Ecosystem-based management approaches for watershed conservation and geosustainability

When contributors' goals and legislative and political structures vary, as they often do in the case of worldwide fish populations, it becomes more challenging to implement ethical fishing tactics. Canada, the United States, and Mexico all fish from Pacific regions anchovies in the California Modern. Climate-driven numbers and geographic dynamics may pollute the waters of collaborative aquaculture and lead to overloading. This research expands upon prior works using a game theoretic model of Tran's boundary sardine fisheries in different climatic conditions to account for ecological links. More significant economic advantages accrue from cooperation fishing tactics that consider the mackerel's role as feed for other species in the natural system, as opposed to plans that merely take note of the worth of mackerel harvests to a particular fishing nation. The maximum environmental benefit is obtained at a fishery rate for sardines barely less than the sardine Fishery Management Safe Yield. Ecological-based control of fisheries can increase sustainability and profits, but only if investors and policy makers consider the ecology in business-applicable models. Understanding and adapting to the fast alterations in habitat distributions due to climate change and designing ways to achieve viable and lucrative fishery amidst altering environments will necessitate an increased emphasis on ecosystem-based governance.

Atlantic bonito (Sarda) genomic analysis reveals population differentiation across Northeast Atlantic and mediterranean locations: Implications for fishery management

The Atlantic bonito (Sarda, family Scombridae) is a pelagic species and one of the most exploited small tuna species. Despite its economic importance, biological information is scarce with no associated management directives. In this study, using a population genomic approach resulted in a lack of panmixia of two genetic pools with different effective population sizes (east central-tropical Atlantic and northeast Atlantic-Mediterranean) and an intermixing zone in Atlantic Morocco. The absence of genetic heterogeneity between the locations in Atlantic - Mediterranean transitional zone adds new evidence that challenges the Strait of Gibraltar as a phylogeographic barrier for marine pelagic species. These results are proposed to the ICCAT Commission to establish management areas for this species, although they are not consistent with the recently adopted pelagic ecoregions. Finally, a panel of highly informative SNPs was developed for efficient and low-cost population assignment and the analysis of unresolved population structures.

Monitoring and management of abandoned, lost and discarded fishing gear (ALDFG) in Penghu Islands, Taiwan

This study investigated the conditions of abandoned, lost, discarded fishing gear (ALDFG) in natural and artificial reef zones and removed it afterward in Penghu Islands. Various feasible suggestions for improving ALDFG management were proposed for the county government to manage and reduce the generation of ALDFG in the future and maintain the marine ecosystem. This study divided the ocean areas of Penghu into five sub-areas for carrying out research and surveys. 165 boat trips of ALDFG investigation and removal were conducted from July 2018 to October 2019. The results show the ALDFG in natural reef areas is mostly large-mesh gillnets (26 %). The rest are single-layer bottom gillnets (21 %) and multi-layer bottom gillnets (20 %). In line with the recent efforts of the Penghu County Government to address ALDFG, it is recommended that the participation of citizen scientists and the promotion of ocean education can be utilized for fishery co-management in Penghu.

A model of a fishery with fish storage and variable price involving delay equations

We propose a bio-economic model of a fishery describing the variations of the fish stock, the fishing effort and the price of the resource on the market supposed to depend on supply and demand. The originality of this model comes from taking into account the storage of part of the resource for a certain time before being put up for sale on the market. Taking into account the supposedly fast price dynamics compared to the other mechanisms involved and after integration of the stock equation, the system is reduced to a system of two delayed differential equations. The qualitative analysis of the model is carried out with the search for equilibrium points and the study of their stability. The study shows the existence of a catastrophic equilibrium corresponding to the extinction of the resource and one or two sustainable fishery equilibrium points that can coexist under certain conditions. The model shows that storing part of the resource makes it possible to avoid a catastrophic situation with the extinction of the fish stock and to stabilize the fishery in the long term. The study also shows that the price variation of the resource has a stabilizing effect by avoiding the appearance of periodic solutions associated with a stable limit cycle surrounding a sustainable fishery equilibrium point resulting from a Hopf bifurcation, which is contrary to the case without price variation where this is possible.

Evaluation and quantification of shell damage and survival of the striped venus clam (Chamelea gallina) harvested by hydraulic dredges

The impact of hydraulic dredging on Chamelea gallina populations in the mid-western Adriatic Sea was assessed by evaluating and quantifying the damage exerted on harvested (non-sieved) and sorted (sieved by the mechanical vibrating sieve: commercial or discarded) individuals and by estimating the survival probability of discarded clams. The results showed that: i) dredging had a higher impact on determining shell damage than the mechanical vibrating sieve, ii) damage probability was strongly associated with shell length and in discard samples the effect of the shell length was greater due to the longer time spent by the individuals inside in the vibrating sieve before being rejected to the sea, iii) the survivability of the entire discarded fraction of clams was high. The findings support the Regulation (CE) 1380/2013 which foresees that discards from the Venus clam fishery must be returned to the sea and shall not be landed.

Exploring governance policy of marine fishery litter in China: Evolution, challenges and prospects

With great economic loss and environmental hazards, litter derived from marine fishery production has been a worldwide problem and has risen common concerns. China is no exception. The government of China has made an effort in the marine fishery litter governance since 1982 by issuing policy documents. This study reviews relevant policies from 1982 to 2021 and analyzes them to improve marine fishery litter governance. Three stages can be divided: The initial formation period (1982-2006), the exploratory governance period (2006-2016), and the fine development period (2016-present). The marine fishery litter governance policy system has been continuously improved, but the rough governance link joins, vague responsibility partition and insufficient coordination, and technology and knowledge pose challenges to the policy implementation. Finally, prospects on marine fishery litter governance policy formulation and implementation are put forward.

Conservation connections: incorporating connectivity into management and conservation of flats fishes and their habitats in a multi-stressor world

Coastal marine fisheries and the habitats that support them are under extensive and increasing pressures from numerous anthropogenic stressors that occur at multiple spatial and temporal scales and often intersect in unexpected ways. Frequently, the scales at which these fisheries are managed do not match the scales of the stressors, much less the geographic scale of species biology. In general, fishery management is ill prepared to address these stressors, as underscored by the continuing lack of integration of fisheries and habitat management. However, research of these fisheries is increasingly being conducted at spatial and temporal scales that incorporate biology and ecological connectivity of target species, with growing attention to the foundational role of habitat. These efforts are also increasingly engaging stakeholders and rights holders in research, education, and conservation. This multi-method approach is essential for addressing pressing conservation challenges that are common to flats ecosystems. Flats fisheries occur in the shallow, coastal habitat mosaic that supports fish species that are accessible to and desirable to target by recreational fishers. Because these species rely upon coastal habitats, the anthropogenic stressors can be especially intense-habitat alteration (loss and degradation) and water quality declines are being exacerbated by climate change and increasing direct human impacts (e.g., fishing effort, boat traffic, depredation, pollution). The connections necessary for effective flats conservation are of many modes and include ontogenetic habitat connectivity; connections between stressors and impacts to fishes; connections between research and management, such as research informing spawning area protections; and engagement of stakeholders and rights holders in research, education, and management. The articles included in this Special Issue build upon a growing literature that is filling knowledge gaps for flats fishes and their habitats and increasingly providing the evidence to inform resource management. Indeed, numerous articles in this issue propose or summarize direct application of research findings to management with a focus on current and future conservation challenges. As with many other fisheries, a revised approach to management and conservation is needed in the Anthropocene.

A review of the knowledge of reef fish in the Southwest Atlantic

Reef environments are rapidly transforming worldwide, and these changes are causing major impacts to the reef ecosystem. Scientific knowledge is strategic for marine conservation and management in these scenarios. Aiming to contribute to this subject, a systematic review from 1967 to 2020 was conducted, in order to identify gaps in studies regarding reef fish species, ecosystem components and processes. Multidisciplinary sciences concerning reef fish have been rising, mainly in the fields of basic biology and ecology. Besides that, phase shifts and ecosystem services were absent terms in the analyzes of co-occurrence. Research in the ethnosciences needs to be increased, and will improve access to local ecological knowledge, which can be used as a tool to address issues in reef environments. Socio-ecological systems are components of this landscape that has had few publications. The participation in the elaboration of public policies can be a new avenue to foster the biodiversity of reef environments.

A mesoscale analysis of relations between fish species richness and environmental and anthropogenic pressures in the Mediterranean Sea

Although there is a great knowledge about individual anthropogenic threats to different fish species in the Mediterranean Sea, little is known about how these threats accumulate and interact to affect fish species richness in conjunction with environmental dynamics. This study assesses the role of these threats in the fish richness component and identifies the main areas where the interaction between fish species richness and threats is highest. Our results show that fish richness seems to be higher in saltier and colder areas where the chlorophyll-a and phosphate concentrations are lower. Among the anthropogenic threats analyzed, the costal impact and the fishing effort seems to be the more relevant ones. Overall areas with high fish richness are mainly located along the western and northern shores, with lower values in the south-eastern regions. Areas of potential high cumulative threats are widespread in both the western and eastern basins, with fewer areas located in the south-eastern region. By describing the spatial patterns of the fish richness and which drivers explain these patterns we can also identify which anthropogenic activities can be managed more effectively to maintain and restore marine fish biodiversity in the basin.

Estimation and use of recreational fishing values in management decisions

In many countries, commercial and recreational fishing compete for access to marine resources. In some cases, recreational catch outweighs commercial harvest and may threaten species otherwise protected from commercial fishing. This has led to increasing calls for improved management of recreational fishing in the broader context of general fisheries management. As a result, fisheries managers face the challenge to decide how to allocate the available marine resources between competing uses. In this paper, we review and explain two common approaches that have been used to support recreational fishing allocation decisions. While economic activity analysis is an appropriate tool to assess how a change in resource allocation would affect regional economic activity (economic contributions and impacts), it is ill-suited to assess associated gains or losses in welfare of society as a whole (economic efficiency). Hence, economic activity analysis and social cost-benefit analysis complement each other, with each providing a different set of information answering a different set of questions. Unfortunately, both types of analysis use the term "economic value" suggesting that they are alternative approaches that provide the same information, whereas in fact they are not. If the objective of fishery managers is to ensure that society as a whole is made better off, the appropriate metric is economic value as defined by welfare economics. Under this definition, all goods and services provided by marine resources that are beneficial to humans have economic value. This includes non-use values such as the continued existence of an endangered marine species. The aim of this paper is to support managers and policymakers in allocating marine resources by reviewing relevant economic principles, concepts, and tools in the context of recreational fishing, including the use and challenges of estimating the non-market benefits generated by recreational fishing experiences.

The impact of potting for crustaceans on temperate rocky reef habitats: Implications for management

Multi-use marine protected areas (MPAs) are increasingly designated towards achieving global conservation targets. To develop effective management, the impact of permitted activities must be understood. Potting for shellfish occurs on temperate rocky reefs globally with impact not fully quantified. This UK-based study used underwater video to quantify (a) benthic condition of rocky reefs, (b) mechanisms of potting interaction and (c) true footprint of potting. Assemblages in static gear areas were more indicative of a healthy reef than those in mixed gear areas. Damage was recorded during pot hauling, but the area of damage was not the entire pot haul path. 25-30% of individuals were damaged (commonly through tissue abrasion) or removed. Notably, damage occurred to some long-lived, slow growing taxa raising concerns over impacts. Potting is more destructive than previously thought and managers must balance ecology with social and economic considerations to determine what level of impact is acceptable.

Ichthyo-diversity assessment of the Old Brahmaputra river, Bangladesh: present stance and way forward

The study was carried out to obtain information on the present status and trend of finfish diversity of the Old Brahmaputra river, Bangladesh. Samples were collected directly from a professional fishing boat caught by different nets, traps and hooks from January 2019 to December 2019. Together with 4 exotic species, a total of 49 species under 6 families were recorded. Though a biodiversity index of 3.65854 and a dominance index of 0.030929 represent the richness of ichthyo-diversity within the river, Synbranchiformes and Tetraodontiformes were not reported throughout the study period. Linear regression analysis showed a positive correlation between water height of the river and monthly abundance of the species found. Catch composition of catfishes and snakeheads slumped while barbs showed triumph over previous findings. A majority of fish recorded were within the least concern category according to IUCN (2015) but portions also belonged to critically endangered, endangered, and vulnerable categories as well. Therefore, conservation measures must be infixed in the Old Brahmaputra river to hold the fish diversity in a sustainable state.

Identifying peak breeding season and estimating size at first maturity of mud crab (Scylla olivacea) from a coastal region of Bangladesh

Recently mud crab (Scylla olivacea) has emerged as a potential export commodity. Its farming is increasing rapidly in Bangladesh because of its lucrative price and high demand in international market. However, the farming or fattening of mud crab is totally dependent on capture of wild crablets. A huge quantity of mud crabs is being caught indiscriminately from nature and thus putting intense pressure on its wild stock, which is a major concern of conservation. Imposing ban at peak breeding season and setting a legal capture size are considered effective management tools for safe migration and spawning of berried females. There is contradictory information on breeding season of mud crab in Bangladesh. Thus, it is crucial to identify the peak breeding season of it and to formulate conservation policies to protect the berried crabs. Live crabs were collected year-round from the river adjacent to southwest part of Sundarbans. Although mud crab breeds throughout the year, March-April was identified as the peak breeding season of it. The second peak was observed in August-September. The highest abundance of crablets (1-2 months age) was recorded in May-June, and the lowest in January-February. Immature crablets were found all through the year that proves that mud crab is a continuous breeder. The highest amount of GSI value (11.6) was observed in February-March, which indicates that the breeding is very near. The size at first maturity (M₅₀) was estimated as 95.5 mm CW which lied at size class 91-100 mm (CW). The findings from the study will assist in fixing up the banning time and thus protecting the mother crabs; and will assist in formulating police to conserve and protect juvenile crabs in the sense that the minimum legal capture size of crabs will allow the adults to mate and spawn at least once before their capture.

Spatially explicit modeling of metapopulation dynamics of broadcast spawners and stabilizing/destabilizing effects of heterogeneity of quality across local habitats

Many coastal invertebrate species are broadcast spawners. These species have a highly sedentary adult stage and disperse by oceanic transport of planktonic larvae. One commercially important group of broadcast spawners is abalones, which live in suitable habitat patches of rock reefs that are discretely distributed. Because of these life-history and habitat characteristics, abalones tend to exhibit a metapopulation structure. Despite fisheries management and the release of juveniles, wild populations of broadcast spawners have undergone dramatic reductions in density due to overexploitation, which has been partly attributed to a failure to account for spatial structure. To clarify the relationship between the persistence of a metapopulation and the bottleneck that occurs during reproduction and dispersal processes caused by spatial structure, we developed a spatially explicit metapopulation model accounting for the effects of both life history and fishery pressure. By analyzing the model, we derived a metric to evaluate metapopulation quality as the leading eigenvalue of a non-negative matrix (the landscape matrix). Using this measure, we clarified that the effect of spatial structure on metapopulation stability is explained well by the mean and variance of parameter values across patches under the condition in which the heterogeneity of the metapopulation network is weak. In particular, the presence of both a higher average and higher variance of quality in the landscape could indicate stable fishery stocks under certain conditions. For example, when the decline in the mean longevity of local patch due to the fishery pressures gradually diminishes, the rescue effects by good patches would work more effectively than the negative effect of bad patches and then the stabilizing effect of spatial heterogeneity could be observed in a metapopulation. Furthermore, optimal patch characteristics for the improvement of quality strongly depend on specific parameter values. For example, when adult fertility is improved, a patch with higher "source" ability is more suitable. In contrast, when the settlement success of planktonic larvae is improved or fishery pressure is reduced, a patch with higher "buffer" ability is more suitable for the improvement of fishery management.

Small-sized and well-enforced Marine Protected Areas provide ecological benefits for piscivorous fish populations worldwide

Many piscivorous fish species are depleted and/or threatened around the world. Marine Protected Areas (MPAs) are tools for conservation and fisheries management, though there is still controversy regarding the best design for increasing their ecological effectiveness. Here, on the basis of a weighted meta-analytical approach, we have assessed the effect of 32 MPAs, distributed worldwide, on the biomass and density of piscivorous fishes. We analysed the MPA features and the biological, commercial and ecological characteristics of fishes that may affect the response of species to protection. We found a positive effect on the biomass and density of piscivores inside MPAs. This effect was stronger for the biomass of medium-sized fishes (in relation to the maximum size reported for the species) and the density of large and gregarious species. The size of the no-take zone had a significant negative impact on both response variables and differed according to the level of enforcement, with smaller no-take zones having higher levels of enforcement. Thus, MPAs help to protect piscivorous fish species, with smaller, but well enforced reserves being more effective for the protection of the local populations of piscivorous fishes throughout the world.

Contemporary changes in structural dynamics and socioeconomic drivers of inland fishery in China

Dynamics of inland fishery remain poorly understood despite their increasing socioeconomic importance and rapid growth. Here we analyze the changes in the dynamics of Chinese traditional and new inland fisheries by examining 26 years (1991-2016) of reported annual catch and mean trophic level in relation to socioeconomic development in China at provincial level. Results from spatial panel linear models indicate a significant correlation between socioeconomic and fishery variables, strongly suggesting that the development of these fisheries is nested in the socioeconomic context specific to each province. A preference towards higher trophic level species (i.e., investment in quality) is revealed under a status of socioeconomic wealth, while a focus on production (i.e., quantity) is observed when population, and therefore food demand, increases. By providing novel evidence on the links between large-scale dynamics in production and trophic structure of a country's inland fishery and the socioeconomic context driving the fish demand and consumption, our work represents an important contribution towards a broader assessment and management of inland fishery resources.

Effects of inconsistent reporting, regulation changes and market demand on abundance indices of sharks caught by pelagic longliners off southern Africa

The assumption of a proportional relationship between catch-per-unit-effort (CPUE) and the abundance of sharks caught by pelagic longliners is tenuous when based on fisher logbooks that report only retained specimens. Nevertheless, commercial logbooks and landings statistics are often the only data available for stock status assessments. Logbook data collected from local and foreign pelagic longline vessels operating in four areas off southern Africa between 2000 and 2015 were used to construct standardized CPUE indices for blue sharks Prionace glauca and shortfin makos Isurus oxyrinchus. Generalized linear mixed models were used to explore the effects of year, month, vessel, fleet and presence of an observer on blue shark and shortfin mako variability. Landing statistics and auxiliary information on the history of the fishery, regulation changes, and market factors were superimposed on the CPUE indices, to test hypotheses that they would influence CPUE trends. Indices in the West and Southwest (Atlantic) areas were elevated for both species, compared to the South and East (Indian Ocean). The scale of year-on-year CPUE increments, up to an order of magnitude for blue sharks, reflected occasional targeting and retention, interspersed with periods where blue sharks were not caught, or discarded and not reported. Increments were smaller for higher value shortfin makos, suggesting that indices were less affected by unreported discarding. CPUE indices and landings of both shark species have increased in recent years, suggesting increased importance as target species. Analysis of logbook data resulted in unreliable indicators of shark abundance, but when trends were interpreted in conjunction with landings data, disaggregated by area and month, and with hindsight of market demand and regulation changes, anomalies could be explained.

Potential medium-term impacts of climate change on tuna and billfish in the Gulf of Mexico: A qualitative framework for management and conservation

A systematic review of scientific papers on the potential impacts of climate-driven environmental changes on tuna and billfish in the Gulf of Mexico (GOM) was conducted to identify the climate-driven pressures and their associated potential impacts on the reproductive success and survival of tuna and billfish, and which of those impacts may have more relevance for their management and conservation in the GOM by 2050. An Impact Screening Analysis (ISA) was developed to evaluate the potential climate impacts discovered in the literature synthesis by assessing each impact against four criteria, and assigning it a ranking based on likelihood of occurrence (High, Medium, or Low). Results show three types of climate-driven pressures within the High ranking: increased water temperature; changes in ocean circulation and eddy kinetic energy; and changes in storm and wind patterns. Our findings provide valuable information to advance our understanding of key climate-driven physico-chemical processes that can impact the biology of tuna and billfish in the GOM, and enhance conservation and management of these species.

Quantification of the indirect effects of scallop dredge fisheries on a brown crab fishery

This study aimed to describe the characteristics of the by-catch of Cancer pagurus in king scallop dredges in the Isle of Man, and to determine the damage, immediate mortality and estimated mortality during fishing seasons associated with scallop dredges. Based on dredge surveys, spatial and seasonal variations were observed, with the highest number of crabs found off the west coast of the Isle of Man in the autumn when berried females crabs were most frequently caught. In general, female crabs comprised 84% of the catch. The damage levels of crabs was high with 45% of crabs recorded as crushed or dead or with severe damage, whilst 24% of crabs exhibited missing limbs. Estimates of the potential mortality associated with scallop dredging led to a lower and upper estimate of possible crab by-catch mortality of 15t and 24t respectively which represented 3.0-4.8% of the commercial landings of brown crab for the Isle of Man. Heaviest mortalities of crabs occurred in autumn to the west of the Isle of Man when female berried crabs move offshore into deeper water. The use of a temporary and spatially restricted scallop dredging closure could provide a simple solution to mitigate additional crab mortality in the event that scallop dredging increased beyond current levels in the future.

The state of the fishery, conservation and management of the stalked barnacle Pollicipes pollicipes in Portugal

The stalked barnacle Pollicipes pollicipes is the most important intertidal economical resource in Portugal. The assessment of the state of the fishery, conservation and management of P. pollicipes in Portugal was made for the first time in three regions with different regulations regarding this fishery: two marine protected areas ("Reserva Natural das Berlengas", RNB; and "Parque Natural do Sudoeste Alentejano e Costa Vicentina", PNSACV); and the Center coast. Different approaches (independent observations, inquiries, logbooks) and sources of data (past and recent) were used. An overall negative tendency of the state of the fishery and conservation of this resource was observed in all regions, with the exception of the stable tendency detected in PNSACV when using the inquiries approach. A weak management was considered to be in practice at Center and at PNSACV, while an acceptable management was inferred for RNB. We recommend a change into a co-management system that should be tested in pilot regions as RNB and/or PNSACV.

Out of sight but not out of mind: harmful effects of derelict traps in selected U.S. coastal waters

There is a paucity of data in the published literature on the ecological and economic impacts of derelict fishing traps (DFTs) in coastal ecosystems. We synthesized results from seven NOAA-funded trap fisheries studies around the United States and determined that DFT-caused losses to habitat and harvestable annual catch are pervasive, persistent, and largely preventable. Based on this synthesis, we identified key gaps to fill in order to better manage and prevent DFTs. We conclude with suggestions for developing a U.S. DFT management strategy including: (1) targeting studies to estimate mortality of fishery stocks, (2) assessing the economic impacts of DFTs on fisheries, (3) collaborating with the fishing industry to develop solutions to ghost fishing, and (4) examining the regional context and challenges resulting in DFTs to find effective policy solutions to manage, reduce, and prevent gear loss.