Coastal Fish Research Articles

A Machine Vision Approach for Recognizing Coastal Fish

Coastal fish is one of the prominent marine resources, which takes a necessary role in the economic growth of a country. Because of environmental issues along with other reasons, not only most of the marine resources are diminishing but also many coastal fishes are getting extinct gradually. As a result, the young peoples have insufficient knowledge of coastal fish. This issue can be solved with the use of vision-based technologies. To deal with this situation, a coastal fish recognition system based on machine vision is conceived, which can be approached by the images of coastal fish that are captured with a portable device and identify the fish to recognize fish. Numerous experimental analyses are executed to exhibit the benefit of this proposed expert system. In the beginning, conversion of a color image into a gray-scale image occurs and the gray-scale histogram is developed. Using the histogram-based method, image segmentation is conducted. After that, a set of thirteen features comprising of four classes is extracted to be fed to a classifier. For reducing the number of features, PCA is applied. To recognize coastal fish, three cutting-edge classifiers are performed, where k-NN provides a potential accuracy of up to 98.7%.

<i>Limnotrachelobdella okae</i> (Hirudinida: Piscicolidae) Parasitic on Big-scaled Redfin, <i>Pseudaspius hakonensis</i> (Cypriniformes: Leuciscidae), in Two Brackish Water Lakes, Hokkaido, Japan

Specimens of the coastal marine fish leech Limnotrachelobdella okae (Moore, 1924) were collected from the pelvic fins and lateral body surface of big-scaled redfin, Pseudaspius hakonensis (Günther, 1877), in two brackish water lakes, Lake Tofutsu and Lake Abashiri, on the Sea of Okhotsk coast, Hokkaido, northern Japan. The external morphology of the specimens is briefly described, and the two lakes represent new locality records for the leech. Similarly to coastal marine waters, inshore brackish water lakes are suggested to be a habitat in which L. okae can complete its life cycle. Seasonal occurrence of the species may differ between subarctic Hokkaido and three temperate regions of Japan (Honshu, Shikoku, and Kyushu). The role of big-scaled redfin and its congener, Pacific redfin, Pseudaspius brandtii (Dybowski, 1872), in transporting L. okae alive from the coastal sea to brackish and fresh water bodies is discussed in terms of their diadromous migration ecology.

Insights into the spatio‐temporal variability of spawning in a territorial coastal fish by combining observations, modelling and literature review

AbstractIn bipartite life cycle fishes, spawning represents the onset of propagules dispersal, with eggs and larvae experiencing anisotropic transport and high mortality rates, before eventually metamorphosing and settling. Hence, early‐life stages operate as bottlenecks for population demography by strongly constraining recruitment. Despite its significance, spawning is rarely explicitly considered in ecosystem management due to a lack of knowledge, for many species, about where and when spawning occurs. Previous evidences suggest that temperature is among the main drivers of spawning in Teleosts. Using the ecologically and economically relevant white seabream Diplodus sargus in the central Mediterranean Sea as a case study, we assess the abiotic factors that regulate the onset and duration of spawning and subsequent dispersal. Lagrangian backtracking simulations fed with early‐life observations allow locating 11 spawning events, which are then associated to simulated temperatures ranging from 14.8° C to 20.6° C, in close agreement with previous estimates. Based on this range of suitable temperatures, we model the spatio‐temporal variability of spawning success at broad‐scale over 10 years (2005–2014) following the backtracking approach with hypothetical constant settlement areas. It highlights a prominent inter‐annual variability in the Adriatic and Siculo‐Tunisian strait driven by oceanographic processes. Moreover, a powerful clustering method uncovers relatively stable spawning areas in the Ligurian and Tyrrhenian seas with both early (January to Mid‐February) and late (April to June) spawning peaks. Our methodology can be applied to other species and oceanic systems to investigate how oceanic processes impact spawning success, enabling the design of sound management strategies.

Side-Scan Sonar Coupled with Scuba Diving Observation for Enhanced Monitoring of Benthic Artificial Reefs along the Coast of Terengganu, Peninsular Malaysia

Since the 1970s, artificial reef (AR) deployment has been one of the common approaches to augment the local production of coastal fish in Malaysia. However, there is a lack of strategy to assess and evaluate the success of pre-deployed AR. Realizing the need for an effective qualitative and quantitative monitoring and evaluation of AR, this study proposes side-scan sonar coupled with scuba diving observation for the enhanced monitoring of pre-deployed Bioceramic Korean (BK) AR along the coast of Terengganu, Peninsular Malaysia. This method employs an integrated side-scan sonar with a data acquisition system for the detection of the precise location of the BK AR which were deployed at Tukun Telaga Batin off the Terengganu coastline in 2003 by the Fisheries Development Authority of Malaysia (FDAM). Following the determination of the exact location of three BK AR areas, a scuba diving team was sent to survey the physical conditions of the AR and assess the feasibility of the AR as an artificial habitat for marine life. The scan sonar images were compared with the captured photographs and videos acquired during the scuba diving session for a comprehensive value-added assessment. The collected data from the scuba diving session were also processed to measure the fish diversity, the fish biomass, and identify the fish community surrounding the AR. Based on the results, the BK AR remained in extremely good condition, physically intact, without significant breakage or damage, and with no major subsidence into the sediment after 19 years of deployment. A total of 108 BK AR modules were detected in three large groups using the mosaicked sonar images. Following cross-examination to validate the AR measurements using the AR’s shadows on the seafloor, the height of the BK AR consistently ranged from 1.7 m to 1.8 m. In addition, 34 species of fish from 14 families and 26 genera were identified, with most species classified as reef-associated (RA) fish with a biomass value of 1173.31 ± 1136.69 kg m−3, indicating the successfulness of the BK AR as fish-aggregating devices (FADs). The growth of hard corals on top of the bioceramic plate of the AR module further supported the diversified community of marine life surrounding the BK AR. In conclusion, the side-scan sonar coupled with scuba diving observation demonstrates an effective qualitative and quantitative technique for the monitoring and evaluation of pre-deployed AR. This strategy is recommended to be utilized to determine the success of pre-deployment AR.

Combining of C, N and specific Hg stable isotopes to track bioaccumulation of monomethylmercury in coastal and freshwater seafood

Human exposure to monomethylmercury (MMHg) through seafood consumption is a global concern. This study investigates the potential sources and processes of MMHg in seafood of coastal and freshwater areas through combing of δ13C, δ15N, and specific Hg (including MMHg and inorganic Hg (IHg)) isotopes. The results showed that δ13C and δ15N values exhibit different patterns in coastal and freshwater species. Δ199HgMMHg/δ202HgMMHg values suggested that coastal and freshwater seafood undergo similar aqueous MMHg photodegradation processes. The Δ199HgMMHg values could distinguish that, coastal fish absorb MMHg from water column whereas coastal shellfish absorb MMHg mainly from sediment. The positive values of Δ199HgIHg in seafood could reflect in vivo MMHg demethylation and IHg reabsorption. Positive correlation between δ15N and Δ199HgIHg indicated that aquatic organisms in various trophic levels may have different MMHg demethylation efficiency. We proposed that combining of multiple isotopes can provide overall profiles on aquatic MMHg biogeochemical cycle and bioaccumulation.

Diversity and Assemblage of Harmful Algae in Homestead Fish Ponds in a Tropical Coastal Area.

Simple SummaryHarmful algae are those which release toxins to the aquatic ecosystems. Excessive growth of these algae can kill fish, create anoxia, impede aquaculture activities and contaminate aquatic food. Therefore, it is important to investigate their occurrence, diversity and abundance in pond aquaculture systems. In this study, we have identified 81 genera of harmful algae from 30 coastal homestead ponds mainly consisting of Microcystis spp. (30.14%) and Actinoptycus spp. (18.32%). Based on taxonomic classes, the community assemblage was dominated by Cyanophyceae, Chlorophyceae and Bacillariophyceae. Statistical analyses demonstrated that that dissolved oxygen, nitrates, phosphates, sulphates, salinity and transparency influence the abundance of identified algal genera.Algae are the naturally produced food for fish in any aquatic ecosystem and an indicator of a productive pond. However, excess abundance of harmful algae can have detrimental effects on fish health. In this study, the algal communities of 30 coastal homestead fish ponds were investigated to identify the diversity, assemblage and controlling environmental variables of harmful algae from a tropical coastal area. The findings showed that 81 of the 89 genera of identified algae were harmful, with the majority of them being in the classes of Cyanophyceae (50.81%), Chlorophyceae (23.75%), Bacillariophyceae (9.5%), and Euglenophyceae (8.47%). Microcystis spp. alone contributed 28.24% to the total abundance of harmful algae. Significant differences (p < 0.05) in algal abundance were found among the ponds with the highest abundance (470 ± 141.74 × 103 cells L−1) at pond (S25) near agricultural fields and the lowest abundance (109.33 ± 46.91 × 103 cells L−1) at pond (S14) which was lacking sufficient sunlight and nutrients. Diversity indices, e.g., dominance (D), evenness (J′), richness (d) and Shannon diversity index (H′) ranged from 0.17 to 0.44, 0.23 to 0.6, 0.35 to 2.23 and 0.7 to 1.79, respectively, indicating a moderate range of diversity and community stability. Community composition analysis showed the assemblage was dominated by Cyanophyceae, Chlorophyceae and Bacillariophyceae, whereas, multivariate cluster analyses (CA) identified 11 major clusters. To identify the factors controlling their distribution or community assemblages, eight environmental variables (temperature, pH, dissolved oxygen (DO), salinity, transparency, nitrates, phosphates and sulphate) were measured. ANOVA analysis showed that the variables significantly differed (p < 0.05) among the ponds, and canonical correspondence analysis (CCA) demonstrated that DO, nitrates, phosphates, sulphates, salinity and transparency have the most impact on the abundance of algal genera. In addition, analyses with Pearson’s correlation coefficient showed that the abundance of total algae, diversity and community were mainly governed by phosphates and sulphates. These results can be used to identify and control these toxic algal groups in the local aquaculture sector.

Evaluating Food Security Challenges during the Covid-19 Pandemic in Nigeria’s Coastal Fishing Communities

This descriptive qualitative study examined how food security was undermined during the covid-19 pandemic in some coastal fishing communities in Nigeria. The study used the Household Economic Approach as a theoretical basis to explain the challenges of food security in coastal communities based on evidence from the Covid-19 pandemic. Data were generated from open-ended interviews conducted with 30 participants in three coastal fishing communities in Akwa Ibom state, Nigeria. The study also relied on secondary data from books, reports, and journal articles. From the analysis, results showed that the various preventive measures adopted to curb the spread of the virus posed a challenge to fish production, access, and consumption. Furthermore, the findings revealed that in addition to other human security issues, covid-19 was a natural mechanism whose emergence only exacerbated existing food insecurity in coastal fishing communities. Based on the ongoing, the study concludes that, food security can be enhanced in coastal fishing communities through cross-sectorial partnerships and collaborations between the government, civil society groups and the blue economy.&#x0D; &#x0D; &#x0D; Received: 11 July 2022 / Accepted: 29 August 2022 / Published: 2 September 2022

Are social conditions important to increase household income? The case of coastal fishers in Makassar City, Indonesia

Social conditions strongly influence changes in household income because they play a critical role in improving the household welfare of coastal fishing communities. The purpose of the study is to analyze the influence of social conditions on the growth of fisherman's household income in Makassar City, Indonesia. Quantitative research method using survey instrument was addressed to 46 fishers' households by applying the purposive sampling technique. The analytical method used was multiple regression with the exponential function model. This study found that social factors such as the age of the head of the family and the number of working family members contributed to changes in the increase in household income because they had a significant positive effect. On the other hand, the number of dependent household members did not contribute anything because it had a negative effect on changes in the income level of fishers' households. Likewise, the wife's level of formal education did not affect the household income. Related to social factors as a determinant of improving the fishers' household economy, efforts to increase it can be made through on-fishing and off-fishing. On-fishing is carried out with the support of a gross tonnage boat. Household members do off-fishing in postharvest handling, handling, processing, and marketing marine products.JEL Classification D10; Q22; Z10

The speciation of arsenic in the muscle tissue of inland and coastal freshwater fish from a remote boreal region

Elevated concentrations of total arsenic (As) have been reported in boreal freshwater fish in both human-impacted and relatively pristine areas. We assessed the arsenic speciation profiles in muscle tissue of six fish species (n = 300) sampled from nine locations across a remote freshwater watershed in northern Ontario, Canada, extending from inland headwater lakes to the coastal marine confluence. Of the five arsenic species measured, only arsenobetaine (AsB) and dimethylarsinic acid (DMA) were detected in these fish. Riverine fish had up to 10-fold higher total [As] when compared to lacustrine fish. On average, these riverine fish also had higher percentages of AsB (%AsB, 60 ± 26%) and lower percentages of unmeasured arsenic (%UNM, 20 ± 21%), compared to lacustrine fish (28 ± 18% and 52 ± 21% %AsB and %UNM, respectively). DMA percentages (%DMA) were relatively consistent across the watershed, averaging 20 ± 21% across all fish. We examined ecological drivers of As speciation and found that %AsB increased slightly with fish weight in large-body predatory fish, but not in forage fish or insectivores. Furthermore, %AsB was positively related to trophic elevation (inferred from δ15N) in lacustrine fish across 3 out of 4 communities and within some populations. Lastly, riverine fish with a more marine-based diet had markedly higher %AsB when compared to fish with more freshwater-based diets, indicating an effect of anadromy on arsenic speciation. Overall, knowledge on arsenic speciation in freshwater fish has been limited and these results indicate potential drivers that can be considered in future studies. Furthermore, the absence of toxic inorganic As species in these boreal fish is an important consideration for future environmental monitoring practices and risk assessments, some of which assume 10–20% of total [As] in fish is present as toxic inorganic As. Additional studies on As bioaccumulation and biotransformation are needed in freshwater systems, particularly at the base of aquatic food webs.

An Insight into the Feeding Ecology of Serranus scriba, a Shallow Water Mesopredator in the Northern Adriatic Sea, with a Non-Destructive Method

Serranus scriba is a common member of the coastal fish community in the Adriatic Sea, but knowledge about its feeding ecology is scarce. The aim of this paper is to present new evidence about its food preferences and feeding habits. An innovative non-destructive method of fecal pellet analysis was used for this study. This method does not require sacrificing specimens and the fish can be released back into the sea alive after the laboratory work. The results demonstrated that S. scriba mainly preys on decapods, followed by polychaetes, isopods, fish, mollusks and swarming shrimps. The calculated index of trophic diversity (ITD) value of 0.89 indicates that it is an opportunistic feeder that feeds on a wide range of different prey. According to the calculated trophic level of 3.43, which is higher than that of other members of the community, S. scriba is also an important piscivorous predator. With age, S. scriba undergoes an ontogenetic shift. The proportion of crustaceans, gastropods and polychaetes decreases with age and body size, while the proportion of fish increases.

Genetics Reveal Long-Distance Virus Transmission Links in Pacific Salmon.

Simple SummaryThe transmission of viruses between host populations is essential for viruses to persist on the landscape. Therefore, the identification of specific transmission links can provide insights into how a virus moves from source to recipient (sink) populations, allowing for the development of strategies to interrupt transmission routes and control viral disease. For the fish pathogen infectious hematopoietic necrosis virus (IHNV), this study identifies three transmission links associated with the emergence of IHNV in coastal Washington steelhead trout populations between 2007 and 2011. The links were identified by the genetic typing of virus isolates obtained from coastal fish and potential source fish from the Columbia River Basin. Three exact genotype matches were found, indicating at least three introductions of virus from Columbia fish to coastal fish during years of the emergence event. Likely sources were juvenile fish in the Columbia region experiencing disease, and the first detected recipient populations in all cases were adult fish returning to coastal hatcheries. Variation in timing and distance for these three transmission links will provide Pacific Northwest fish health managers with a better understanding of IHNV transmission routes from Columbia region fish to coastal steelhead trout.In the coastal region of Washington State, a major pathogen emergence event occurred between 2007 and 2011 in which steelhead trout (Oncorhynchus mykiss) experienced a high incidence of infection and disease outbreaks due to the rhabdovirus infectious hematopoietic necrosis virus (IHNV). Genetic typing showed that the introduced viruses were in the steelhead-specific MD subgroup of IHNV and indicated the most likely source was a virus from the nearby Columbia River Basin. In the current study, full-length viral glycoprotein (G) gene sequences were determined for 55 IHNV isolates from both coastal and Columbia fish populations to identify specific source populations and infer mechanisms of transmission to coastal steelhead. We identified three transmission links based on exact fullG genotype matches between Columbia and coastal fish. In all cases, the likely source population was infected juvenile fish, and sink populations were adult fish returning to coastal rivers to spawn. The time intervals between detection in source and sink populations varied from 6 months to nearly 4 years, suggesting different transmission pathways. Surprisingly, distances between source and sink populations varied between 140 and 1000 km. These results confirm repeated introductions of virus from Columbia River Basin fish as the cause of emergence of MD virus on the Washington coast from 2007 to 2011.

Social-ecological vulnerability of fishing communities to climate change: A U.S. West Coast case study.

Climate change is already impacting coastal communities, and ongoing and future shifts in fisheries species productivity from climate change have implications for the livelihoods and cultures of coastal communities. Harvested marine species in the California Current Large Marine Ecosystem support U.S. West Coast communities economically, socially, and culturally. Ecological vulnerability assessments exist for individual species in the California Current but ecological and human vulnerability are linked and vulnerability is expected to vary by community. Here, we present automatable, reproducible methods for assessing the vulnerability of U.S. West Coast fishing dependent communities to climate change within a social-ecological vulnerability framework. We first assessed the ecological risk of marine resources, on which fishing communities rely, to 50 years of climate change projections. We then combined this with the adaptive capacity of fishing communities, based on social indicators, to assess the potential ability of communities to cope with future changes. Specific communities (particularly in Washington state) were determined to be at risk to climate change mainly due to economic reliance on at risk marine fisheries species, like salmon, hake, or sea urchins. But, due to higher social adaptive capacity, these communities were often not found to be the most vulnerable overall. Conversely, certain communities that were not the most at risk, ecologically and economically, ranked in the category of highly vulnerable communities due to low adaptive capacity based on social indicators (particularly in Southern California). Certain communities were both ecologically at risk due to catch composition and socially vulnerable (low adaptive capacity) leading to the highest tier of vulnerability. The integration of climatic, ecological, economic, and societal data reveals that factors underlying vulnerability are variable across fishing communities on the U.S West Coast, and suggests the need to develop a variety of well-aligned strategies to adapt to the ecological impacts of climate change.

Application of environmental DNA as a tool for detecting intertidal habitat use by forage fish

Many coastal forage fish species spend most of their life history using the water column, but some species such as Pacific Sand Lance (Ammodytes personatus) and Surf Smelt (Hypomesus pretiosus) have a requirement for intertidal sediments for spawning and or burying. Detection of suitable but typically uncommon intertidal habitats for spawning has historically relied on extensive visual surveys for eggs from large sand samples. In the present study, we developed and validated two new non-destructive qPCR-based tools for detecting Sand Lance and Surf Smelt eDNA from small sand samples. A total of 279 composite transect sand samples were collected from 101 beaches and were tested for eDNA sample integrity using the IntegritE-DNATM test. Initial testing showed that all but 42 of 46 samples passed after an inhibitor clean-up step. Of the 101 beaches sampled 275 times, there were 111 detections of Sand Lance on 52 beaches, and there were 13 detections of Surf Smelt on 10 beaches. One hundred and eighty-one samples were paired with visual egg counts and 76 (42%) of these tested positive for Sand Lance while 9 of 132 (7%) samples tested positive for Surf Smelt. For the 27 paired samples with two or more Sand Lance eggs visually detected there was a significant positive correlation (r = 0.694, p = 0.0001) with eDNA copies per liter suggesting that a larger Sand Lance presence is easily and reliably detected using eDNA. The methods and approaches described herein will serve as a foundation for broad application of eDNA approaches for forage fish species that utilize intertidal benthic habitats.

Multivalvulidan myxosporeans from marine fishes in Nha Trang Bay, Vietnam, with descriptions of Kudoa igori n. sp. and Kudoa borimiri n. sp. from mullets.

In March and April 2018, we carried out a survey of myxosporean parasites in coastal fishes collected from Nha Trang Bay in Vietnam's East Sea. Of the 159 fish specimens, 18 fish species were represented, belonging to 10 families. In 8 host species, 7 myxosporean species were found, representing the genera Kudoa and Unicapsula. Two of these species were new to science: Kudoa igori n. sp. from the gallbladder of Longarm mullet Osteomugil cunnesius (Valenciennes, 1836) (prevalence 10%) and Kudoa borimiri n. sp. from skeletal muscles of Longarm mullet and Longfinned mullet Osteomugil perusii (Valenciennes, 1836) (prevalence 30% and 60%, respectively). Vegetative stages were not found. Spores of K. igori n. sp. were small, orbicular to quadrate in apical view, and with four equal valves. In lateral view, spores were shallowly ovoid with a slightly protruding anterior pole. The 4 polar capsules were slightly unequal sizes and were oriented toward the apex of the spore. Dimensions were as follows: spore length 4.56 ± 0.22 (4.18-4.56), thickness 4.42 ± 0.39 (3.55-5.13), width 5.74 ± 0.46 (4.66-6.50), length of biggest polar capsule 1.38 ± 0.14 (1.1-1.65), middle 1.28 ± 0.12 (1.03-1.53), smallest 1.13 ± 0.11 (0.94-1.30), width of biggest polar capsule 1.03 ± 0.14 (0.83-1.4), middle 0.92 ± 0.12 (0.76-1.08), smallest 0.74 ± 0.12 (0.55-0.94). Spores of K. borimiri n. sp. had four equal valves with slightly rounded ends and were quadrate in apical view. In lateral view, spores were broadly deltoid. Four equal-sized polar capsules opened at the apex of the spore. In O. cunnesius, spore dimensions were as follows: length 3.51 ± 0.15 (3.34-3.92), thickness 3.65 ± 0.38 (2.79-4.21), width 4.97 ± 0.37 (4.13-5.97), length of the polar capsules 1.23 ± 0.18 (0.99-1.57), width 0.88 ± 0.07 (0.70-1.00). Overlapping dimensions for K. borimiri n. sp. spores were also found in O. perusii. Other known myxozoan species we encountered were Kudoa thyrsites and Kudoa whippsi, which had not previously been reported from the East Sea and Vietnam. We also encountered Kudoa monodactyli, which had not previously been reported from Nha Trang Bay. In addition, we report 2 additional species, a Kudoa sp. and a Unicapsula sp., that were not attributable to previously described myxozoans and need further investigation to completely characterize.

Studying the tidal-induced water circulation pattern within EL-Burullus fishing harbor, Egypt, using CMS-PTM numerical modeling

Protection from waves and providing an appropriate calmness ratio are vital requirements in the designing phase of a harbor. Another crucial issue is guaranteeing sufficient water circulation as a key indicator for water quality and avoiding the associated environmental problems of poor water quality conditions. In a coastal harbor, the interior basin's water quality largely depends on the harbor's natural/self-ability to flush out different existing pollutants. El-Burullus fishing harbors is one of the Egyptian coastal fishing harbors that suffer from environmental issues such as accumulated pollutants, particularly in stagnant areas, and deterioration of water quality within the harbor's basin. Investigating water quality status within the coastal harbors necessitates knowledge about the mechanism of water circulation patterns within the harbor. The most common indicator for the water renewal and circulation pattern evaluation is the flushing time. Therefore, a coupled coastal hydrodynamic modeling system and particle tracking model (CMS-PTM) are utilized to investigate the tidal-induced circulation pattern within the El-Burullus fishing harbor, considering two tide scenarios (best and worst). Three locations (where most operational fishing facilities exist) were selected as point sources (instantaneous mass) for particle release. The results highlight the role of tidal actions on the water circulation within El-Burullus harbor and how the residence time varies based on the source release location.

Inventory of the fauna and flora of the Northeast new ecosystem of Bizerte lagoon (Tunisia), Southeastern Mediterranean sea

Bizerte lagoon is a valuable socio-economic ecosystem which is renowned for its significant biodiversity and its strategic position in the Mediterranean and in northern Tunisia. It is characterized by an important biodiversity and a high biological productivity, which makes of it a nursery for several marine species. It is also a place of brood stock maturation for others and a feeding area for many migratory species. Its shores and maritime space host lots of human activities, such as coastal fishing, shellfish farming, maritime traffic, recreational fishing and nautical sports, besides 277 industries spanning several sectors of activity such as leather and textile as well as the refining of hydrocarbons and the steel industry. These activities cause severe pollution and result in many anthropogenic disturbances. The aim of this work is to study the sanitary state of Bizerte Lagoon using a biological and ecosystem approach that exploits bio-ecological indicators at the scale of specimen, population, community or whole ecosystem. The findings of this study have revealed the following facts: the peri-lagoon part of the Northeast zone is distinguished by an interesting biological diversity. According to statistical descriptors, the most abundant and frequent zoological groups are gastropod mollusks followed by crustaceans. In terms of diversity indexes, the values obtained showed that the Northeast zone has a poor to mediocre ecological status. This research demonstrates that Bizerte Lagoon is undergoing an anthropic pressure that has been jeopardizing the biodiversity of this ecosystem.

Assessing the Spatiotemporal Relationship between Coastal Habitats and Fish Assemblages at Two Neotropical Estuaries of the Mexican Pacific

Differences in fish assemblages’ structures and their relations with environmental variables (due to the variations in sampled seasons, habitats, and zones) were analyzed in two adjacent estuaries on the north Pacific coast of Mexico. Environmental variables and fish catches were registered monthly between August 2018 and October 2020. Multivariate analyses were conducted to define habitats and zones based on their environmental characteristics, and the effect of this variability on fish assemblages’ composition, biomass, and diversity (α and β) was evaluated. A total of 12,008 fish individuals of 143 species were collected using different fishing nets. Multivariate analyses indicated that fish assemblages’ structures were different between zones due to the presence, height, and coverage of distinct mangrove species. Additionally, depth and salinity showed effects on fish assemblages’ diversity (α and β-nestedness), which presented higher values in the ocean and remained similar in the rest of the analyzed zones and habitats. These results and the differences in species replacement (β-turnover) indicate the singularity of fish assemblages at estuaries (even in areas close to the ocean) and the necessity to establish local management strategies for these ecosystems.

Life‐history traits and temporal patterns in the incidence of coastal fishes experiencing tropicalization

AbstractClimate change is causing shifts in the geographic distributions of coastal fish species toward higher latitudes. However, local fish communities found in higher latitudes today are not simply those found in lower latitudes in the past because the sensitivity of species to various environmental conditions is different. Responses of fish to environmental conditions differ depending on their life‐history traits such as the maximum population growth rate, age of maturity, and generation time because these traits are constrained by environmental conditions. Here, we investigate associations among temporal patterns in presence–absence (incidence) data, life‐history traits of species, and environmental conditions to elucidate the potential mechanisms behind the effects of climate change on coastal fish communities. In this study, fish monitoring data collected semi‐monthly between 1982 and 2019 from eight major bays in the northwestern Gulf of Mexico were analyzed with generalized additive models. Smooth patterns over seasons and years in the incidence data of 77 species were estimated, and the data were associated with environmental variables. Further, these temporal patterns were associated with the life‐history traits of species. The results show that species that are more common in the summer months (non‐winter spawners) tend to exhibit an increasing trend and that species common during the spring (winter spawners) tend to exhibit a decreasing trend, suggesting the importance of summer conditions in driving tropicalization. Salinity had significant effects on species in general, and longer‐lived species tended to be affected by temperature. These results suggest seasonal differences in the effects of environmental conditions and variation in sensitivity to environmental conditions among different life‐history strategies. These findings represent major steps toward understanding the mechanisms behind the tropicalization of estuarine communities.

Comparing Environmental DNA Metabarcoding and Underwater Visual Census to Monitor Korean Coastal Fish Community

Comparing Environmental DNA Metabarcoding and Underwater Visual Census to Monitor Korean Coastal Fish Community

How do El Niño Southern Oscillation (ENSO) Events Impact Fish Catch in Sarawak Water?

The response of chlorophyll to climate variability plays an important role in regulating the regional marine ecological environment and carbon cycle. This study focuses on the impact of changes in chlorophyll on the catches of deep-water fish and offshore fish. The chlorophyll factors from satellite image MODIS were analysed during La Niña in 2008/2011 and El Niño in 2015/2016. Remote sensing reflectance’s 443 nanometres and 555 nanometres were utilized to examine the bias of the chlorophyll concentration, Thus the higher phytoplankton absorption coefficient at 443, and backscattering coefficient for dissolved and detrital material stated the more phytoplankton biomass and higher suspended sediment concentration. The results found that the fish catch during El Niño is higher at 295572 metric tons compared to during La Niña which is 255783 metric tons. The El Niño event was found to have experienced an increase in catch of 29789 metric tons. This is due to the influence of the change in the mean value of the concentration in the study area of 0.31 mg-3 during La Niña compared to during El Niño 0.4 m mg-3. A decrease in the average value concentration of -0.09 mg-3 resulted in a decrease in the number of catches. In addition, the maximum value of chlorophyll concentration was also found to be high during El Niño which is 22 m mg-3 compared to during La Niña which is 18 m mg-3. The high distribution of chlorophyll-a is in the coastal areas of Sarawak, which explains why the coastal fish catches are higher than in the deep sea. It is concluded that the distribution of chlorophyll concentration is different during the occurrence of ENSO. This may result in different fishing rates in the study area. Remote sensing technology successfully explains why fish catches during El Niño are higher than during La Niña based on different chlorophyll dispersions. The provision of information in this space is very important to fishermen to reduce operating costs.