Coastal Fish Species Research Articles

Hyperoxia does not improve the acute upper thermal tolerance of a tropical marine fish (Lutjanus apodus).

Fish can experience hyperoxia in shallow environments due to photosynthetic activity and this has been suggested to provide them with a metabolic refuge during acute warming. However, this hypothesis has never been tested on a tropical marine species. Thus, we fitted 29°C-acclimated wild schoolmaster snapper (Lutjanus apodus; a species known to experience diel hyperoxia in mangrove creeks and coastal waters) with Transonic® flow probes and exposed them to an acute increase in temperature (at 1°Ch-1) in respirometers under normoxia and hyperoxia (150% air saturation), until their critical thermal maximum (CTmax). The CTmax of both groups was ∼39°C, and no differences in maximum cardiac function were recorded as the fish were warmed. However, temperature-induced factorial aerobic scope was significantly greater in fish tested under hyperoxia. These data suggest that hyperoxia will not protect coastal tropical fish species during marine heat waves, despite its effects on metabolic scope/capacity.

Early-life dispersal traits of coastal fishes: an extensive database combining observations and growth models

Abstract. Early-life stages play a key role in the dynamics of bipartite life cycle marine fish populations. Difficult to monitor, observations of these stages are often scattered in space and time. While Mediterranean coastlines have often been surveyed, no effort has been made to assemble historical observations. Here we build an exhaustive compilation of dispersal traits for coastal fish species, considering in situ observations and growth models (Di Stefano et al., 2023; https://doi.org/10.17882/91148). Our database contains over 110 000 entries collected from 1993 to 2021 in various subregions. All observations are harmonized to provide information on dates and geolocations of both spawning and settlement, along with pelagic larval durations. When applicable, missing data and associated confidence intervals are reconstructed from dynamic energy budget theory. Statistical analyses allow traits’ variability to be revisited and sampling biases to be revealed across taxa, space and time, hence providing recommendations for future studies and sampling. Comparison of observed and modelled entries provides suggestions to improve the feed of observations into models. Overall, this extensive database is a crucial step to investigate how marine fish populations respond to global changes across environmental gradients.

Ocean warming and novel species interactions boost growth and persistence of range‐extending tropical fishes but challenge that of sympatric temperate species in temperate waters

AbstractAimClimate change can have a broad range of impacts on the physiology and behaviour of animals. These effects can be mediated by the presence of other species in the community, but current forecasts of species responses to climate change largely ignore biological interactions. This is particularly true for novel interactions between range‐extending and native species, as this is often considered as noise and excluded from predictive models. Here we simulate how a tropical range‐extending and a local temperate fish species respond to the independent and combined effects of future ocean warming (RCPs 4.5 and 8.5) and novel ecological interactions in temperate ecosystems.LocationEast coast of Australia, along a ~ 2,000 km latitudinal gradient in a global climate warming hotspot.TaxonAbudefduf vaigiensis (tropical) and Atypicthys strigatus (temperate) fishes.MethodsWe use a dynamic energy budget model to simulate the length growth (i.e., increases in body length of individuals over time) and population persistence of juveniles of a tropical and a temperate fish species that form mixed‐species shoals, under different climate scenarios with and without the effects of novel ecological interactions.ResultsOur model forecasts that length growth of the juvenile tropical species will increase under ocean warming across subtropical to temperate regions. This increased length growth will be more drastic in temperate regions than in the subtropics, as winter warming will allow the tropical species to overwinter more frequently and show positive growth throughout the year. In contrast, warmer summer temperatures in the subtropics will likely exceed the optimal temperature of the juvenile temperate species at their trailing edge, resulting in reduced length growth under climate warming. Novel species interactions increased length growth of the juvenile tropical species but did not affect its winter or summer survival. In contrast, novel species interactions with tropical species were forecast to reduce length growth of the juvenile temperate species.Main ConclusionsOur study suggests that for some coastal fish species future warming will likely reverse body size dominance between temperate and tropical fish species, with increased novel interactions in temperate ecosystems (due to range extensions) but decreased novel interactions in the subtropics (due to range contractions). Novel species interactions and warming effects on body size and species survival are likely to reshuffle temperate fish communities and their competitive interactions.

Unraveling dispersal of a coastal fish species in the juvenile life stage in the Yellow Sea using otolith chemistry

Dispersal is a critical process in marine ecology, with profound implications for population conservation and fisheries management. Previous research has predominantly focused on reef-associated species, but studying the dispersal of more mobile fish species in nearshore environments is exceptionally challenging due to the complex coastal hydrography similar to reefs, and therefore dispersal knowledge of some coastal migratory behavior fish remains preliminary. In this study, we investigated the dispersal of a coastal fish species (small yellow croaker Larimichthys polyactis) in its juvenile life stage using otolith elemental fingerprints. We aimed to investigate the dispersal patterns of juveniles with otolith chemistry and identify potential natal sources. Results indicated that (1) significant geographical variations in the otolith elemental signatures can be considered as natural markers for assessing fish dispersal; (2) although small yellow croakers in the juvenile life stage are capable of settlement, a significant proportion of individuals continue subsequent passive dispersal; (3) juveniles may have originated from 2 natal sources in the sampling areas based on the differences in the near-core chemistry fingerprints. Results demonstrate the applicability of otolith chemistry fingerprints as natural tags in coastal waters and suggest that juveniles with the ability to settle will still employ dispersal strategies. This study contributes to research on fish dispersal in the early life stage and has significant implications for the marine fishery management of small yellow croaker.

Modeling environmental effects on fishery landings: A case study of whitemouth croaker (Micropogonias furnieri) in the Southwestern Atlantic shelf

Estuaries are very productive habitats that serve as spawning and nursery grounds for fisheries species. The Rio de la Plata (RdP) Estuary and its maritime front sustain valuable fisheries for Argentina and Uruguay. Micropogonias furnieri, the coastal fish species historically representing highest catches, has declined landings in recent decades. To enhance our understanding on how natural variability influences this resource and improves its management, we analysed the effect of environmental conditions on M. furnieri’s commercial landings in the long term using generalized linear and additive models (GLMs and GAMs). Explanatory variables, with up to a 10-year lag, included sea surface temperature, turbidity, salinity, wind, river runoff, and climatological indices: El Niño-Southern Oscillation (ENSO), the Southern Annular Mode (SAM) and the Southern Oscillation Index (SOI). Time-lagged analyses for single-covariate models reveal higher deviances explained (DE) at 2, 6, 7, and 8-year lags. Turbidity and salinity, followed by wind and temperature, are the most common variables affecting catches of M. furnieri for GLMs and GAMs. The absence of significant models with only climatological indices or river discharge indicates the impact of large-scale climate fluctuations and river runoff on the RdP Estuary conditions. The best-fitting GLM model includes SAM, turbidity, and wind (DE = 78.8%), whereas the GAM model includes turbidity and wind (DE = 86.4%). Sensitivity of M. furnieri’s catches to climatic signals (ENSO, SAM, SOI) is described for the first time. Our findings provide insights for authorities to implement management measures beyond fishing quotas encompassing environmental shifts in the long-term.

Fish assemblages in an environmentally complex narrow coastal region in the Southwestern Atlantic Ocean: an alternative nursery habitat for fishery species

The narrow coastal waters south of the Río de la Plata estuary are an oceanographically dynamic area where small-scale or artisanal fisheries occur. We analyzed 95 fishing bottom trawls from research surveys, along with oceanographic data collected during 2016 and 2017. Multivariate analyses (PERMANOVA, SIMPER, CAP) were applied to determine the spatial distribution of fish density, diversity and assemblage structure, as well as their relationship with the oceanographic environment. We estimated the length- frequency distribution of Sciaenid species to determine the presence of juveniles in the area. We recorded forty-three coastal fish species (15 commercial and 28 noncommercial) with the families Sciaenidae and Rajidae accounting for approximately ∼80% of the catches. Marine migrants were the most dominant in terms of species, followed by marine stragglers and estuarine residents. We detect differences in assemblages between surveys, primarily associated with nine species. Bottom salinity and temperature had a significant influence on the spatial structuring of discriminant species and functional groups. Sciaenid juveniles were found in areas with low salinities and shallow habitats, while adults were distributed in deeper and saltier waters. This work highlights the importance of physical conditions on fish assemblage dynamics in a complex environment, as well as the significant role of a narrow coastal band (∼5 km) as a nursery habitat for commercially important fish species.

Rapid climate change increases diversity and homogenizes composition of coastal fish at high latitudes.

Rapid warming at high latitudes triggers poleward shifts of species' distributions that impact marine biodiversity. In the open sea, the documented redistributions of fish lead to a borealization of Arctic fauna. A climate-driven borealization and increased species diversity at high latitudes are also expected in coastal fish communities, but they have not been previously documented on a large, biogeographic scale. Here, we investigate the impact of temperature change over the last 25 years on fish communities along the coast of Norway. The study area, spanning different ecoclimatic zones between 62° and 71° N, harbors over 200 species of boreal and Arctic fish. Several of these fish species are harvested by coastal and indigenous communities, influencing settlement geography and livelihood. The long-term data on coastal water temperatures and fish species were obtained from monitoring stations and scientific surveys. Water temperature measured at three fixed sampling stations distributed along the coast show increased temperatures during the study period. The fish species distribution and abundance data were obtained from the annually standardized scientific bottom trawl survey program. Fish species richness, which was highest in the south, increased with warming first in the south and then, gradually, further north, eventually affecting biodiversity in the whole study area. Fish community composition showed a distinct latitudinal pattern early in the study, with Arctic fish species confined to the north and boreal species dominating the south. The poleward shifts eventually eroded this zoogeographic pattern, resulting in more boreal fish species in the north and an increased homogenization of species composition along the Norwegian coast. The climate-driven reorganization of fish communities affects coastal ecosystems that are exposed to fisheries, aquaculture, and other rapidly expanding human activities, stressing the urgent need for a climate adaptation of integrated coastal management.

Potentially toxic trace elements in the muscle of coastal South American fish: Implications for human consumption and health risk assessment

Micropogonias furnieri and Urophycis brasiliensis are two coastal demersal fish species distributed in the southwestern Atlantic Ocean. Considering that many coastal areas in the southwestern Atlantic Ocean suffer from anthropogenic pressure, the aim of this study was to assess the level of potentially toxic trace elements (Ag, Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Se, Sr, V and Zn) in the muscle of coastal species, and evaluated the human health risk related to the consumption of muscle. Mercury, inorganic As (Asi), V, and Se showed a higher contribution to the total THQ. Considering two possible scenarios, Asi represents 1 % or 5 % of the total As, the total THQ was <1 for general population and of some health concerns for fishermen population (Total THQ > 1; 5 % Asi). Consequently these results show the importance of quantifying As species in muscle to generate more reliable risk estimates for human health.

Analysis of two coastal pelagic fish species (Sardinella aurita and Scomber colias) for early detection of the impact of anthropogenic metals released into the marine environment

In this study, the concentrations of several metals (Al, Cd,Cr, Cu, Fe, Pb, Zn) were analyzed in two species of fish (S. aurita and S. colias) in different years, including the period of the COVID-19 pandemic. The highest values of metals such as Al were found in the years 2019 8.661±0.434 mg/kg in S. colias and 6.487±1.485 mg/kg in S. aurita, and the year with the lowest concentration was 2020; 7.5±0.146 mg/kg in S. colias and 4.405±0.823 mg/kg in S. aurita, this pattern of concentrations occurs similarly for the other metals studied. Significant differences were found in the concentrations of these metals in both types of fish over the years. In general, metal concentrations were higher in 2019 and lower in 2020, coinciding with the period of reduced human activity during the pandemic. During the COVID-19 pandemic, reduced human activity led to a decrease in metal pollution in the marine environment, which had a positive impact on fish. However, it was noted that these effects may be temporary and may reverse when normal economic activities resume. These two fish species are sensitive indicators of metal pollution in the marine environment and it is important to take measures to reduce the release of contaminating metals into the environment. The need to adopt sustainable tourism practices and stricter environmental regulations to protect marine ecosystems is also mentioned.

Indirect costs of reproduction and the tradeoff between offspring size and number: a framework illustrated by fitness costs and benefits of ovarian fluid.

The theory describing the evolution of offspring size often assumes that the production cost per unit volume is the same for small and large offspring. However, this may not be true if indirect costs of reproduction (e.g., material and energetic costs of supporting offspring development) scale disproportionately with offspring size. Here we show how direct and indirect costs of reproduction can be explicitly modeled within the Smith-Fretwell framework and how observations of size-number relationships can thus be used to evaluate indirect costs. We applied this analysis to measures of egg volume and fecundity for over 300 individuals of a coastal fish species and found that the tradeoff was much stronger than the expected inverse (fecundity scaled with volume-1.843). Larger offspring were thus more expensive to produce. For our study species, an important indirect cost was that larger eggs were accompanied by disproportionately more ovarian fluid. Calorimetry and removal experiments were used to further measure both the energetic costs and fitness benefits of ovarian fluid. In addition, we show that indirect costs of reproduction can intensify size-number tradeoffs in a variety of fishes. Indirect costs of reproduction can be large and may therefore play an important role in the evolution of offspring size.

Depth and temperature preferences of meagre, Argyrosomus regius, as revealed by satellite telemetry.

Argyrosomus regius (commonly referred to as meagre), is one of Europe's largest coastal bony fish species and supports important recreational and commercial fisheries in the Atlantic and Mediterranean coasts. Demand for this species, and more recently for their swim bladders, has led to regional population declines and growing importance as an aquaculture species. Despite intense research in captivity, little is known about the spatial ecology of A. regius's wild population, including basic information such as vertical migrations and depth/temperature preferences. Previous research based on indirect data suggests a seasonal habitat shift from shallow to deeper waters, but this has never been validated through direct high-resolution movement data. In this study, we tagged 13 adult A. regius with pop-up satellite archival tags in the South of Portugal, which successfully returned data from 11 individuals including high-resolution data from six recovered tags (mean, range: 167 days, 28-301 days). We found that adults of this population spend 95.2% of their time between 5 and 75 m depth (mean ± SD, 30.9m ± 18.3m) and do not venture beyond 125 m. Across seasons, A. regius move across water temperatures between 13.3 and 24.8°C with a preferred thermal range between 14 and 18°C where they spent 75.4% of their time. The inferential modelling using this electronic data validated previous hypotheses by showing significant differences between a shallower and warmer summer habitat vs. a deeper and cooler winter habitat. Visual investigation of the diel effects on depth preferences suggests subtle changes in depth use between day and night during the warmer months of the year. We speculate that these patterns are in response to the species' behavioural ecology and physiology, reflecting the seasonal changes in water stratification and presence of prey, as well as on the species reproduction, which results in summer spawning aggregations in shallower areas.

Baited remote underwater video stations as a potential tool for assessing coastal rocky fishes in Chile

AbstractCoastal rocky fish species support important fishing activities, but basic information is lacking for many before catches decline. Monitoring and management of coastal rocky fish species is urgently needed in Chile, but knowledge of these species is fragmentary at best. Performance of Baited Remote Underwater Video Stations (BRUVS) for assessing rocky fish assemblages was evaluated in south‐central Chile. Seven medium‐ to large‐sized exploited species dominated fish assemblages in the survey area, including five small cryptic rocky reef fishes, one agnathan and a catshark species. These seven species represented 78% of the species targeted by commercial fishing in the survey area. Furthermore, this tool provided new information on behaviour of rocky fish species. The simple, inexpensive and light nature of single‐camera BRUVS may be crucial for maintaining monitoring programs along remote areas of Chile.

Age affects otolith shape in a coastal pelagic fish (Scomber colias Gmelin, 1789)

Otolith shape analysis is a common and efficient technique to study the population structure of fish species. This approach compares the overall otolith shape among individuals collected along the species´ distribution range. Otolith shape may change during ontogeny; thus, comparing otolith sample collections comprising multiple and variable age classes may lead to biased results. Therefore, it is crucial to test for possible effects of age on the otolith shape for a given species before interpreting potential differences in otolith collections. Here, we explored the effect of age on the otolith shape of a coastal pelagic fish species with a wide geographical distribution and fast growth rate, the Atlantic chub mackerel Scomber colias (Gmelin, 1789). This effect was tested across different years using different age assignment techniques (direct age reading and age back-calculation) and otolith shape descriptors (Elliptic Fourier and Discrete Wavelet). The results show that the age effect on otolith shape is most noticeable between age-1 and older fish, possibly due to rapid growth during the first year of life. Also, the age effect on otolith shape depended on the descriptor used, being more detected when using the Discrete Wavelet descriptor compared to Elliptic Fourier. Our results highlight the need to carefully examine age effects on otolith shape before conducting population structure analysis on mixed-age sample collections.

Assessment of human health hazard associated with heavy metal accumulation in popular freshwater, coastal and marine fishes from south-west region, Bangladesh

An analysis was conducted on both freshwater, coastal and marine fish species to evaluate the concentrations of heavy metals, with the aim of assessing their levels and examining the potential health risks for humans linked to the consumption of contaminated fish. This study estimate concentrations of Cr, Fe, Cu, As, Cd and Pb in 60 individuals belonging to 20 species (10 species for freshwater and another 10 for coastal and marine fishes) by using Atomic Absorption Spectrophotometer. Metal concentrations of Cr, Fe, and Pb in freshwater fishes and Cr, Fe, As, and Pb in marine fishes were exceeded the maximum allowable concentration (MAC). The Estimated Daily Intake (EDI), Average Pollution Load Index (APLI), Target Hazard Quotient (THQ), Hazard Index (HI) and Target Cancer Risk (TCR) of heavy metals were determined for the assessment of human health risk. Ranking order of the values of EDI for freshwater fishes, coastal and marine fishes were Cd > Fe > Pb > Cr > Cu > As and Cd > Fe > Pb > Cr > As > Cu. Highest APLI value of 8.14 (Puntius ticto) that is seriously polluted and 3.003 observed in Otolichthoides pama in freshwater and marine fishes, respectively. THQPb and THQAs for all the fish species were exceed the safe limit (THQ>1) suggesting potential health risk to consumers. The hazard index for both the fish samples were exceeded the USEPA (United States Environmental Protection Agency) permitted risk level (HI > 1). The target carcinogenic risk value for Cr and As were crossed the USEPA standard limit (TCR> 1E-04), which denotes that continuous consumption of studied fishes may cause health risk to the consumers. On the other hand, sensitivity analysis of freshwater, coastal and marine fishes indicates that all the metal concentrations were responsible factor for health risk.

Marine diets of anadromous Arctic char (Salvelinus alpinus) and pink salmon (Oncorhynchus gorbuscha) in Svalbard, Norway

During summer, native anadromous Arctic char (Salvelinus alpinus) and the alien species pink salmon (Oncorhynchus gorbuscha) now coexist in marine environments in Svalbard, following the introduction of the latter in the Barents Region. To investigate potential dietary competition between these two salmonid species, stomach contents from Arctic char (n = 301) and pink salmon (n = 28) were sampled from different areas within the archipelago. The most important prey in terms of biomass for both salmonid species were amphipods; Themisto libellula (B = 26.0%) for Arctic char and Onisimus litoralis (B = 35.0%) for pink salmon. Pianka’s niche overlap revealed that dietary overlap between the two species was moderately high (Oobs = 0.59); both species had strong associations with intertidal invertebrates in areas where direct comparisons were possible (Kongsfjorden/Krossfjorden). However, both salmonid species did also eat some fish, with Arctic char consuming more offshore pelagic fish, while the small number of fish eaten by pink salmon were primarily coastal demersal fish species. Arctic char was a more generalist feeder, while pink salmon was more of a dietary specialist. Furthermore, the diet composition of the Arctic char consisted of 32.9% Atlantic prey while the pink salmon, surprisingly, ate only Arctic species, likely due to their tightly coastal feeding habits. Even though the sample size for pink salmon was low, this study contributes new insights into salmonid diets in Svalbard and the potential for introduced species to compete with native Arctic endemics, particularly in the expected warmer Arctic of the future.

Residency, home range and inter-annual fidelity of three coastal fish species in a Mediterranean coastal lagoon

In the Gulf of Lion (NW Mediterranean), fish species such as gilthead sea bream Sparus aurata, European seabass Dicentrarchus labrax, and salema Sarpa salpa show seasonal occupation of coastal lagoons, presumably as feeding grounds during their adult life stage. The role of the lagoons in these species' life cycles remains unknown, particularly with respect to their residency, space-use, and inter-annual fidelity. Using acoustic telemetry, the movements of 72 seabream, 58 seabass, and 81 salema were monitored over four years within Prévost Lagoon (Hérault Department, Occitania Region), to characterize (1) the main seasonal patterns of space use inside the lagoon and (2) their annual migrations between the lagoon and the sea. Overall, all three species were highly resident in the lagoon during the spring/summer foraging season; seabass was the only species that also displayed high residency to the lagoon throughout the winter breeding season. The three species showed differences in their space use, although they all mainly inhabited the deep lagoon centre and adjacent shellfish farms, with very small individual home ranges (mean ± SD, 0.12 ± 0.06 km2 over all species). All species showed some inter-annual fidelity to the lagoon (>43% at minimum for seabream) although these fidelity rates were probably underestimated due to fishing mortality, which is probably high during the winter breeding season. Overall, this study reveals that coastal lagoons are key foraging habitats for these species in the Gulf of Lion. The high residency and inter-annual fidelity suggest that any increase of anthropogenic pressure within the lagoon could negatively impact these fish populations. Therefore, protection of such productive habitats could be beneficial for long-term management of emblematic coastal species and the fisheries that they support.

Mesopelagic fishes are important prey for a diversity of predators

Through daily vertical movements, mesopelagic fishes contribute to global carbon export and, when eaten, link primary consumers to higher trophic level predators. Although the importance of mesopelagic fishes as prey to individual predator species has been explored, a comprehensive assessment of mesopelagic fishes as prey at the scale of a large marine ecosystem would advance our observing, modeling, and predicting of biodiversity and ecosystem function. We use diet samples from over 105,000 individual predators from 143 taxa in the California Current Ecosystem (CCE) to quantify and evaluate the role of mesopelagic fishes as prey. For 11 predator taxa, including protected mammal species, pelagic squids, a shelf-edge-associated rockfish and highly migratory species, mesopelagic fishes occurred in greater than 25% of all diet samples, likely comprising an important source of prey. Of the 143 taxa represented, individuals from 36 taxa, or 25% percent of all predator taxa in the database, consumed at least one mesopelagic fish species, including economically important fishery species such as Bluefin tuna (16% of all non-empty diet samples), Albacore (19%), Swordfish (50%), Humboldt squid (52%), and Pacific hake (4%). Compared with coastal pelagic fish species (essential prey in the CCE), mesopelagic fish were more frequently encountered in the diets of 21 predator taxa. Lanternfish (family Myctophidae) were the most common prey and consumed by the greatest diversity of predators (32 taxa), but an additional 16 families of mesopelagic fishes were also consumed by predators, highlighting the diversity of organisms inhabiting mesopelagic depths. Mesopelagic fishes were found in the diets of predators collected from shelf depths to well offshore, accentuating the role of mesopelagic fishes as prey across habitats, especially for predators foraging over the slope and further offshore. Our work illuminates the importance of mesopelagic fishes as prey to a diversity of economically valuable and protected species, underscoring the need to incorporate mesopelagic fishes more comprehensively into food web models, global carbon budgets and ultimately our understanding of ecosystem function.

Contrasting intra-individual variation in size-based trophic and habitat shifts for two coastal Arctic fish species

Within and among species variation in trophic and habitat shifts with body size can indicate the potential adaptive capacity of species to ecosystem change. In Arctic coastal ecosystems, which experience dramatic seasonal shifts and are undergoing rapid change, quantifying the trophic flexibility of coastal fishes with different migratory tactics has received limited attention. We examined the relationships among body length and condition (Fulton’s K, phase angle from Bioelectrical Impedance Analysis) with trophic and habitat shifts (differences in δ15N and δ13C between blood tissues with different turnover rates) of two abundant and culturally important species, anadromous Arctic char (Salvelinus alpinus, n = 38) and sedentary Greenland cod (Gadus ogac, n = 65) during summer in coastal marine waters near Ulukhaktok, Northwest Territories, Canada. Habitat shifts (δ13C) increased with length (i.e., pelagic to benthic-littoral) and crossed-equilibrium (zero) at mid-sizes for both species. Seasonal trophic shifts (δ15N) were generally positive (i.e., increasing trophic level) for Arctic char and negative for Greenland cod. As hypothesised, intra-individual variation in size-based trophic shifts (δ15N-length residuals) increased with length for Arctic char. However, there were no trends with length in Greenland cod. Our findings highlight the importance of flexibility through ontogeny and mobility for Arctic char, whereas Greenland cod were generalist to localized prey and habitat across all sizes. The significant effect of body condition (phase angle) on size-based trophic shifts in Arctic char, and size-based habitat shifts in Greenland cod, highlight the potential trade-offs of contrasting life history strategies and capacity for ontogenetic niche plasticity.

Exploring microplastic contamination in reef-associated fishes of the Tropical Atlantic

Microplastics (MPs) are ubiquitous in marine compartments, and their transboundary distribution favours the dispersion and accumulation of particles in ecosystems. This study investigated MP contamination in four coastal fish species (Haemulon squamipinna, Chaetodon ocellatus, Syacium micrurum, and Alphestes afer) from the southwestern Tropical Atlantic. An alkaline treatment was applied to extract MPs from the digestive tracts, and a Laser Direct Infrared (LDIR) system was used to identify polymers. All species analysed were contaminated with MPs, with Alphestes afer being the most contaminated (1.45 ± 1.09 MPs individual−1; frequency of occurrence 80 %). No significant differences were found in the number and size of detected particles among species. The most common shapes were fibres and films, and polyethylene was the most abundant polymer. This study provides important baseline data on MP contamination in coastal fish species inhabiting complex habitat areas relevant for conserving marine biodiversity.

Coastal Fish Fauna in the Cystoseira s.l. Algal Belts: Experiences from the Northern Adriatic Sea

Cystoseira s.l. forests are recognised as important habitats which host diverse coastal fish assemblages. Many fish species use such habitats as feeding, breeding, and nursery grounds. Since the coastal fish community depends on the availability of dense macroalgal belts, the decline of these habitats in the Mediterranean Sea also affects the density of coastal fish species. We studied the coastal fish assemblage in Cystoseira s.l. forests in three consecutive years 2019–2021 in the Gulf of Trieste (Adriatic Sea). Data on coastal fish fauna were collected by visual counts conducted by SCUBA diving. Data on algal cover and habitat types were obtained by recording with a video camera. Similarities and differences in the fish community were analysed in terms of habitat and substrate preferences. A total of 34 species were recorded in Cystoseira forests. The results of the present study show that the different algal cover and associated depth gradient have different effects on the fish assemblage in coastal waters, affecting species composition and abundance. For many species, particularly labrids and sea breams, there is a decreasing temporal trend in frequency of occurrence and density. However, fish community trends can be used as a good “proxy” to evaluate the algal belt status. Our results indicate that rapid conservation and restoration actions are needed to stem the decline of Cystoseira s.l. forests.