Influence of fishing activity over the marine debris composition close to coastal jetty

Influence of trophic overlaps and trophic niche amplitude on microplastic intake of fish species in shallow areas of a neotropical coastal lagoon

Plastic pollution is a global challenge that affects all marine ecosystems, and reflects all types of uses and activities of human society in these environments. In marine ecosystems, microplastics and mesoplastics interact with invertebrates and become available to higher predators, such as fish, which can ingest these contaminants. This study aimed to analyze how ecological food interactions (diet overlap and trophic niche amplitude) among fish species contribute to the ingestion of plastic particles. The gastrointestinal contents of six fish species (Atherinella brasiliensis, Eucinostomus melanopterus, Eucinostomus argenteus, Genidens genidens, Coptodon rendalli, and Geophagus brasiliensis) were analyzed to identify prey items and plastic ingestion. Based on the ontogenetic classification, A. brasiliensis, E. melanopterus, and G. genidens were divided into juveniles and adults, and the six fish species analyzed were divided into nine predator groups. Most of the plastics ingested by the fish species were blue microplastic (MP) fibers (< 0.05 mm) classified as polyester terephthalate, polyethylene, and polybutadiene. Considering all the analyzed predators, the average number and weight of plastics ingested per individual were 2.01 and 0.0005 g, respectively. We observed that predators with a high trophic overlap could present a relationship with the intake of MP fibers owing to predation on the same resources. In addition, we observed the general pattern that when a species expands its trophic diversity and niche, it can become more susceptible to plastic ingestion. For example, the species with the highest Levin niche amplitude, E. argenteus juveniles, had the highest mean number (2.9) of ingested MP fibers. Understanding the feeding ecology and interactions among species, considering how each predator uses habitats and food resources, can provide a better understanding of how plastic particle contamination occurs and which habitats are contaminated with these polluting substances.

Plastic ingestion by three species of Scylla (Brachyura) from the coastal areas of Thailand

This study marked the first investigation into the presence of plastic particles in the stomachs of three mud crab species (Scylla olivacea, S. paramamosain and S. tranquebarica) collected across the Andaman Sea and the Gulf of Thailand. The highest number of plastic particles in the stomach of crab samples was polyethylene (PE) that contributed 88.5 %; while green was the predominant colour (60.3 %). Ingested particles recovered from the stomachs of crabs differed significantly between species and sites (p < 0.001). The average number of plastic particles per individual was 2.3 ± 8.6 in Scylla olivacea, 7.2 ± 16.9 in S. paramamosain, and 13.5 ± 48.9 in S. tranquebarica. Satun, revealed the highest number of plastic particles recovered from mud crabs, while the lowest number of plastic particles were from Pattani. To conclude, species of crab and site of collection plays a crucial factor in the propensity of plastic particles ingested by the genus Scylla mud crabs.

A lesser known but emerging issue, recreational fishing debris and the anglers' opinions in South Korea

The abundance and characteristics of marine debris originating from recreational fishing were examined across 55 sites in four different regions in Korea. The result shows that the average abundance of debris was 4.3 ± 4.2 (n/m2) in terms of the number and 13.4 ± 18.1 (g/m2) in terms of the weight, and the most often found item was fishing lines (<1 m). Detrimental fishing debris such as fishing lines, hooks and weights comprised 50.9 % of the total debris, suggesting significant impacts on wildlife. A questionnaire survey was conducted with 374 anglers across all four regions to understand their behaviors, perceptions, and preferences regarding government policies. Most of the respondents were aware of the adverse impacts of recreational fishing debris on the environment, and >50 % agreed with the introduction of recreational fishing licenses. This study highlights the urgent need to raise awareness and address the undervalued problem of recreational fishing debris.

Plastic ingestion by carnivore fish in a neotropical floodplain: seasonal and interspecific variations

Some studies have shown that freshwater ecosystems are polluted in a similar proportion to marine ecosystems; however, there are many gaps to be filled in this topic. Here, we investigated whether plastics were consumed by carnivore fishes in a Neotropical floodplain and whether it was connected to seasonality (dry and wet seasons). We also evaluated the association between each type of plastic and the fish species. We analyzed the gastrointestinal contents of 23 species and assessed the occurrence and number of plastic particles. Plastics were obtained through chemical digestion and the spectrum of each sample, using a FT-IR imaging microscope. We performed a correspondence analysis (CA) with plastic data to assess the relationship between each type of plastic and the fish species. We also performed linear regression models to assess the relationships of occurrence and number of plastics ingested with seasonality. Nine species had plastics in their gastrointestinal contents, and they were identified as polyvinyl alcohol (PVA), polyamide (PA), polyethylene (PE), polystyrene (PS), and polypropylene (PP). The number of plastics had a positive relationship with the wet season, while the occurrence did not show a significant relationship with any season. These results are particularly important when considering the socioeconomic relevance and the ecological importance of this trophic guild.

Piers are hotspots for benthic marine debris in an urbanised estuary

Records of anthropogenic marine debris and the threats it poses are increasing worldwide, yet we know relatively little about the distribution of benthic debris. The seafloor is the final destination for a large proportion of debris due to the degradation and sinking of items. A more detailed understanding of debris distributions in hotspots such as urbanised estuaries can help decision makers target management and remediation activities. We selected sites frequented by fishers and boaters in Sydney Harbour, an urbanised estuary, to investigate the impacts of recreational activities on debris abundance. The aim of this study was to examine variation in macro debris (>5mm in diameter) type and abundance at two habitat types (piers and non-piers). We chose five locations at various distances from the estuary mouth. In each location SCUBA teams performed fixed transects at two sites, one under a pier and one over nearby soft-sediment habitat. Debris was recovered by the divers and brought to the surface for classification and disposal. Surveys were repeated multiple times at each location between November 2019 and February 2020, recording a total of 2803 debris items over 36 survey events. Overall, piers had more than ten times the debris abundance of soft-sediment sites, and much higher proportion of debris types related to recreational fishing. Over half of the debris items in this study were plastic (65%), and approximately 70% of the total debris was classified as related to recreational fishing. This trait was most prominent in debris at sites closest to the estuary mouth, likely reflecting increased fishing activity in this area. This study indicates that policy makers and community groups in urbanised estuaries should focus monitoring, reduction, and remediation efforts near artificial structures such as piers, and that public awareness campaigns should target the behaviour of recreational users of these structures.

Composition and spatial distribution of floating plastic debris along the estuarine ecocline of a subtropical coastal lagoon in the Western Atlantic

With the objective of characterizing the composition and spatial distribution of plastic fragments in a subtropical lagoon system, five sample areas affected by various anthropogenic impacts were chosen in the southern part of the Estuarine Lagoon System in Laguna, Santa Catarina, Brazil. The total density of the floating meso- and microplastics encountered was 7.32/m³, with the greatest density in the access channel and external area of the lagoon. Plastic filament was the most abundant and mainly comprised polyester (PET), polypropylene (PP) and polyethylene (PE) from 0.05 to 0.71 mm². Fishing and urbanization were the main sources of the meso- and microplastics in the environment. This is the first study to evaluate contamination by meso- and microplastics in the southern part of the Estuarine Lagoon System and provides information about the nature and extent of contamination by plastics in this estuarine ecosystem.

Source, fate and management of recreational fishing marine debris

Marine debris, directly and indirectly, threatens marine habitat and biota. Fishing activity is generally recognised as a contributor to marine debris, but the relative input from recreational fishing remains unassessed. Here we provide the first comprehensive literature review of recreational fishing marine debris (RFMD) on a global scale. A systematic literature review identified 70 studies related to RFMD, and plastic and metal respectively were the dominant debris materials found. Nearshore coastal areas and reefs, acted as both sources and sinks of RFMD and a diverse suite of potential impacts such as ghost fishing and entanglement were identified at local scales. Overall, research of RFMD is lacking globally, however, its role in marine debris input is likely underestimated. We recommend more research on the volumes and risks, using a standardised classification approach. Where intervention is required, we suggest cooperative approaches between the sector and authorities.

Fishing plastics: A high occurrence of marine litter in surf-zone trammel nets of Southern Brazil

Plastic is one of the most commonly found residues in the marine environment, which can cause several impacts. This study evaluated the interaction of marine litter with surf-zone trammel nets in Southern Brazil. Fifty fishing operations were sampled, where 4213 items were captured: 1500 discarded fish, 1384 fragments of marine litter, and 1329 utilized fishes. Plastics were the most abundant items (n = 1363), representing 98.4% of the registered marine litter, especially plastic bags (n = 1191). 94.5% of registered marine litter is considered as single-use waste. The interaction with marine litter can cause negative impacts to small-scale fisheries (e.g. economic and damage to fishing nets). We highlight the urgency in implementing actions for urban solid waste management and public policies to reduce single-use plastics and educational campaigns on the environmental theme.

Occurrence, abundance, and distribution of microplastics pollution: an evidence in surface tropical water of Klang River estuary, Malaysia

Microplastics have been considered as contaminants of emerging concern due to ubiquity in the environment; however, the occurrence of microplastics in river estuaries is scarcely investigated. The Klang River estuary is an important ecosystem that receives various contaminants from urbanised, highly populated areas and the busiest maritime centre in Selangor, Malaysia. This study investigates the abundance and characteristics of microplastics in surface water of the Klang River estuary. The abundance of microplastics ranged from 0.5 to 4.5 particles L^-1 with a mean abundance of 2.47 particles L^-1. There is no correlation between the abundance of microplastics and physicochemical properties, while there is a strong correlation between salinity and conductivity. The microplastics were characterised with a stereomicroscope and attenuated total reflection-Fourier transform infrared spectroscopy to analyse size, shape, colour, and polymer composition. The microplastics in the surface water were predominantly in the 300-1000 μm size class, followed by > 1000 μm and < 300 μm, and were mostly transparent fibres, fragments, and pellets. Polyamide and polyethylene were the main polymer types in the composition of the microplastics, suggesting that the microplastics originated from heavily urbanised and industrial locations such as the port, jetty, and residential areas. The widespread occurrence of microplastics in the environment and subsequent penetration of aquatic food webs may pose a serious threat to organisms. This study provides baseline data and a framework for further investigation of microplastic contamination in estuaries.

When an advantageous reproductive trait turns bad: Eggs of the threatened fish Genidens barbus as a natural bait in recreational fisheries

This study describes a recreational fishing method focused on marine catfish, Genidens barbus (Endangered-EN), through the adoption of its eggs as a natural bait during its reproductive period in southern Brazilian ecosystems. Male G. barbus perform parental care, collecting eggs released by females after the fertilization process. Owing to this male behavioural pattern during the reproductive period, these individuals are easily caught in recreational fisheries that use eggs of the same species as a natural bait. The current adoption of G. barbus eggs as bait may intensify the fishing pressure on its populations.

Marine debris - An emerging threat to the reef areas of Gulf of Mannar, India

Underwater survey was conducted to assess the accumulation and impact of marine debris in the reef areas of Gulf of Mannar in southeast India. A combination of roving diver technique and belt transect method was applied for the assessment, which was conducted during the period between February 2018 and March 2019. An estimated total reef area of 1152 m² has been affected by marine debris. Abandoned fishing nets were found to constitute the major portion of 43.17 ± 5.48% of the marine debris. Live corals were found to be dominant substrates for marine debris with 39.11%. The average prevalence of coral colonies in contact with marine debris was 3.28 ± 0.27%. Prevalence of corals in contact with debris was very high in genus Acropora with 8.23 ± 1.29% followed by Montipora with 4.63 ± 1.29% due to their complex growth form. Of the corals in contact with debris, 47.56% were fragmented and 34% were found with tissue loss.

Ingestion of plastic fragments by the Guri sea catfish Genidens genidens (Cuvier, 1829) in a subtropical coastal estuarine system

One of the most recognized anthropogenic impacts in marine environments is solid waste pollution, especially plastic, which can be ingested by fish, thus interfering with their health. In this context, the aim of this study is to describe the ingestion of plastic fragments and to identify the possible effect of this contamination in the condition factor of Genidens genidens in the Laguna Estuarine System. The stomach contents of 92 G. genidens (26 juveniles and 66 adults) were analyzed. The Index of Relative Importance was performed to identify the contribution of each prey item. Condition factor (CF) was used to analyze the effect of plastic ingestion on the fish's body condition (by comparing individuals in the same ontogenetic phase). For the juveniles, eight items were observed, the most important of which were Penaeidae, followed by Portunidae and plastic. For the adults, 12 items were observed, the most important of which were Penaeidae, Portunidae, Polychaeta, and plastic. The analysis of CF demonstrated higher values for individuals without plastic in the stomach, which indicated a better health condition. The CF of a fish may be affected by variations in the physiological condition, environmental stresses, and nutritional and biological variations, and could be used to compare the body condition or health of a fish species. The ingestion of plastic could significantly influence the worst body condition of the individuals that were analyzed in the present study. The plastic pollution in marine coastal waters is associated with the appropriate waste management levels.

Pollution and coral damage caused by derelict fishing gear on coral reefs around Koh Tao, Gulf of Thailand

Most lost fishing gear is made of non-biodegradable plastics that may sink to the sea floor or drift around in currents. It may remain unnoticed until it shows up on coral reefs, beaches and in other coastal habitats. Stony corals have fragile skeletons and soft tissues that can easily become damaged when they get in contact with lost fishing gear. During a dive survey around Koh Tao, a small island in the Gulf of Thailand, the impact of lost fishing gear (nets, ropes, cages, lines) was studied on corals representing six different growth forms: branching, encrusting, foliaceous, free-living, laminar, and massive. Most gear (>95%) contained plastic. Besides absence of damage (ND), three categories of coral damage were assessed: fresh tissue loss (FTL), tissue loss with algal growth (TLAG), and fragmentation (FR). The position of the corals in relation to the fishing gear was recorded as either growing underneath (Un) or on top (On), whereas corals adjacent to the gear (Ad) were used as controls. Nets formed the dominant type of lost gear, followed by ropes, lines and cages, respectively. Branching corals were most commonly found in contact with the gear and also around it. Tubastraea micranthus was the most commonly encountered coral species, either Un, On, or Ad. Corals underneath gear showed most damage, which predominantly consisted of tissue loss. Fragmentation was less common than expected, which may be related to the low fragility of T. micranthus as dominant branching species. Even if nets serve as substrate for corals, it is recommended to remove them from reefs, where they form a major component of the plastic pollution and cause damage to corals and other reef organisms.