Academic literature on the topic 'Estuarine fish health'

Changing salinity in estuaries due to sea level rise and altered rainfall patterns, as a result of climate change, has the potential to influence the interactions of aquatic pollutants as well as to alter their toxicity. From a chemical property point of view, ionic concentration can increase the octanol–water partition coefficient and thus decrease the water solubility of a compound. Biologically, organism physiology and enzyme metabolism are also altered at different salinities with implications for drug metabolism and toxic effects. This highlights the need to understand the influence of salinity on pesticide toxicity when assessing risk to estuarine and marine fishes, particularly considering that climate change is predicted to alter salinity regimes globally and many risk assessments and regulatory decisions are made using freshwater studies. Therefore, we exposed the Inland Silverside (Menidia beryllina) at an early life stage to seven commonly used pesticides at two salinities relevant to estuarine waters (5 PSU and 15 PSU). Triadimefon was the only compound to show a statistically significant increase in toxicity at the 15 PSU LC50. However, all compounds showed a decrease in LC50 values at the higher salinity, and all but one showed a decrease in the LC10 value. Many organisms rely on estuaries as nurseries and increased toxicity at higher salinities may mean that organisms in critical life stages of development are at risk of experiencing adverse, toxic effects. The differences in toxicity demonstrated here have important implications for organisms living within estuarine and marine ecosystems in the Anthropocene as climate change alters estuarine salinity regimes globally.

It is well-known that climate change significantly impacts ecosystems (at the macro-level) and individual species (at the micro-level). Among the former, estuaries are the most vulnerable and affected ecosystems. However, despite the strong relations between climate change and estuaries, there is a gap in the literature regarding international studies across different regions investigating the impacts of climate change and variability on estuaries in different geographical zones. This paper addresses this need and reviews the impacts of climate change, variability and extreme weather on estuaries. It emphasises the following: (i) a set of climate parameters governing estuarine hydrology and processes; and (ii) a sample of countries in Asia (Bangladesh), Europe (Portugal) and South America (Uruguay). We reviewed the influences of the climatic drivers of the estuarine hydrology, ecological processes and specific species in estuarine communities across the selected geographical regions, along with an analysis of their long-term implications. The key results from the three estuaries are as following: (i) Hilsa fish, of which the catches contribute to 10% of the total earnings of the fishery sector (1% of GDP), are affected by climate-forced hydrological and productivity changes in the Meghna; (ii) extreme droughts and short-term severe precipitation have driven the long-term abundance and spatial distribution of both fish larvae and juveniles/adults in the Mondego; and (iii) the river inflow and fluctuations increases since the early 1970s have contributed to variations in the salinity, the stratification, the oxygen, nutrient and trophic levels and the spatial pattern for the life stages of planktonic species, fish biomass and captures in the Rio de la Plata. The results suggested that immediate action is needed to reduce the vulnerability of estuaries to climate stressors, mainly the changing river flows, storms and sea-level rise. As a contribution to addressing current problems, we described a set of adaptation strategies to foster climate resilience and adaptive capacity (e.g., early-warning systems, dam management to prevent overflows and adaptive fisheries management). The implications of this paper are two-fold. Firstly, it showcases a variety of problems that estuaries face from changing climate conditions. Secondly, the paper outlines the need for suitable adaptive management strategies to safeguard the integrity of such vital ecosystems.

Brackish water zones are areas with high ecological conservation value. In this study, 325 river estuaries in the Korean peninsula in individual sea areas (West Sea, South Sea, and East Sea) were divided into types of estuaries (upstream and downstream of open estuaries, closed estuaries) through the assessment of the health of the estuary aquatic ecosystems and fish communities were identified. An ecological assessment was carried out using the Korea Estuary Fish Assessment Index (KEFAI). The number of species increased as the size of the river increased in the case of small estuaries but gradually decreased in the case of large estuaries. In the closed estuaries, the relative abundances (RAs) of primary freshwater fish were the highest; however, in the open estuaries, the RAs of estuary fish were the highest. Non-metric dimensional analysis results suggested that there was a clear difference between the fish assemblages in the closed and open estuaries. The overall results of this study were that the RA of tolerant species was higher, and KEFAI was lower in closed estuaries than in open estuaries, indicating the negative effects of the construction of transverse structures on fish assemblages. The health of these estuarine ecosystems can be improved by addressing these negative effects.

Due to the sparsity in knowledge, we investigated the presence of various estrogenic endocrine-disrupting chemicals (EEDCs), including phthalates (PAEs), bisphenol-A (BPA), and nonylphenol (NP), as well as microplastics (MPs) in samples of the most widely consumed fish collected from different estuaries in northern Taiwan. We then proceeded to determine the likely contribution that this exposure has on the potential for health impacts in humans following consumption of the fish. Six hundred fish caught from five river estuaries (producing 130 pooled samples) were analyzed to determine how different factors (such as the river, benthic, pelagic, and migratory species) influence EEDCs’ contamination and the possible impacts on human health following typical consumption patterns. The predominant EEDCs was diethyl phthalates (DEP), bis (2-ethylhexyl) phthalates (DEHP), and di-iso-nonylphthalate (DINP) in fish, present at 52.9 ± 77.3, 45.3 ± 79.8, and 42.5 ± 79.3 ng/g dry weight (d.w.), respectively. Residual levels of NP, BPA, and MPs in the fish were 17.4 ± 29.1 and 1.50 ± 2.20 ng/g d.w. and 0.185 ± 0.338 mg/g d.w., respectively. EEDCs and MPs levels varied widely among the five river estuaries sampled due, in part, to differences in habitat types and the associated diversity of fish species sampled. For DEP, the Lao-Jie River and pelagic environments produced the most severely contaminated fish species, respectively. DEP residues were also associated with the burden of MPs in the fish. Based on our analysis, we predict no substantial direct human health risk by EEDCs based on typical consumption rates of estuarine fish by the Taiwanese people. However, other sources of EEDC exposure cannot be ignored.

This extensive study intends to assess the abundances of microplastics in estuarine fishes and to examine the spatial and temporal fluctuations in microplastic pollution in selected estuarine ecosystems, including those of the Thiruvananthapuram and Kollam districts. The presence of microplastics (those having a diameter of less than 5 mm) in the estuarine environment is a growing cause for alarm on both a national and international scale. To investigate this, between February 2020 and January 2022, we surveyed the seasonal deposition of microplastics in the stomachs of some estuarine fishes in Southern Kerala. Microplastics came in many forms that we were able to positively identify as polypropylene (PP), polyethylene (PE), polystyrene (PS), and others. Microplastics were extracted from fish samples taken at 16 sites across two years and categorised according to size, colour, type and polymer content. Microfibers of less than 1 mm in length were the most common type of microplastic discovered in fish; they likely originated in domestic washing machines or garbage. Fish in Southern Kerala may be at greater risk of contamination since microplastics are more readily available there than in most other studies across the world. To better understand the risks to fish and create effective control methods to prevent plastic usage and minimise its influence on the aquatic environment, we advocate for more research on microplastic collecting in estuarine environments. Elemental analysis of sediment samples gathered from these sites. The objective of this study is to identify the toxic elements may potentially be transmitted to fish through microplastics and humans eat plastic-tainted fish and are exposed to plastic particles which causes various health problems.

Background The Rio Doce estuary, in Brazil, was impacted by the deposition of iron mine tailings, caused by the collapse of a dam in 2015. Based on published baseline datasets, the estuary has been experiencing chronic trace metal contamination effects since 2017, with potential bioaccumulation in fishes and human health risks. As metal and metalloid concentrations in aquatic ecosystems pose severe threats to the aquatic biota, we hypothesized that the trace metals in estuarine sediments nearly two years after the disaster would lead to bioaccumulation in demersal fishes and result in the biosynthesis of metal-responsive proteins. Methods We measured As, Cd, Cr, Cu, Fe, Mn, Pb, Se and Zn concentrations in sediment samples in August 2017 and compared to published baseline levels. Also, trace metals (As, Cd, Cr, Cu, Fe, Hg, Mn, Pb, Se and Zn) and protein (metallothionein and reduced glutathione) concentrations were quantified in the liver and muscle tissues of five fish species (Cathorops spixii, Genidens genidens, Eugerres brasilianus, Diapterus rhombeus and Mugil sp.) from the estuary, commonly used as food sources by local populations. Results Our results revealed high trace metal concentrations in estuarine sediments, when compared to published baseline values for the same estuary. The demersal fish species C. spixii and G. genidens had the highest concentrations of As, Cr, Mn, Hg, and Se in both, hepatic and muscle, tissues. Trace metal bioaccumulation in fish was correlated with the biosynthesis of metallothionein and reduced glutathione in both, liver and muscle, tissues, suggesting active physiological responses to contamination sources. The trace metal concentrations determined in fish tissues were also present in the estuarine sediments at the time of this study. Some elements had concentrations above the maximum permissible limits for human consumption in fish muscles (e.g., As, Cr, Mn, Se and Zn), suggesting potential human health risks that require further studies. Our study supports the high biogeochemical mobility of toxic elements between sediments and the bottom-dwelling biota in estuarine ecosystems.

Seawater and fish were collected from nearshore (Pearl River Estuarine, PRE) and offshore (middle of the South China Sea, MSCS) regions of the South China Sea (SCS) to determine the heavy metals (HMs) pollution status and biomagnification characteristics. Results show that Cu in PRE seawater was moderately contaminated. Overall pollution risk of seawater were PRE (3.32) > MSCS (0.56), whereas that of fish was MSCS (0.88) > PRE (0.42). δ13C and δ15N exhibited distinguished characteristics for PRE and MSCS fish, indicating the diverse energy sources, nitrogen sources, and food web structures of nearshore and offshore regions. Cu was biomagnified whereas Pb and Ni were biodiluted in offshore fish. Hg presented significant biomagnification in both of nearshore and offshore fish. Finally, the target hazard quotient of Hg (1.41) in MSCS fish exceeded the standard limit, which was posed by high Hg concentration and consumption rate of offshore fish.

SUMMARYAs there is little evidence of pollution affecting the health of fish and shellfish on a global scale, this paper attempts to put into perspective the pollution/fish disease relationship by reviewing examples of studies and reports in the historic and current literature. Although there is no dispute that pollution can affect the health of aquatic organisms under laboratory conditions and may be responsible for the decline of populations of such animals in some inland waters and some estuaries, most of the evidence for pollution causing or increasing disease in fish in open waters is circumstantial. Historical data proves that almost all fish and shellfish diseases known today have been described since the end of the last century. However, it is also known that water pollution, especially in inland waters, has for the past 400-500 years been the result of urbanization and industrialization. This has resulted in some major rivers becoming devoid of or deficient in fish stocks. The concern that pollution may influence the health status of fish and shellfish stocks has increased over the past 20 years. Initial attention was paid to epidermal diseases, including fin-rot in demersal fish, and protozoan diseases in molluscs in the heavily polluted bays and estuaries in North America. As the interest in this subject spread, it became political, and often controversial, especially amongst the North Sea countries. The disagreements have largely been settled amongst scientists because international bodies, such as the International Council for Exploration of the Sea (ICES), established workshops to investigate sampling methods and disease-reporting techniques. Recommendations from those workshops have contributed to some form of standardization for field work and the subject, although largely subjective, has some objective approaches which are described. As there are variable, interacting biological and physical influences in the aquatic environment, it is difficult to establish the background prevalences of diseases in populations offish and shellfish. Examples of the influences of climatic changes are presented, and these show that short-term catastrophes can be directly related. However, a more long-term problem is water acidification resulting largely from anthropogenic activities. In parts of Scandinavia this has, and is, leading to decimation offish stocks in inland waters. In general, diseases in fish and shellfish are very localized, but there is concern amongst scientists that certain cancers, especially liver tumours, occurring in demersal fish inhabiting polluted estuarine and coastal waters, are related to the release of chemicals, e.g. hydrocarbons, pesticides and heavy metals. This subject is discussed in detail, with examples of the author's own studies in North Sea fish. It is concluded that cancers in fish are of extremely low prevalence, and only present in a very few species, and then only in the oldest animals. Though changes in disease pattern may well be an indication of adverse environmental effects, further research is necessary for conclusive evidence.

Microplastics, which are defined as small plastic particles smaller than 5 mm, have been found in various aquatic environments all over the world. In this study, we investigated the level of microplastics in the surface water and estuarine mullet Mugil cephalus from 23 estuary areas in the south of China. M. cephalus, due to its wide distribution and high tolerance, was selected as a candidate fish species for monitoring the ingestion of marine microplastics. The size, color, and type of all microplastics were recorded from the water and fish samples by stereomicroscope. The average abundance of microplastics was 18,261 items/m3 in the surface water, and 7.2 items/individual in fish. These alarming numbers revealed significant pollution due to microplastics in the environment. Fragments and minute-sized particles were the most common features found in both the water and the fish samples. Some impurities in the water sample were easily confused with microplastics, but regular forms on the surface of the impurity could be distinguished by using scanning electron microscopy (SEM). The shape, color, and size of the microplastics in the fish and water samples were similar, which suggested that the microplastics in the water might enter the organisms’ body, thereby affecting the health of aquatic species and even humans. Based on these findings, it is highly recommended that the monitoring and managing of pollution due to microplastics be addressed in the estuaries.

The overall aim of this thesis was to develop an approach for constructing and validating a fish-based, multimetric index for assessing the ecological health of estuaries in south-western Australia, and to apply that approach to the large Swan Estuary, which has been subjected to substantial anthropogenic pressures. The indices developed for nearshore and offshore waters are the first to be produced for Western Australian estuaries. They deliver a reliable, practical and cost-effective method for quantifying the status of estuarine health, thus providing managers with a sound basis for preventative management actions and a means for communicating ecosystem health implications to the wider public. An extensive range of potential fish community characteristics (metrics) were initially tested for their suitability for incorporation into the indices. These metrics included various measures of species composition, diversity and abundance, trophic and functional aspects of the assemblage, i.e. the contributions of different feeding and lifehistory guilds and, where relevant, sentinel species. An a priori hypothesis was formulated for each candidate metric, reflecting its predicted response to increasing ecosystem degradation. Two different approaches were trialled to identify the subset of metrics that were most sensitive to changes in environmental integrity and thus most appropriate for inclusion in an index of ecosystem health. The first approach sought to identify those metrics that showed the strongest responses to spatial differences in the quality of physical habitat, as quantified using a novel and independent measure of habitat degradation. Habitat quality was thus assessed at 136 nearshore sites throughout the estuary in spring 2007, using rapid visual survey techniques to assign scores for each of six habitat quality metrics. Scores for all physical habitat metrics were then summed to produce an overall habitat quality index score for each site. The results of graphical screening and various multivariate statistical techniques (PERMANOVA, PCA and CCorA) demonstrated that this approach failed to confirm hypothesised responses of the 5 candidate fish metrics to physical habitat degradation and was thus unsuccessful in selecting appropriate metrics. This applied even to sites where water quality conditions were similar. Moreover, the compositions of the fish assemblages did not differ significantly among habitat quality categories, either across the whole estuary or within its various regions. It is thus suggested that habitat quality influences the fish communities of the Swan Estuary at a broader scale than that at which it was assessed. As none of the candidate metrics were found to be sensitive to spatial differences in habitat quality at local scales, a novel alternative approach was employed to identify the metric subset that most consistently reflected temporal (inter-annual) changes at the ecosystem level, and was thus likely to be most sensitive to changes in ecosystem condition. This approach to metric selection relied on the assumption that the ecological condition of the Swan Estuary has varied over time in response to changes in the suite of stressors acting on the system. This assumption is supported by the fact that there has been considerable inter-annual variation in the severity of environmental perturbations affecting the estuary, including large phytoplankton blooms and hypoxic events, and consequently in their effects on ecological processes and biota including fish. Given the above assumption, and the associated uncertainty surrounding the nature and magnitude of temporal changes in the ecological condition of the Swan Estuary over the last few decades, the second approach to metric selection employed a combination of multivariate (DISTLM and BEST) and information-theoretic statistical approaches to assess both metric sensitivity to inter-annual changes in ecosystem condition, and the extent of metric redundancy. This approach allowed inferences to be drawn from the weight of evidence derived from multiple analyses of fish data sets collected using divergent sampling techniques throughout the estuary between 1976 and 2009. Responsive and parsimonious subsets of 11 and seven candidate metrics were thus selected for subsequent incorporation into multimetric health indices for the nearshore waters (< 2 m depth) and offshore waters (> 2 m depth) of this system. Reference conditions for each selected nearshore and offshore metric, representing the ‘best available’ values against which the previous, current and future 6 health of the Swan Estuary may be assessed and compared, were then established for each season and region of the estuary using 30 years of fish assemblage data recorded throughout that system. This included data collected during the current study, in which fish were sampled seasonally in the nearshore and offshore waters between 2007 and 2009, and in which the sampling locations, timing and net types employed replicated, as far as possible, those in all previous studies of fish assemblages in this system. However, prior to establishing the reference conditions for the nearshore metrics, the fish assemblage data recorded in those waters first required standardisation to minimise the effects of gear-induced bias that were attributable to the large differences in the characteristics of the seine nets used to sample the nearshore fish fauna of the Swan Estuary since the mid-1970s. A net selectivity study was thus conducted during spring 2008 and autumn 2009 in two main regions of the estuary to compare the compositions of fish samples collected using each of the different seine nets employed historically, i.e. 21.5, 41.5 and 133 m–long seines. The data from these samples were then subjected to generalised linear modelling techniques to derive net equivalence factors for quantitatively standardising fish species abundance data across all historical and current nearshore samples, and thereby minimise the effects of sampling biases. Scoring thresholds were then determined statistically from the 5th and 95th percentiles of the composite nearshore and offshore fish assemblage data sets, enabling each metric in each sample to be scored according to the extent of its deviation from the relevant reference condition. Finally, index scores for both nearshore and offshore health indices were calculated by summing the scores for their component metrics and then adjusting the resultant value by the number of metrics in the index to produce a final, easily interpretable index score ranging from 0-100. Thresholds for establishing the qualitative health status of the estuary (i.e. good, fair, poor, very poor) were also determined by subdividing the possible range of index scores into four equal classes. The trends exhibited by the mean index scores for nearshore waters of the Swan Estuary suggest that the health of those waters has remained relatively constant over the last three decades, with their health status being classified as fair throughout this time. It is important to recognise, however, that interpretation of these trends in mean scores is 7 hindered by differences in the spatial distribution, timing and intensity of sampling among studies, and most notably among those from the mid-1970s to the mid-1990s. Interpretations of trends in the index scores for nearshore waters from the mid-1990s to the present are more reliable, due to greater similarities in the sampling methodology throughout this period. Such trends suggest that the health of these waters has increased in recent years, with the mean health index score increasing from ca 58 in 2005/06 to 64 in 2008/09. In contrast, the mean offshore index score has decreased consistently from 56.5 in the late 1970s to 47 in 2008/09, resulting, for the first time in three decades, in the health status of the offshore waters being classified as poor. The reliability of the nearshore and offshore indices was evaluated by quantifying the variability of index scores among replicate sites, within and between seasons and between consecutive years. The effects of random sampling variation on the precision of index scores were also determined using bootstrap resampling techniques. The sensitivity of the final nearshore and offshore indices to environmental degradation and other stressors was tested by determining the degree to which the health index scores for each replicate sample responded to three water quality parameters measured during sampling and, in the case of the nearshore index, to habitat quality metrics assessed in spring 2007. Although index responses to changes in specific stressors were not detected, the consistent decrease in offshore health index scores from 1978 to 2009 suggests that this index is capable of detecting the widely-perceived, longterm decline in the condition of offshore waters of the Swan Estuary. Moreover, the far greater inter-seasonal variability among offshore than nearshore index scores provides further evidence that the deeper waters of the estuary are in poorer health than the shallower waters, most notably in the upper reaches of this system. The consistently lower spatial variability of nearshore and offshore index scores recorded in summer and autumn indicates that, dependent upon an appropriate examination of intra-seasonal index variability, these seasons represent a suitable index period for future monitoring of the ecological health of the Swan Estuary. Overall, validation of the indices developed during this study demonstrated that their spatial and temporal variability was comparable to that of existing multimetric indices employed in 8 the USA and Europe, and that classification of the health status of the estuary was fairly robust, despite the effects of both natural spatio-temporal variability and sampling error on index scores. Given the relative lack of quantitative, biological indicators currently available to estuarine managers, there is considerable potential for multimetric, biotic indices to advance the field of estuarine health assessment in Australia. Several issues must be addressed if we are to understand the complex ways in which the condition of these estuarine systems responds to natural and anthropogenic pressures or to management actions designed to improve or maintain them, not least of which is the need for such indices to be integrated within a broader monitoring framework employing multiple indicators.

The aims of this study were to determine the potential use of biomarkers at multiple levels of biological organisation together with a fish community bioindicator to assess the estuarine health status of three temporarily open/closed estuaries. The estuaries investigated were the East Kleinemonde (EK), Old Woman's (OW) and Mtana (MTN), all of which are situated in the Eastern Cape Province. Three biomarkers, the acetylcholinesterase (AChE) assay, lipid peroxidation (LPx) assay, liver histopathology and a condition factor were used to determine sub-organism health and one bioindicator, the Estuarine Fish Community Index (EFCI), was used as a bioindicator of community health. The estuarine-dependent marine species Rhabdosargus holubi was selected as an indicator species for the sub-organism level analyses. The results from the community analyses indicated that the EK and OW estuaries were in 'good' condition, while the MTN was found to be in 'moderate' condition. Histological analyses revealed that R. holubi from all three estuaries showed signs of pathological changes to the liver, with the fish from the MTN eliciting the highest occurrence of these changes. The LPx assay found that R. holubi from both the OW and MTN showed signs of oxidative damage in the liver tissue, but those from the EK did not appear to be affected. The AChE assay showed that only the fish from the OW had been affected by anticholinesterase compounds. A laboratory study was undertaken using R. holubi as a positive control for the AChE and LPx assay. The fish were exposed to 3 μg/L chlorpyrifos, a known cholinesterase inhibitor, for six hours and their tissues were examined for changes to LPx levels and AChE activities. AChE activity was significantly inhibited (Mann Whitney U test, Z = 3.65, n = 38, P < 0.001) by the exposure, but LPx levels were not significantly affected. A composite index incorporating the biomarkers at different biological levels of organisation was developed. The index was designed to assist managers and scientists to determine whether the ichthyofauna of a system was being affected by environmental stressors and what management interventions could be undertaken to ameliorate the water quality in an estuary. The index was applied to the three estuaries investigated during the present study and both the OW and MTN were assessed to be in need of immediate management intervention. The fish in the OW were found to be stressed at all the sub-organism levels measured and the reason for this was hypothesised to be as a result of golf course activities in this adjacent estuary. A number of management actions are proposed to reduce the sub-organism stress observed in the fish from the OW. The livers of fish from the MTN were shown to be under stress; however the causative agent of this stress was unknown because there is no formal development in the MTN catchment. However, a possible contaminant source is proposed and management interventions to alleviate the stress on the biota of the MTN are suggested. The EK does not require immediate management intervention, however, continuous routine monitoring is recommended to ensure that conditions do not deteriorate. Shortcomings of the index were outlined and a number of suggestions were made in terms of other measures of biological health which could be incorporated into the index.

Aquaculture is an important economic activity the world over and about 90% of the global production is contributed by Asian countries. Global aquaculture has a persistent goal to maximize the production with optimal profit. Even though the aquaculture is growing at a rapid rate, the practice of aquaculture faces many challenges in its developing path. Intense cultivation in high densities significantly affect the environment by issues of used - up farm water discharges and heavy waste accumulation through hyper nutrification due to excessive feeding and high dietary nutrient composition (Liao and Mayo 1974; Boyd 1985). This has brought stress to the rearing environment and diseases to the cultured species and subsequently decreased the overall productivity due to mass mortality which has led to significant loss to the industry (Irie et al. 2005; Cruz et al. 2012; FAO 2012). Thus, it is necessary to face the challenges and find solutions in order to make aquaculture sustainable. Disease is the result of interaction between the host, pathogen and external environment. At the onset of disease, the harmonious interplay between pathogens and non-pathogens is disturbed result in unhealthy host and thereby infection occurs (Verschuere et al. 2000; Schulze et al. 2006; Zhou et al. 2009; Nemutanzhela et al. 2014). Bacteria, fungi, viruses and parasites are the major pathogens affecting aquaculture industry. Among different aquaculture pathogens, bacteria play a major role. It can survive and flourish independently in any aquatic environment. The bacterial fish infections are mainly from the species of Aeromonas, Vibrio, Flavobacterium, Edwardsiella, Yersinia, Pseudomonas, Streptococcus, Renibacterium, Piscirickettsia, Mycobacterium etc. The common bacterial disease symptoms are external reddening and haemorrhage in the peritoneum, body wall and viscera, generically referred to as haemorrhagic septicaemia. The progress of disease leads to ulcerative lesions and mortality of untreated cultured animals (Pridgeon and Klesius 2012). Among the bacterial diseases, vibriosis is caused by a major bacterial fish pathogen Vibrio spp. which is ubiquitous in all aqua cultured species (Jayaprakash et al. 2005; Thompson et al. 2010). In tropical countries, penaeid shrimp culture is highly affected by V. harveyi which causes their mass mortality (Austin & Zhang 2006). Another Vibrio species which affects the shrimp culture are V. alginolyticus, V. damsela, V. parahaemolyticus, V. vulnificus, V. splendidus and V. penaeicida (Saulnier et al. 2000).

<em>Abstract.—</em> It cannot be denied that habitat is essential to healthy fish populations. A significant number of fish species in the Gulf of Mexico and around the country depends on estuaries during some stage of their life cycles. Despite this fact, fish habitats are increasingly destroyed and degraded by pollution, dredging, freshwater influx, and other human activities. If healthy fish populations are to be maintained, threats to fish habitat must be addressed. However, traditional management practices have neglected and continue to ignore threats to important fish habitat. The essential fish habitat (EFH) provisions of the 1996 Magnuson-Stevens Fishery Conservation and Management Act (Magnuson-Stevens Act) present an unprecedented opportunity to develop habitat-based management approaches to protect and restore important fish habitats in the ocean and in vital estuarine areas. This is not to say the EFH provisions of the Magnuson-Stevens Act are a panacea for habitat protection. For example, there is no enforceable mechanism for preventing activities that destroy areas of EFH. Nonetheless, the EFH provisions of the Magnuson-Stevens Act can go far in achieving the intended results if the National Marine Fisheries Service (NMFS) promulgates guidelines requiring ecosystem-based management, if regional EFH amendments go beyond minimalist requirements to address threats to habitat through comprehensive habitat management plans, and if regional fishery management councils become important players in the host of federal decisions that affect fish habitat. The NMFS and the regional fishery management councils must be required to take full advantage of this unique opportunity.

<em>Abstract.—</em> It cannot be denied that habitat is essential to healthy fish populations. A significant number of fish species in the Gulf of Mexico and around the country depends on estuaries during some stage of their life cycles. Despite this fact, fish habitats are increasingly destroyed and degraded by pollution, dredging, freshwater influx, and other human activities. If healthy fish populations are to be maintained, threats to fish habitat must be addressed. However, traditional management practices have neglected and continue to ignore threats to important fish habitat. The essential fish habitat (EFH) provisions of the 1996 Magnuson-Stevens Fishery Conservation and Management Act (Magnuson-Stevens Act) present an unprecedented opportunity to develop habitat-based management approaches to protect and restore important fish habitats in the ocean and in vital estuarine areas. This is not to say the EFH provisions of the Magnuson-Stevens Act are a panacea for habitat protection. For example, there is no enforceable mechanism for preventing activities that destroy areas of EFH. Nonetheless, the EFH provisions of the Magnuson-Stevens Act can go far in achieving the intended results if the National Marine Fisheries Service (NMFS) promulgates guidelines requiring ecosystem-based management, if regional EFH amendments go beyond minimalist requirements to address threats to habitat through comprehensive habitat management plans, and if regional fishery management councils become important players in the host of federal decisions that affect fish habitat. The NMFS and the regional fishery management councils must be required to take full advantage of this unique opportunity.

<em>Abstract</em>.—Nonpoint source pollution in the form of stormwater runoff is one of the most important emerging threats to ecosystems along the coastal margins of the United States. A wide diversity of potentially toxic chemicals is commonly found in stormwater. These include the various pesticides, petroleum hydrocarbons, heavy metals, and other common contaminants that originate from commercial, industrial, residential, and agricultural land-use activities. These chemicals are mobilized from roads, lawns, crops, and other surfaces by rainfall and then transported to aquatic habitats via terrestrial runoff. The ongoing development of coastal watersheds nationwide is increasing the loading of nonpoint source pollutants to rivers, estuaries, and the nearshore marine environment. A central aim of the National Oceanic and Atmospheric Administration’s national Coastal Storms Program (CSP) is to enhance the resiliency of coastal ecosystems by improving the ability of coastal communities to anticipate and reduce the impacts of contaminated terrestrial runoff. Toxic chemicals in stormwater can adversely impact the health of fish, including threatened and endangered species. Nonpoint source pollution can also degrade the biological integrity of aquatic communities that support productive fish populations. This article examines the effects of stormwater runoff on fish and fisheries. Using case studies drawn from CSP project work in the Pacific Northwest and Southern California pilot regions, we show how degraded water quality can impact the health of fish during critical life history stages (i.e., spawning and rearing) as well as limit the overall effectiveness of fish habitat restoration. We also discuss some of the resources currently available to local communities to reduce the loading of toxics in stormwater, thereby increasing the resilience of aquatic communities. Finally, we identify priority areas for new research to help guide the future conservation and recovery of at-risk fish populations.

The Durankulak Lake is the northernmost Bulgarian Black Sea lagoon. The hydrological regime of the lake is, for the most part, the inflow of water in karst underground cracks. Over the years, the rare cases of digging a sea-lake canal have been a significant cause of the oligohaline estuarine wetlands nature of the water body. The publication aims to present current research on the structure of the lake bottom, the heart of the substrate and changes over the years, using data from a multi-beam echo sounder and side-scan sonar, as well as new data for ichthyological fauna. In the period 2020-2021, the lake was monitored, including key physicochemical indicators, which indicate an increase in the period of eutrophication due to changes in climatic conditions and the impact of anthropogenic pressure. The average salinity of lake waters is approximately 2 ppm salinity, with a maximum at the end of summer - 4 ppm salinity and a minimum in spring - 1 ppm salinity. The average data of the other physicochemical indicators are the following: T�C-13.5, pH-8.48, O2 ml/ - 7.52 for the period 2019 - 2021. The hydrological and hydromorphological features of Durankulak Lake are crucial for the composition of its fish fauna, which is mainly composed of freshwater and brackish forms. The fish that inhabit the year-round Durankulak Lake belong to several faunal complexes. In the first place is the complex of primary freshwater, which is represented by nine species belonging to the families Cyprinidae (6 species), Siluridae (1 species), Gasterosteidae (1 species) and Gobiidae (4 species). The group of Mediterranean immigrants, represented by only one species of the family Syngnathidae, is the least represented.