative impact whereas catfish biomass had positive impact on the catch efficiency. Trophic status and number of catfish in the locality had no impact on the catch efficiency. According to model, 11-18 bait-days per 1 ha per season is efficient to decrease catfish population to 10% of the original size. Both angling and hook-lines are very simple, they are financially and time bearable mechanisms of catfish regulation in any condition. However, catfish play an important role as a biomanipulative species in many localities. In this case where catfish is beneficial, angling presents a real threat of population collapse and loss of the biomanipulative effect.

Top predators induce habitat shifts in prey within marine protected areas

Emerging conservation efforts for the world's large predators may, if successful, restore natural predator-prey interactions. Marine reserves, where large predators tend to be relatively common, offer an experimental manipulation to investigate interactions between large-bodied marine predators and their prey. We hypothesized that southern stingrays-large, long-lived and highly interactive mesopredators-would invest in anti-predator behavior in marine reserves where predatory large sharks, the primary predator of stingrays, are more abundant. Specifically, we predicted southern stingrays in marine reserves would reduce the use of deep forereef habitats in the favor of shallow flats where the risk of shark encounters is lower. Baited remote underwater video was used to survey stingrays and reef sharks in flats and forereef habitats of two reserves and two fished sites in Belize. The interaction between "protection status" and "habitat" was the most important factor determining stingray presence. As predicted, southern stingrays spent more time interacting with baited remote underwater videos in the safer flats habitats, were more likely to have predator-inflicted damage inside reserves, and were less abundant in marine reserves but only in the forereef habitat. These results are consistent with a predation-sensitive habitat shift rather than southern stingray populations being reduced by direct predation from reef sharks. Our study provides evidence that roving predators can induce pronounced habitat shifts in prey that rely on crypsis and refuging, rather than active escape, in high-visibility, heterogeneous marine habitats. Given documented impacts of stingrays on benthic communities it is possible restoration of reef shark populations with reserves could induce reef ecosystem changes through behavior-mediated trophic cascades.

Managing yield and resilience in a harvested tri-trophic food chain model

In this article, we compare the two ecological services known as yield and resilience, for a tri-trophic food chain model consisting of a prey, an intermediate predator and a top predator. For this comparison process, we use both analytical and numerical techniques. It is shown that a variety of patterns are possible based on the intensity of efforts distributed among different trophic levels. Thus we may suggest that fishing down the food chain, as suggested by Pauly et al. (1998) is not bound to happen. Our analysis also shows that balancing the harvest between prey, intermediate predator and top predator could give more yield and stabilizing the ecosystem, than the selective harvesting of any one species. This balanced harvesting may not be a win-win situation for yield and resilience, but it could be a most favourable strategy to balance them. This research would help to correlate resilience with yield and determines the desirable selection of two policies, resilience maximizing yield or maximum sustainable yield to safeguard ecological communities.

Genetic population structure and demography of an apex predator, the tiger shark Galeocerdo cuvier

Population genetics has been increasingly applied to study large sharks over the last decade. Whilst large shark species are often difficult to study with direct methods, improved knowledge is needed for both population management and conservation, especially for species vulnerable to anthropogenic and climatic impacts. The tiger shark, Galeocerdo cuvier, is an apex predator known to play important direct and indirect roles in tropical and subtropical marine ecosystems. While the global and Indo-West Pacific population genetic structure of this species has recently been investigated, questions remain over population structure and demographic history within the western Indian (WIO) and within the western Pacific Oceans (WPO). To address the knowledge gap in tiger shark regional population structures, the genetic diversity of 286 individuals sampled in seven localities was investigated using 27 microsatellite loci and three mitochondrial genes (CR,COI, and cytb). A weak genetic differentiation was observed between the WIO and the WPO, suggesting high genetic connectivity. This result agrees with previous studies and highlights the importance of the pelagic behavior of this species to ensure gene flow. Using approximate Bayesian computation to couple information from both nuclear and mitochondrial markers, evidence of a recent bottleneck in the Holocene (2,000-3,000 years ago) was found, which is the most probable cause for the low genetic diversity observed. A contemporary effective population size as low as 111 [43,369] was estimated during the bottleneck. Together, these results indicate low genetic diversity that may reflect a vulnerable population sensitive to regional pressures. Conservation measures are thus needed to protect a species that is classified as Near Threatened.

Trace metals and persistent organic pollutants contamination in batoids (Chondrichthyes: Batoidea): A systematic review

Batoids (Chondrichthyes: Batoidea; e.g. stingrays, skates, and guitarfish) comprise more than 55% of elasmobranch taxa and represent ecologically important predators in benthic and pelagic habitats. Although overexploitation and habitat degradation are the two biggest threats to batoid populations, coastal and oceanic pollution is also a pervasive potential threat. In this systematic review, we compile published scientific literature on trace metals and persistent organic pollutants (POPs) contamination in elasmobranch species of the Batoidea superorder and present contamination patterns, exposure effects, and potential human exposure risks to most reported contaminants. We found batoids to accumulate a wide range of trace metals, including mercury (Hg), arsenic (As), lead (Pb), copper (Cu), cadmium (Cd) and zinc (Zn). Accumulation of POPs is reported for chlordanes, dichlorodiphenyltrichloroethane (DDT), polychlorinated biphenyl (PCB), dieldrin, Heptachlor epoxide, hexachlorobenzene and perfluoroalkyl substances (PFAS). Hg levels in muscle tissue were significantly different among oceanic basins and habitats, consistent with previous global assessments of Hg oceanic background levels. Some batoid species presented Hg levels higher than large pelagic teleost fishes and comparable to sharks. Ecological traits such as, bottom feeding, upper trophic position and elasmobranch-specific physiology and metabolism are discussed as potential factors associated with Hg uptake and accumulation in batoids. Some species exceeded USEPA's maximum contamination safety limits in edible tissues for Hg, As and ΣPCBs. For most trace metals and POPs, there is a lack of studies focusing on contamination levels in batoids. We recommend future research increasing reporting on POPs and trace metals besides Hg in batoids to further investigate the role of Elasmobranch as a bioindicator for marine pollution.

Long-term dietary shift and population decline of a pelagic seabird-A health check on the tropical Atlantic?

In the face of accelerating ecological change to the world's oceans, seabirds are some of the best bio-indicators of marine ecosystem function. However, unravelling ecological changes that pre-date modern monitoring programmes remains challenging. Using stable isotope analysis of feathers and regurgitants collected from sooty terns (Onychoprion fuscatus) nesting at a major Atlantic colony, we reconstructed a long-term dietary time series from 1890 to the present day and show that a significant dietary shift occurred during the second half of the twentieth century coinciding with an apparent population collapse of approximately 84%. After correcting for the "Suess Effect," δ¹³ C in feathers declined by ~1.5‰ and δ¹⁵ N by ~2‰ between the 1890s and the present day, indicating that birds changed their diets markedly over the period of population decline. Isotopic niches were equally wide before and after the population collapse but isotopic mixing models suggest that birds have grown ever more reliant on nutrient-poor squid and invertebrates as teleost fish have declined in availability. Given that sooty terns rely heavily on associations with sub-surface predators such as tuna to catch fish prey, the rapid expansion of industrialized fisheries for these species over the same period seems a plausible mechanism. Our results suggest that changes to marine ecosystems over the past 60 years have had a dramatic impact on the ecology of the most abundant seabird of tropical oceans, and highlight the potentially pervasive consequences of large predatory fish depletion on marine ecosystem function.

Shifting headlines? Size trends of newsworthy fishes

The shifting baseline syndrome describes a gradual lowering of human cognitive baselines, as each generation accepts a lower standard of resource abundance or size as the new norm. There is strong empirical evidence of declining trends of abundance and body sizes of marine fish species reported from docks and markets. We asked whether these widespread trends in shrinking marine fish are detectable in popular English-language media, or whether news writers, like many marine stakeholders, are captive to shifting baselines. We collected 266 English-language news articles, printed between 1869 and 2015, which featured headlines that used a superlative adjective, such as 'giant', 'huge', or 'monster', to describe an individual fish caught. We combined the reported sizes of the captured fish with information on maximum species-specific recorded sizes to reconstruct trends of relative size (reported size divided by maximum size) of newsworthy fishes over time. We found some evidence of a shifting baseline syndrome in news media over the last 140 years: overall, the relative length of the largest fish worthy of a headline has declined over time. This pattern held for charismatic fish species (e.g. basking sharks, whale sharks, giant mantas), which are now reported in the media at smaller relative lengths than they were near the turn of the 20th century, and for the largest species under high risk of extinction. In contrast, there was no similar trend for pelagic gamefish and oceanic sharks, or for species under lower risk of extinction. While landing any individual of the large-bodied 'megafish' may be newsworthy in part because of their large size relative to other fish species, the 'megafish' covered in our dataset were small relative to their own species-on average only 56% of the species-specific maximum length. The continued use in the English-language media of superlatives to describe fish that are now a fraction of the maximum size they could reach, or a fraction of the size they used to be, does reflect a shifting baseline for some species. Given that media outlets are a powerful tool for shaping public perception and awareness of environmental issues, there is a real concern that such stories might be interpreted as meaning that superlatively large fish still abound.

Trophic declines and decadal-scale foraging segregation in three pelagic seabirds

We investigated how foraging habits vary among three ecologically distinct wide-ranging seabirds. Using amino acid δ¹⁵N proxies for nutrient regime (δ¹⁵N_Phe) and trophic position (Δδ¹⁵N_Glu-Phe), we compared Newell's shearwater (Puffinus newelli) and Laysan albatross (Phoebastria immutabilis) foraging habits over the past 50-100 years, respectively, to published records for the Hawaiian petrel (Pterodroma sandwichensis). Standard ellipses constructed from the isotope proxies show that inter-population and interspecific foraging segregation have persisted for several decades. We found no evidence of a shift in nutrient regime at the base of the food web for the three species. However, our data identify a trophic decline during the past century for Newell's shearwater and Laysan albatross (probability ≥ 0.97), echoing a similar decline observed in the Hawaiian petrel. During this time, Newell's shearwaters and Hawaiian petrels have experienced population declines and Laysan albatross has experienced range extension and apparent population stability. Counting other recent studies, a pattern of trophic decline over the past century has now been identified in eight species of pelagic seabirds that breed in the Hawaiian Islands. Because our study species forage broadly across the North Pacific Ocean and differ in morphological and behavioral traits and feeding methods, the identified trophic declines suggest a pervasive shift in food web architecture within the past century.

Reproductive Science in Sharks and Rays

Sharks and rays make up 96% of the class Chondrichthyes. They are among the most endangered of any taxa, threatened through habitat loss, overfishing and hunting for shark fin soup, traditional medicines or sport, and because many species are slow to mature and produce low numbers of offspring. Sharks and rays are ecologically and reproductively diverse, though basic knowledge of their reproductive physiology is lacking for many species. There has been a move towards non-lethal approaches of data collection in sharks and rays, especially with reproductive technologies such as ultrasound and hormone analysis. Additionally, technologies such as semen collection and artificial insemination are lending themselves to develop tools to manage small or closed populations, with cold-stored sperm being shipped between institutions to maximize genetic diversity in managed populations. The role of steroid hormones in elasmobranch reproduction appears broadly conserved, though heavily influenced by environmental cues, especially temperature. For this reason elasmobranchs are likely at risk of reproductive perturbations due to environmental changes such as ocean warming. Current reproductive technologies including computer assisted sperm assessments to study warming effects on sperm motility and intra-uterine satellite tags to determine birthing grounds will serve to generate data to mitigate anthropogenic changes that threaten the future of this vulnerable groups of fish.

Decline of coastal apex shark populations over the past half century

Overexploitation of large apex marine predators is widespread in the world's oceans, yet the timing and extent of declines are poorly understood. Here we reconstruct a unique fisheries-independent dataset from a shark control programme spanning 1760 km of the Australian coastline over the past 55 years. We report substantial declines (74-92%) of catch per unit effort of hammerhead (Sphyrnidae), whaler (Carcharhinidae), tiger shark (Galeocerdo cuvier) and white sharks (Carcharodon carcharias). Following onset of the program in the 1960s, catch rates in new installations in subsequent decades occurred at a substantially lower rate, indicating regional depletion of shark populations over the past half a century. Concurrent declines in body size and the probability of encountering mature individuals suggests that apex shark populations are more vulnerable to exploitation than previously thought. Ongoing declines and lack of recovery of vulnerable and protected shark species are a cause for concern.

A metabarcoding approach for the feeding habits of European hake in the Adriatic Sea

European hake (Merluccius merluccius) is one of the most economically important fish for the Mediterranean Sea. It is an important predator of deep upper shelf slope communities currently characterized by growth overexploitation: the understanding of hake's diet might support next generation management tools. However, all current European hake diet studies depend on the morphological identification of prey remains in stomach content, with consequent limitations. In this study, we set up a metabarcoding approach based on cytochrome oxidase I PCR amplification and Miseq Illumina paired-end sequencing of M. merluccius stomach content remains and compared the results to classic morphological analyses. A total of 95 stomach contents of M. merluccius sampled in the North-Central Adriatic Sea were analyzed with both the metabarcoding and morphological approaches. Metabarcoding clearly outperformed the morphological method in the taxonomic identification of prey describing more complex trophic relationships even when considering the morphological identification of 200 stomach contents. Statistical analysis of diet composition revealed a weak differentiation among the hake's size classes, confirming an opportunistic feeding behavior. All the analyses performed showed the presence of a core of shared prey among the size classes and a cloud of size-specific prey. Our study highlights the exceptional potential of metabarcoding as an approach to provide unprecedented taxonomic resolution in the diet of M. merluccius and potentially of other marine predators, due to the broad-spectrum of detection of the primers used. A thorough description of these complex trophic relationships is fundamental for the implementation of an ecosystem approach to fisheries.

Using tagging data and aerial surveys to incorporate availability bias in the abundance estimation of blue sharks (Prionace glauca)

There is worldwide concern about the status of elasmobranchs, primarily as a result of overfishing and bycatch with subsequent ecosystem effects following the removal of top predators. Whilst abundant and wide-ranging, blue sharks (Prionace glauca) are the most heavily exploited shark species having suffered marked declines over the past decades, and there is a call for robust abundance estimates. In this study, we utilized depth data collected from two blue sharks using pop-up satellite archival tags, and modelled the proportion of time the sharks were swimming in the top 1-meter layer and could therefore be detected by observers conducting aerial surveys. The availability models indicated that the tagged sharks preferred surface waters whilst swimming over the continental shelf and during daytime, with a model-predicted average proportion of time spent at the surface of 0.633 (SD = 0.094) for on-shelf, and 0.136 (SD = 0.075) for off-shelf. These predicted values were then used to account for availability bias in abundance estimates for the species over a large area in the Northeast Atlantic, derived through distance sampling using aerial survey data collected in 2015 and 2016 and modelled with density surface models. Further, we compared abundance estimates corrected with model-predicted availability to uncorrected estimates and to estimates that incorporated the average time the sharks were available for detection. The mean abundance (number of individuals) corrected with modelled availability was 15,320 (CV = 0.28) in 2015 and 11,001 (CV = 0.27) in 2016. Depending on the year, these estimates were ~7 times higher compared to estimates without the bias correction, and ~3 times higher compared to the abundances corrected with average availability. When the survey area contains habitat heterogeneity that may affect surfacing patterns of animals, modelling animals' availability provides a robust alternative to correcting for availability bias and highlights the need for caution when applying "average" correction factors.

The Importance of Marine Predators in the Provisioning of Ecosystem Services by Coastal Plant Communities

Food web theory predicts that current global declines in marine predators could generate unwanted consequences for many marine ecosystems. In coastal plant communities (kelp, seagrass, mangroves, and salt marsh), several studies have documented the far-reaching effects of changing predator populations. Across coastal ecosystems, the loss of marine predators appears to negatively affect coastal plant communities and the ecosystem services they provide. Here, we discuss some of the documented and suspected effects of predators on coastal protection, carbon sequestration, and the stability and resilience of coastal plant communities. In addition, we present a meta-analysis to assess the strength and direction of trophic cascades in kelp forests, seagrasses, salt marshes, and mangroves. We demonstrate that the strength and direction of trophic cascades varied across ecosystem types, with predators having a large positive effect on plants in salt marshes, a moderate positive effect on plants in kelp and mangroves, and no effect on plants in seagrasses. Our analysis also identified that there is a paucity of literature on trophic cascades for all four coastal plant systems, but especially seagrass and mangroves. Our results demonstrate the crucial role of predators in maintaining coastal ecosystem services, but also highlights the need for further research before large-scale generalizations about the prevalence, direction, and strength of trophic cascade in coastal plant communities can be made.

Current status of the megabenthic community in coastal Fukushima Prefecture, Japan, in the wake of the Great East Japan Earthquake

We conducted fisheries-independent bottom-trawl surveys along the coast of Fukushima, Japan, from 2013 to 2017 to study the megabenthic community structure after the 2011 earthquake, tsunami, and nuclear disaster. Although we observed no substantial changes in biodiversity, total abundance and biomass fluctuated among years, primarily because of temporary increases in the abundance or biomass of small shrimp and squid, or variations in abundance or biomass of mid-sized fishes (i.e. puffers and flatfishes) and large elasmobranchs. Echinoderm abundance and biomass decreased in all areas. Crustacean abundance and biomass were extremely low in the central and southern offshore transects. Our results suggest that there has been no recognizable recovery in the megabenthic community, and megabenthic species off the coast of Fukushima might have been experiencing reproductive or recruitment failure. Further research is needed to reveal the causal factors behind changes in these megabenthic communities.

Ocean warming has a greater effect than acidification on the early life history development and swimming performance of a large circumglobal pelagic fish

Ocean warming and acidification are serious threats to marine life; however, their individual and combined effects on large pelagic and predatory fishes are poorly understood. We determined the effects of projected future temperature and carbon dioxide (CO₂ ) levels on survival, growth, morphological development and swimming performance on the early life stages of a large circumglobal pelagic fish, the yellowtail kingfish Seriola lalandi. Eggs, larvae and juveniles were reared in cross-factored treatments of temperature (21 and 25°C) and pCO₂ (500 and 985 μatm) from fertilisation to 25 days post hatching (dph). Temperature had the greatest effect on survival, growth and development. Survivorship was lower, but growth and morphological development were faster at 25°C, with surviving fish larger and more developed at 1, 11 and 21 dph. Elevated pCO₂ affected size at 1 dph, but not at 11 or 21 dph, and did not affect survival or morphological development. Elevated temperature and pCO₂ had opposing effects on swimming performance at 21 dph. Critical swimming speed (U_crit ) was increased by elevated temperature but reduced by elevated pCO₂ . Additionally, elevated temperature increased the proportion of individuals that responded to a startle stimulus, reduced latency to respond and increased maximum escape speed, potentially due to the more advanced developmental stage of juveniles at 25°C. By contrast, elevated pCO₂ reduced the distance moved and average speed in response to a startle stimulus. Our results show that higher temperature is likely to be the primary driver of global change impacts on kingfish early life history; however, elevated pCO₂ could affect critical aspects of swimming performance in this pelagic species. Our findings will help parameterise and structure fisheries population dynamics models and improve projections of impacts to large pelagic fishes under climate change scenarios to better inform adaptation and mitigation responses.

Static Dental Disparity and Morphological Turnover in Sharks across the End-Cretaceous Mass Extinction

The Cretaceous-Palaeogene (K-Pg) mass extinction profoundly altered vertebrate ecosystems and prompted the radiation of many extant clades [1, 2]. Sharks (Selachimorpha) were one of the few larger-bodied marine predators that survived the K-Pg event and are represented by an almost-continuous dental fossil record. However, the precise dynamics of their transition through this interval remain uncertain [3]. Here, we apply 2D geometric morphometrics to reconstruct global and regional dental morphospace variation among Lamniformes (Mackerel sharks) and Carcharhiniformes (Ground sharks). These clades are prevalent predators in today's oceans, and were geographically widespread during the late Cretaceous-early Palaeogene. Our results reveal a decoupling of morphological disparity and taxonomic richness. Indeed, shark disparity was nearly static across the K-Pg extinction, in contrast to abrupt declines among other higher-trophic-level marine predators [4, 5]. Nevertheless, specific patterns indicate that an asymmetric extinction occurred among lamniforms possessing low-crowned/triangular teeth and that a subsequent proliferation of carcharhiniforms with similar tooth morphologies took place during the early Paleocene. This compositional shift in post-Mesozoic shark lineages hints at a profound and persistent K-Pg signature evident in the heterogeneity of modern shark communities. Moreover, such wholesale lineage turnover coincided with the loss of many cephalopod [6] and pelagic amniote [5] groups, as well as the explosive radiation of middle trophic-level teleost fishes [1]. We hypothesize that a combination of prey availability and post-extinction trophic cascades favored extant shark antecedents and laid the foundation for their extensive diversification later in the Cenozoic [7-10].

Scene through the eyes of an apex predator: a comparative analysis of the shark visual system

The eyes of apex predators, such as the shark, have fascinated comparative visual neuroscientists for hundreds of years with respect to how they perceive the dark depths of their ocean realm or the visual scene in search of prey. As the earliest representatives of the first stage in the evolution of jawed vertebrates, sharks have an important role to play in our understanding of the evolution of the vertebrate eye, including that of humans. This comprehensive review covers the structure and function of all the major ocular components in sharks and how they are adapted to a range of underwater light environments. A comparative approach is used to identify: species-specific diversity in the perception of clear optical images; photoreception for various visual behaviours; the trade-off between image resolution and sensitivity; and visual processing under a range of levels of illumination. The application of this knowledge is also discussed with respect to the conservation of this important group of cartilaginous fishes.

Dietary composition of black drum Pogonias cromis in a hypersaline estuary reflects water quality and prey availability

The Baffin Bay estuary is a hypersaline system in the Gulf of Mexico that supports an important recreational and commercial fishery for black drum Pogonias cromis, a benthic predator. Seasonal measurements of water quality variables, benthic macrofauna densities and biomass, and determination of P. cromis food sources using stomach-content and stable-isotope analyses were carried out to determine how P. cromis food sources change with water quality and how this may affect P. cromis diet. Gut-content analysis indicated P. cromis selectively consumed bivalves Mulinia lateralis and Anomalocardia auberiana. Isotope compositions demonstrated that P. cromis relied on these benthic food resources produced in the Baffin Bay estuary year-round. Biomass and densities of these bivalves were influenced by changes in water quality variables, particularly salinity and dissolved oxygen. Thus, this paper demonstrates the relationship between water quality variables, benthic macrofauna, and their use as food resources by a carnivorous fish species, and emphasizes the need for integrated assessments when studying the effects of water quality on ecosystem function. Holistic approaches such as these can provide important information for management and conservation of fishery resources and can improve predictions of ecosystem response to climate variability.

The social construction of the value of wildlife: A green cultural criminological perspective

The trade in wildlife is not a new phenomenon. The earliest civilizations were linked to the trade in live animals and parts thereof, from the Egyptian pharaohs to aristocrats in the modern era. This article focuses on the history of the wildlife trade in order to understand the social construction of the value of wildlife. In dynamic social and cultural contexts, the meaning of wildlife changes. Historically, exotic animals and the products thereof were associated with social elites, but today, wildlife attracts people from all walks of life and a wide variety of live animals and products thereof are traded for functional, symbolic and social purposes. Increasing ecocentric and biocentric values in contemporary western society, however, may influence constructed demand patterns for wildlife in the near future. By integrating cultural criminological concepts with the social construction of green crimes, this article aims to understand constructed wildlife consumerism through the ages.

Drivers of reef shark abundance and biomass in the Solomon Islands

Remote island nations face a number of challenges in addressing concerns about shark population status, including access to rigorously collected data and resources to manage fisheries. At present, very little data are available on shark populations in the Solomon Islands and scientific surveys to document shark and ray diversity and distribution have not been completed. We aimed to provide a baseline of the relative abundance and diversity of reef sharks and rays and assess the major drivers of reef shark abundance/biomass in the Western Province of the Solomon Islands using stereo baited remote underwater video. On average reef sharks were more abundant than in surrounding countries such as Fiji and Indonesia, yet below that of remote islands without historical fishing pressure, suggesting populations are relatively healthy but not pristine. We also assessed the influence of location, habitat type/complexity, depth and prey biomass on reef shark abundance and biomass. Location was the most important factor driving reef shark abundance and biomass with two times the abundance and a 43% greater biomass of reef sharks in the more remote locations, suggesting fishing may be impacting sharks in some areas. Our results give a much needed baseline and suggest that reef shark populations are still relatively unexploited, providing an opportunity for improved management of sharks and rays in the Solomon Islands.