Sea Fish Species Research Articles

Fish Consumption Frequency in the Adult Population in Poland

Fish provide energy, protein, and other important nutrients, including n-3 fatty acids, vitamin D, and iodine. However, some species of fish could contain contaminants such as mercury and dioxins. The aim of the study was to assess the frequency of fish consumption in Poland, including of sea and freshwater fish species, referring to some socio-economic determinants. The frequency of consumption was assessed using Food Propensity Questionnaire data from 1489 adults (722 males, 767 females) in 2019–2020. The fish consumption frequency in Polish adults was lower than the recommendation (at least twice a week). About 80% of respondents consumed fish less frequently than recommended. Sea fish were mostly consumed less than once a month (31.8%) or 1–3 times a month (30.9%). Most subjects (44.8%) consumed freshwater fish less than once a month. Consumption also depended educational level, economic status, place of residence, declared health status, and BMI value or BMI status. However, taking into account sex, the occurrence of these relationships was different between men and women. It seems that educational activities and dissemination of proper nutrition principles is necessary in order to increase the consumption of fish in Poland. It is important to emphasize the health benefits of fish consumption in relation to the possible adverse effects of their contamination.

First report of the presence of Pseudoterranova sp. in the body cavity of salmon (Salmo salar) from the Baltic Sea

Abstract Despite salmon (Salmo salar L.) being an important fish in the Baltic Sea ecosystem and its fisheries, knowledge about the parasite fauna of this top predator is scarce. The Anisakidae nematodes (Anisakis spp., Pseudoterranova spp., Contracaecum sp.) found in Baltic Sea fish species are zoonotic parasites that are hazardous to human health. Due to the marked increase in the numbers of grey seal (Halichoerus grypus), the definitive host of Contracaecum sp. and Pseudoterranova spp., increased dispersion of these parasites has been observed in recent years. The aim of our study was to investigate salmon caught in Polish marine waters for the presence of Anisakidae nematodes. Parasitological inspection of the body cavities of 89 individual salmon was conducted in 2012 and revealed the presence of a Pseudoterranova sp. L3 larva. The presence of the parasite is reported here for the first time in the muscle tissue of salmon from the Baltic Sea. The presence of Anisakidae nematodes in commercially important fish species may have implications for human health since these parasites pose a risk of anisakidosis.

Trophic niche overlap of deep-sea fish species revealed by the combined approach of stomach contents and stable isotopes analysis in the Central Tyrrhenian Sea

Understanding the trophic ecology of marine ecosystems is a key challenge given that they are subject to anthropogenic pressures that can alter the integrity of the food web. The bathyal zone of the Central Tyrrhenian Sea is characterized by an high level of community biodiversity, heavy anthropogenic pressure and thus represents a fundamental environment for the study of trophic relationships between demersal fish species which live in sympatry, but this basin still remains data deficient. To fill this information gap, we investigated the trophic niche overlap of four deep-sea fish species, Galeus melastomus, Helicolenus dactylopterus, Lepidorhombus boscii, and Trisopterus capelanus, in the Central Tyrrhenian Sea using an integrated approach of stomach content and stable isotopes analysis (δ13C and δ15N). Our analysis revealed that the blackmouth catshark G. melastomus displays a wide trophic niche with considerable overlap with other fish species, as it consumed diverse prey including fish, crustaceans, and cephalopods, thus proving a generalist and opportunistic feeding behavior. The blackbelly rosefish H. dactylopterus exhibits a narrower isotopic trophic niche comprising mainly benthic crustaceans and so suggesting a marked specialism in feeding strategy. The diet of the four-spotted megrim L. boscii showed a marked overlap with that H. dactylopterus, as these species shared a similar benthic habit and relied upon a similar pool of resource. The poor cod T. capelanus showed a diverse diet comprising both prey captured close to the bottom, especially decapod and mysid crustaceans, and bathypelagic prey, mainly Osteichthyes, Myctophidae, and amphipod Hyperiidae, with an intermediate partially segregated isotopic niche width. The combination of stomach content analysis and stable isotopes analysis provided the first characterization of the trophic relationships, shedding light on the trophic niche overlap of these four ecologically important deep sea fish species. The diets of the four investigated species showed similarities in the composition of prey, but also differences which allows them to partially reduce competition. This information may be of crucial relevance for the development of effective management and conservation strategies for the bathyal Mediterranean environment.

Thalassotherapy as a multidirectional form of marine resources therapy

Thalassotherapy is a treatment that uses the natural gifts of the sea (climate, air, sea sand, algae, some species of sea fish, mother of pearl) and physical factors (hydrotherapy, heliotherapy, aerosol therapy, music therapy, kinesitherapy and others). It is mainly intended for people who are stressed, overtired and have sleep problems. Thalassotherapy is also used in the treatment of rheumatism, back pain, lung diseases, heart diseases and skin dermatoses, such as psoriasis or atopic dermatitis. These treatments are widely used in wellness centers as care and therapeutic treatments for problematic skin. In cosmetology, preparations of marine origin are also used in the form of masks, peeling creams intended for dry, oily, gray, mature or poorly nourished skin.

Microplastic Pollution in the Gastrointestinal Tract and Gills of Some Teleost and Sturgeon Fish from the Caspian Sea, Northern Iran.

The increasing microplastic pollution in the marine environment has raised global concern. The main risk of microplastics in aquatic ecosystem is their bioaccumulation in aquatic organisms. A few studies have reported microplastic pollution in the digestive system of Caspian Sea fish species, but there is no research on sturgeon species, nor on fish gills. We investigated the occurrence of microplastics in the gastrointestinal tract (GIT) and gills of 62 specimens belonging to four species including three teleosts (Cyprinus carpio, Rutilus kutum, and Chelon aurata) and one sturgeon (Acipenser persicus, a valuable endangered species) from the Caspian Sea between January and March 2022. Fish tissues were removed, exposed for 24 h to 10% KOH, and then dried on filter paper. Particles were observed under a stereomicroscope and analyzed by Raman microspectrometry, scanning electron microscopy, and energy-dispersive spectroscopy. A total of 91 microplastics were detected in the GIT (average of 1.46 ± 1.17 items/individual) and 63 microplastics in the gills (average of 1.01 ± 0.62 items/individual). A significant correlation was not found between the number of microplastics found in both tissues and fish body length, body weight, GIT weight, and gill weight (p > 0.05), except between microplastics isolated from gills and gill weight in C. carpio (rs = 0.707, p = 0.022). The abundance of microplastics in fish followed the order of A. persicus > C. aurata > R. kutum > C. carpio. The microplastics were in the size range of 45 to 5000 µm, with particles of 300 to 1000 µm being the most prevalent; 74.68% of the particles were shaped like fibers, 30.53% were red, and 70.6% were composed of nylon polymer. Environ Toxicol Chem 2023;42:2453-2465. © 2023 SETAC.

Microplastic distribution in different tissues of small pelagic fish of the Northeast Atlantic Ocean

The accumulation of microplastics (MP) by marine species of ecological and commercial interest represents a major concern, particularly for those present in human diet. This study analysed the accumulation of MP in three species of coastal pelagic fish with high commercial value, European sardine (Sardina pilchardus), European anchovy (Engraulis encrasicolus) and horse mackerel (Trachurus trachurus), collected along the Western coast of the Iberian Peninsula. The gastrointestinal tract (GT), gills and muscle were analysed and a total of 504 particles were observed. MP were found in all target tissues of the studied species. Horse mackerel exhibited significantly higher concentrations of microplastics in GT compared to other tissues. On the other hand, anchovies and sardines had significantly lower microplastic concentrations in their muscle tissue. The accumulation of microplastics in the gills showed a significant difference between species, with anchovy having significantly higher concentrations compared to horse mackerel. Horse mackerel had the highest percentage of individuals with microplastics in their GT (92 %), followed by sardine (75 %) and anchovy (50 %). Horse mackerel was also the species that registered the highest percentage of individuals with particles in the muscle (63 %), followed by anchovy (40 %) and finally sardine (39 %). MP in the gills of European sardines and anchovies were similar to those found in water samples. The majority of MP found measured <0.5 mm and were blue fibers. Furthermore, the presence of MP in the GT showed a weak and moderated significant negative correlation with the Fulton Condition Index in horse mackerel and European sardine. Our study confirms the ubiquitous extent of MP contamination in the ocean and provides baseline evidence of MP tissue distribution in three small pelagic fish species with distinct feeding behaviour, while correlating this with the presence of MP in water. Importantly, the results of this study contribute to improve the understanding of biological partitioning of MP in open sea fish species with high commercial relevance, and the potential deleterious effects of our increasingly MP contaminated world.

The use of radiocarbon to evaluate the trophic role of geothermal bacteria in shallow hydrothermal water ecosystem

Stable isotopes such as δ13C and δ15N are routinely used in trophic ecology as isotope values are derived from diet and recorded subsequent fractionation in consumer tissue. However, this approach necessitates to estimate a priori the fractionation between food source and consumer leading to potential uncertainties. In this context, the development of additional biomarkers enables to have better resolution on feeding habits. Dissolved Inorganic Carbon (DIC) from volcanic activity and bacteria using this DIC presents a strongly depleted natural radiocarbon abundances (Δ14C). Through its activity, the geothermal plant of Bouillante in Guadeloupe (French West Indies) releases sulfur bacteria in shallow environment of the Bay. A previous study reveals ingestion of those bacteria by opportunist species (sea urchin and fish species). In the present study, ten species with different diet and feeding mode were sampled close to the release channel of the geothermal plant and in a control station in order to simultaneously determine their stable isotopes (δ13C and δ15N) and radiocarbon compositions. Compared to models using Δ14C data, models using δ13C and δ15N data underestimate the role of bacteria in diet of urchin and fish species whereas this role is overestimated for all other species. Compared to previous models, radiocarbon would give more realistic and reliable results than the classical use of stable isotope. This study confirms the utility of radiocarbon in food web ecology, particularly at the ecosystems having food sources with contrasting Δ14C values.

Diversity and characteristics of commercial Red Sea fish species based on fish market survey: informing management to reduce the risk of overfishing.

In small-scale fisheries (SSFs), where the sampling of many small boats and landing sites sometimes is not practical, fish market surveys represent an alternative way to obtain key fisheries data. This study analyses the diversity and characteristics of commercial Red Sea fish species landed in the Egyptian coast, including family, species-specific abundance, biomass, size and price by surveying the largest local fish market on the Egyptian Red Sea coast, over the course of a year (July 2021-June 2022) to also reflect any seasonality of these variables. Based on 53 survey visits, a total of 131,795 fish individuals, belonging to 111 species, and 22 families, were identified, recorded and measured. The analysis focused on the 60 most abundant species (104,420 individuals, 15 families). The surveys revealed that the most abundant families were Serranidae, Lethrinidae and Scaridae. Carangidae also was one of the most important families in terms of biomass. The most abundant species were Lethrinus mahsena, Sargocentron spiniferum and Lethrinus nebulosus. About 60% of revenue comes from the four families Serranidae, Lethrinidae, Scaridae and Lutjanidae. In terms of prices, the most expensive categories were species belonging to Serranidae, Lethrinidae and Lutjanidae families, such as Plectropomus pessuliferus marisrubri, Argyrops spinifer, L. nebulosus and Variola louti. The overall mean prices were higher in spring and summer months likely due to tourism flows. The mean size of many species, including the most valuable and abundant ones, is below the length of maturity. These results provide important benchmarks for monitoring future changes and shed important insights for fisheries management. Co-organised Dutch auctions would provide reliable data when combined with a strict monitoring effort to avoid any sale of the catch outside these official auctions. Other monitoring tools and methods are also recommended in the discussion.

Bioaccumulation of natural radio-nuclides in aquatic, riparian and terrestrial animals along Suez-Azzafrana coastline, Egypt: insights from RESRAD-BIOTA

Purpose The protection of endogenous species is one of the important ecological issues in which all the World Environmental Agreements are searching for. The purpose of the study is to calculate the bioaccumulation impacts of some natural radio-nuclides as: Ra-226, K-40 and Th-232 in the selected Egyptian Endogenous Aquatic Red Sea Fusileer fish, Red sea Riparian Turtle and the Red sea Terrestrial Lizard by using RESAD BIOTA version 1.8. Material and methods Ten water and sediments samples were collected from different 10 sites, along the inshore of the Egyptian Suez bay beach till El-Zafarna coastal region, as these samples were taken from subsurface (20 cm–1 m). The radioactivity concentrations of some natural radioactivity radionuclides as; 226Ra, 232Th and 40K, which were measured, using gamma-ray spectrometer based on high-purity germanium (HPGe) detector of 40% relative efficiency. Results The results of the study showed that the radioactivity of some selected natural radionuclides in the selected 10 sites of Suez costal samples were arranged as: K-40 > Th-232 > Ra-226, as this was related to the characteristics of soil and rock precipitation in this zone besides the industrial activates along the selected coastal line zone of Suez bay till Al-Zafrana. On the other hand, it was observed that all the calculated Biota contamination Guide (BCG) values of the selected Egyptian endangerous species (Aquatic, Riparian and terrestrial) animals in the 10 selected sites samples were below the recommended (BCG), as the result, no radioactivity increment being detected at these selected sites. On the other hand, the BCG values of Ra-226 in both water and sediment samples for the selected Egyptian endangerous Aquatic Sea Fusileer Fish were higher than the recommended BCG values in water, while were comply with BGC values of the sediment, while in case of Egyptian endangerous Red Sea Turtle’s BCG values were comply with the recommended BCGs in water while were higher than the recommended BCGs values of sediment. In case of the selected Egyptian endangerous terrestrial Lizard its BCG values of Ra-226 were higher than the recommended BCGs in both water and sediment media. While in case of Th-232 it was observed that the BCG values of selected endangerous Red Sea Fusileer Fish were higher than the recommended BCGs in both water and sediment and also the BCG values of selected endangerous Riparian Turtle were also higher than the recommended BCGs of both water and sediment, these results may increase the suitability of the selected Egyptian endangerous Marine, Riparian and Terrestrial species to the different radiological risks. The results showed also the decrement of the radioactivity values of the measured radionuclides in the internal tissue of the Egyptian selected endangerous Red Sea Lizard (Uromastyx aegyptia) than both the selected endangerous Red Sea Turtle and Red Sea Fish species, support the reptiles, which are cold blood animals, and is less affected by gamma radiation than other terrestrial animals.

Heavy metal contamination of Diplodus vulgaris (Sparidae) in the Gulf of Annaba (North-eastern Algeria)

The aim of this work was to evaluate heavy metals (Lead and Cadmium) contamination in the muscles ofa local sea fish species, the black-headed Sar Diploddus vulgaris. We selected two sites in the Gulf of Annabafor this study (Sidi Salem fishing site and the Port of Annaba) and compared results to a reference site (Capde Garde), which is at a valuable distance from any source of pollution, and is considered as a relativelyclean site, while Sidi Salem and Port of Annaba are known to be exposed sites to various sources of industrial,urban and harbor pollution. Analyses have been carried out on 70 samples of dorsal-lateral muscles offishes weighting from 30 g to 280 g and sizing between 11.1 cm to 26.5 cm. The results showed the presenceof both metals in all samples during the 6 months of our study (from November to June) and in the 3 siteswith variable rates. Cadmium levels varied from 0.032 to 0.239 mg/kg/fw. Fish meat from Sidi Salem collectedduring the months of November and February displayed a rate of 0.038-0.074 mg/kg/fw of Cd beforereaching a higher value in March estimated to 0.202 mg/kg/fw of Cd. From April to June, the lateral dorsalmuscles were contaminated by lower Cd contents. Pb concentrations varied from 0.014 to 0.149 mg/kg/fw.The highest value was recorded during the month of March at Sidi Salem. Moreover, Pb concentrations inmuscle tissues increased significantly compared to the other studied sites. Very high significance differenceswere found between Cap de Garde and Port of Annaba and Sidi Salem for both metals (Pb and Cd). Toconclude, the presence of heavy metals in Diplodus vulgaris is due to the diet and the impact of anthropogenicactivities on the biotope of the fish and therefore poses a public health problem linked to frequentconsumption of this fish. Also, D. vulgaris appears to be a suitable sentinel species for the assessment ofecotoxicological risk in the Gulf of Annaba.

A study of the microbiology of the intestinal tract in different species of Teleost fish from the Black Sea

This paper presents a study on the microbial status of different fish species and their habitats in the Bulgarian Black Sea area. The samples were collected in the period of January 2021 until March 2021. The fish species we used in this study were Black Sea turbot (Scophthalmus maximus), round goby (Neogobius melanostomus), shore rockling (Gaidropsarus mediterraneus) and European anchovy (Engraulis encrasicolus). The BIOLOG system was used for microbiological determination. From the different fish species, different species of microorganisms were isolated (using selective nutrient media). From the torbut, we isolated species Enterococcus villorum with 24 × 103 cells in 1 ml, Moraxella nonliquefaciens with 70 × 103 cells in 1 ml and Pseudomonas synxantha with 123 × 103 cells. Pseudomonas putida was isolated from the round goby with 20 × 103 cells in 1 ml. The species Streptococcus entericus with 123 × 103 cells in 1 ml was isolated from the shore rockling. Pseudomonas fulva with 60 × 103 cells in 1 ml was isolated from the European anchovy. A total of 223 × 103 cells in 1 ml of Pseudomonas agarici were isolated from Trachinus draco. Pseudomonas tolaasii with 145 × 103 cells in 1 ml were isolated from Merlangius merlangus. A different species of bacteria of the genus Pseudomonas was found for each of the investigated species of Black Sea fish. Apparently, the species Pseudomonas is characteristic of marine Teleostei and is important for the life and metabolism of these vertebrates. These microorganisms probably are resident species and developed not as result of pollution or environmental change.

Element concentrations of cultured fish in the Black Sea: selenium-mercury balance and the risk assessments for consumer health.

Fish are a powerful model for risk-benefit analyses to explore the impact of elements on human health among all accessible species. The sea bream (Sparus aurata), sea bass (Dicentrarchus labrax), turbot (Scophthalmus maximus), and weights of > 1kg large rainbow trout registered as "Turkish Salmon," (Oncorhynchus mykiss) are four economically important cultured species in the Black Sea In this research, it is aimed (1) to determine the value of the elements, (2) to determine total Hg and Se concentrations, Se/Hg molar ratios, and the HBVSe index, and (3) to calculate the consumer's possible health risk in the edible tissues of cultivated four economically important Black Sea fish species. Fish and diet samples from all species were obtained in 2020 from aquaculture locations in the Black Sea (Sinop, Samsun, and Trabzon cites of Turkey). At the end of the study, the elements in all edible tissues and all the parameters analyzed [Se/Hg, estimated daily intake (EDI), target hazard quotient (THQ), maximum allowable consumption rate (CRlim and CRmm)] in cultured fish tissues were below permissible values. Additionally, when compared with the data of the World Health Organization and The National Academy of Sciences, it determined that consuming cultured fish in the Black Sea adequately meets the daily elemental requirement.

Habitat suitability models of five keynote Bulgarian Black Sea fish species relative to specific abiotic and biotic factors

Over the past few years, predicting species spatial distributions has been recognized as a powerful tool for studying biological invasions in conservation biology and planning, ecology, and evolutionary biology. Species spatial distribution models (SDMs) are used extensively for assessing the effects of changes in habitat suitability, the impacts of climate change, and the realignment of the existing conservation priorities. SDMs relate known patterns of species occurrences to a specific set of environmental conditions. Accordingly, we have used MaxEnt SDM tool in order to provide habitat suitability models of 5 keynote fish species: European sprat (Sprattus sprattus L.), red mullet (Mullus barbatus, L.), horse mackerel (Trachurus mediterraneus, L.), bluefish (Pomatomus saltatrix, L.) and whiting (Merlangius merlangus, L.), inhabiting the Bulgarian region of the Black Sea. Presence-only (PO) data collected by pelagic surveys performed between 2017 and 2019 was further utilized to link known species occurrence localities with selected abiotic factors, such as surface sea temperature and salinity, dissolved oxygen, and speed of currents. Biotic interactions were also considered for fitting the patterns of habitat suitability models. The SDMs, obtained from the present research study, prove to have satisfactory predictive accuracy to be further implemented for conservation measures and planning, stock management policy-making, or ecological forecasting.

Praniza (Isopoda: Gnathia) Parasitic on Gills of Arabian carpetshark Chiloscyllium arabicum with Notes of its Occurrence on some Marine Fishes of Iraq

Praniza larvae of Gnathia sp. were reported on the gills of 18 Iraqi sea fish species. Hosts were eight elasmobranchs and 10 teleosts. Cartilaginous hosts belong to four families, with highest mean prevalence was 100% in Pastinachus sephen, while the lowest prevalence was 25% in Gymnura poecilura. Teleost hosts belong to seven families, the highest prevalence was 50% in Rabdosargus haffara and the lowest was 1.6% in Tenualosa ilisha. The higher mean intensity of infection was 12.3 in Chiloscyllium arabicum, and only one in all teleost fish species. Praniza parasite of C. arabicum has long body, concave cephalon, narrowing anteriorly with truncate frontal margin, the compound eyes large, pleotelson triangular, uropods have endopods not extending beyond the end of the pleotelson.

Occurrence of Vibrio parahaemolyticus and Staphylococcus aureus in seafood.

The objective of this study was to establish the occurrence of Vibrio parahaemolyticus and Staphylococcus aureus in several species of sea fish and mussels (Mytilus galloprovincialis). The study included a total of 33 samples of frozen sea fish and 64 samples of fresh wild and farmed mussels purchased from the stores. V. parahaemolyticus was isolated and confirmed via PCR in 2 (6%) fish samples (Atlantic cod and Alaska pollock) and 20 (31%) mussel samples. S. aureus was also isolated and confirmed via PCR in 2 (6%) fish samples (Argentine hake and Atlantic cod). Significant differences were found in the total bacterial contamination between wild mussels (6.54 log cfu/g) and farmed mussels (6.69 log cfu/g). Total V. parahaemolyticus count did not show significant differences either between wild (4.45 log cfu/g) and farmed mussels (4.99 log cfu/g). In wild mussels the S. aureus count was found to be 4.50 log cfu/g, while in farmed mussels it was 3.14 log cfu/g. The occurrence of V. parahaemolyticus and S. aureus in fish and mussels presents a risk to the consumer’s health.

Cytogenetic damage in native Baltic Sea fish species: environmental risks associated with chemical munition dumping in the Gotland Basin of the Baltic Sea.

This study represents the first attempt to assess genotoxicity and cytotoxicity effects in herring (Clupea harengus membras), flounder (Platichthys flesus), and cod (Gadus morhua callarias) caught at 47 study stations, located close to chemical munition dumpsites in the Gotland Basin, the Baltic Sea. Herring sampled from stations located in the center of chemical munition dumpsites exhibited the highest levels of micronuclei (MN) and total genotoxicity (ΣGentox), which is defined as the sum of frequencies of such nuclear abnormalities as micronuclei, nuclear buds, nuclear buds on the filament, and bi-nucleated erythrocytes with nucleoplasmic bridges. Exceptionally high and high ΣGentox risks were determined for flounder (89.47%), herring (79.31%), and cod (50%) caught at the stations located close to the chemical munition dumpsites.

Scrabbling around for understanding of natural mortality

The authors have collaborated for the past 40 years on a sequence of initiatives for a range of fisheries and marine ecosystems projects. These had natural mortality (M) as a common thread and have helped increase understanding of this elusive parameter. Here, we provide a reprise as well as an extension of our earlier results. Taken together, these help to develop an understanding of M of exploited fish stocks, particularly those of the North Sea. Firstly, a reprisal is given of the key findings about M due to predation by important fish stocks of the North Sea. Estimates were first produced by the ICES Multispecies Working Group using multispecies virtual population analysis (MSVPA) in combination with extensive stomach content data - collected for all four quarters and around the whole North Sea during 1981. Results from this initiative demonstrate that predation mortality (M2) represents a large portion of M for many North Sea fish species, but varies markedly both by age and by year, thus refuting the then widely adopted hypothesis that M was constant. Moreover, these variations were sufficiently large to overturn single species predictions of sustainable yield. M2 results from the 1980′s also indicated that mortality levels were related to prey size and species. The paper then reprises results from studies made by the private working group (PWG) that the authors formed to continue their collaboration. These focused first on size spectra of fish communities both by data analysis and by developing a simple trait-based model (cartoon) of the North Sea - the charmingly simple model (CSM). This modelling led to further questions about the basis of the coexistence of fish species in an ecosystem given that egg production scales approximately with asymptotic weight. This led to a plausible hypothesis that differential natural mortality rates are required that increase with the von Bertalanffy parameters of curvature K and asymptotic length L∞, but decrease with fish length. Data from the literature supported this hypothesis, which was further refined into canonical form: M=K(L∞/L)1.5. However, this hypothesis is also questioned because this form might not be compatible with the predicted and observable fact that size-spectra slopes become more negative with increased general levels of fishing. Clearly, changes in size spectra should cause changes in M2. Results of new modelling work are presented where the CSM is modified to include differential natural mortality rates by K and L∞. The results suggest that M responds both to general levels of fishing and the slope of the ensuing size spectrum. This suggests that a more general expression for predation mortality would be M2=α(F)K(L∞χ)(Lβ(F)), where χ is likely to be close to the 1.5 value used in the canonical form. The work thus provides a likely form for M2 but by no means a universally applicable formula. It remains a hypothesis needing to be tested and perhaps calibrated against data from the sea. Such calibrations might indeed point toward a universal formula for M2.

Causal links between North Sea fish biomass trends and seabed structure

Distinct areas of seabed, called seascapes, are known to shape benthic habitats and communities, yet little is known about the extent to which they affect the dynamics of marine fish populations. We explored the relationship between seascapes and trends in the biomass density of several North Sea fish species. We divided the North Sea into 10 seascapes using standardized methods. Time series of fish biomass density were derived from the North Sea International Bottom-Trawl Survey (NS-IBTS) and aggregated to the seascape level. We analysed the interdependencies between these time series using a causal association network and found independent biomass density trends between adjacent seascapes at a time interval of 0 yr in all species assessed. Long-term causal dependencies in biomass density occurred at time lags of 1-2 yr across different gradients of exchange: (1) both directions from North to South; (2) unidirectional, North-South; (3) unidirectional, South-North; (4) unidirectional, East-West; and (5) no clear direction. Our findings indicate that the separation in (a)biotic conditions between North Sea seascapes can represent relevant barriers to the processes determining the observed fish biomass density. We found that non-fusiform morphology and demersal habitat preferences best explained short-term causal dependencies. This combination is particular to the flatfish and ray species included in the present study. Contrarily, the movement of large, long-lived, benthopelagic species best explained long-term causal dependencies. Our work highlights how causal association networks can be used to study the temporal dependencies between spatial time series in ecology.

Estimation of Formaldehyde Contamination In Selected Sea Fish Species Sold In Ernakulam District of Kerala State

Estimation of Formaldehyde Contamination In Selected Sea Fish Species Sold In Ernakulam District of Kerala State

Zoogeographic patterns of Red Sea fishes – are they correlated to success in colonization of the Mediterranean via the Suez Canal?

ABSTRACT A total of 1217 fish species were analysed and the percentage of species in each of a number of zoogeographic patterns was calculated. An additional two categories, Atlanto-Mediterranean (anti-Lessepsian and mariculture escapees) and two cichlid species, were not included in our calculations. The present paper presents the division of the Red Sea indigenous ichthyofauna into the following categories: Red Sea endemic (15.1%), Red Sea and Oman, Aden, and Arabian Gulf (12.7%), Red Sea and Western Indian Ocean (8.6%), Red Sea and Indian Ocean (5.2%), Red Sea and Indo-Pacific (53.3%) and Red Sea and circumglobal (5.1%). The opening of the Suez Canal in 1869 resulted in a massive migration of Red Sea biota into the Mediterranean, among them 104 fish species. Several studies have attempted to determine whether there are traits that correlate with success in colonization of the Mediterranean by Red Sea fishes (Lessepsian migration). The results of our study demonstrate similar zoogeographic distribution patterns between the Red Sea ichthyofauna and those of the Lessepsian migrants. Thus, no correlation was found between wide-range distribution and success in colonization of the Mediterranean by Red Sea fish species, via the Suez Canal.