Lepidopus Caudatus Research Articles

Opportunistic predatory feeding behaviour of Munida intermedia A. Milne-Edwards & Bouvier, 1899 targeting juveniles of Lepidopus caudatus (Euphrasen, 1788) in the north-western Mediterranean Sea

The genus Munida, inhabits various marine habitats and exhibits versatile feeding behaviour. This study explored the behavioural patterns of Munida intermedia, shedding light on its opportunistic behaviour and competitive interactions within its ecological niche. In 2018, during an investigation using a remotely operated vehicle (ROV), carried out on the Méjean shoal (north-western Mediterranean Sea), at 397 m depth, specimens were observed engaging in opportunistic predatory feeding, targeting juveniles of the bathypelagic silver scabbardfish Lepidopus caudatus. Our findings underscore the dynamic nature of M. intermedia feeding habits and the significant role of competitive interactions within its habitat, highlighting the role of video technology in capturing real-time information.

Seasonal variation of nutritional constituents in muscles of silver scabbard fish Lepidopus caudatus (Pisces: Trichiuridae) from Eastern coast of Tunisia

Seasonal variation in amino and fatty acids and mineral contents was investigated in 72 Lepidopus caudatus muscle fillets, averaging 803 ± 317 g in total wet weight and 110 ± 9.85 cm in total length, and collected from the Eastern coast of Tunisia, to give information on its nutritional constituents’ quality and determine the appropriate period for its consumption. Results showed significant differences in ash, moisture, crude protein, and total lipid content. Fatty acid composition varied significantly between the four seasons, with total PUFAs, predominated by docosahexaenoic acid, exhibiting high levels in spring, followed by total SFAs dominated by palmitic acid in spring and total MUFAs represented by oleic acid in autumn. Glutamic and aspartic acids showed high concentrations in autumn, with total essential amino acids and their non-essential acids ratio exhibiting a significant seasonal variation. Analysis of seasonal variation of minerals indicated that P revealed a high concentration in autumn, followed by K, Na, and Mg in summer and Ca in spring. The high quality of these nutritional constituents indicates the importance of L. caudatus muscle fillet as a source of energy and nutritional value throughout the year and thus can be added to the Tunisian food composition table.

Fish Nutrition at the Underwater Mountains of the Whale Ridge (Southeastern Atlantic). 3. Structure of Fish Accumulations and Fish Feeding

Pelagic accumulations of fish are formed above the underwater mountains of the Whale Ridge in the evening and at night, but not observed during daylight hours. The study of such an accumulation above one of the mountains reveals its structure. The central part of the cluster consists of splendid alfonsino Beryx splendens, silver scabbardfish Lepidopus caudatus and oilfish Ruvettus pretiosus tend to keep on the periphery of the splendid alfonsino accumulation. Previously, it was found that food of splendid alfonsino, silver scabbardfish, rosefish Helicolenus mouchezi, Richardson’s boarfish Pentaceros richardsoni, and Cape bonnetmouth Emmelichthys nitidus consisted of organisms forming sound-scattering layers (SSL) above the underwater mountains. The composition of food and the daily dynamics of feeding of the listed commercial fish species indicate that they use two feeding tactics. In the first case, rosefish, Richardson’s boarfish, and Cape bonnetmouth forage for most of their food during the day at the bottom, when the SSL-forming organisms descend to the top of the underwater mountain during the diel migration. In the second case, splendid alfonsino, silver scabbardfish, and oilfish as part of a structured pelagic aggregation feed at night on the organisms rising into the upper layers of the water and forming sound-scattering layers. This tactic expands the possibilities for feeding fish that form pelagic aggregations in the dark hours of the day and allows the use of organisms both brought by the current to the mountain top and those that descended here earlier during the diel migration and then stayed until the beginning of the evening.

Life History and Fishing Aspects of the Deep-Sea Silver Scabbardfish Lepidopus caudatus in the Azores.

Deep-sea fisheries are of important economic value. Therefore, it is necessary to generate biologically and ecologically based fishing plans to make this fishery sustainable over time. The silver scabbardfish, Lepidopus caudatus, is a worldwide-distributed demersal fish, commercially exploited in the Azores. Despite L. caudatus high landings and discharges in the region, information about its ecology, population structure, biology and fisheries remains little-known. This work analyzed scientific survey and fishery-dependent data from the past 30 years to understand the changes in abundance, spatial distribution and life history of this species. Lepidopus caudatus spatial distribution was associated with depths between 200 and 400 m, close to seamounts and islands, and on sandy bottoms. The size structure varied yearly, and the population was dominated by females (sex ratio, M:F = 0.46:1). Growth rates were between the estimated values in previous studies in the Azores and indicated a slow-grower species (L∞ = 171.62 cm, k = 0.12 year-1, Φ' = 3.52). The abundance indices highlighted a declining tendency, and this result was backed by the high exploitation rate for the fish in the region (E = 0.53). Lack of management measurements and the species' vulnerability could lead to the depletion of this species.

Analysis of Notifications of Rapid Alert System concerning Parasites in Fishery Products

Fish and fishery products are one of Morocco’s most important export products. Fish parasitism is a natural worldwide phenomenon. Fish parasites have a very wide distribution and are found in both the northern and the southern hemispheres of the globe. The present study aimed to assess parasitic infestation in fishery products by analyzing notifications available in the European rapid alert system for food and feed. The analysis involved 663 notifications registered from 2001 to 2019 on the grounds of parasitic infestation. For Morocco, 651 notifications concerning the different exported food products were analyzed. Among the 663 notifications for the presence of parasites, 161 (24.3%) were border rejections. A total number of 20 countries have been detected with the presence of parasites in their exported fish and fish products. The main fish species concerned with this hazard were Hake (26%), Silver Scabbardfish (10.5%), and Angler (9.3%). In Morocco, among the 651 notifications, 373 concerned with seafood (57.2%). The number of border rejections of fishery products was 220 that is 33.8% of overall notifications. Fish and fish products category are the most concerned with 170 rejections (26.1%), with 64 notifications due to the presence of parasites (37.6%). The Silver Scabbardfish was the species most affected by parasite infestations (23.5%), followed by European Anchovy (12.5%) and Swordfish (10.9%). In conclusion, the nematode Anisakis is the most common parasite in fish infestation while the plerocercoïd larvae of the Cestoda Gymnorhynchus gigas seems to have a predilection to infest the Atlantic Pomfret (Brama brama).

How Fishery Collapses: The Case of Lepidopus caudatus (Pisces: Trichiuridae) in the Strait of Sicily (Central Mediterranean)

The silver scabbardfish Lepidopus caudatus is a mesopelagic species living on the shelf and slope down to 600 m in temperate seas all around the world. In the Mediterranean, the species is caught mainly by longlines with a marked seasonality. In the early 90s in the Strait of Sicily (Central Mediterranean Sea), a new fishery targeting L. caudatus was developed. This fishery uses an ad hoc pelagic trawl gear called “spatolara.” Vessels using spatolara have increased from 1 in 1993 to 10 in 2007 with a growth of catches of up to 1,200 tons in 2011. Development of this fishery was not regulated by any specific management measures and, due to the progressive reduction of catch to 169 tons, only one vessel was active in 2018. The availability of catch and biomass indices from trawl survey since the beginning of trawling exploitation allowed providing the first assessment of the state of L. caudatus stock in the Central Mediterranean (GFCM Geographical Sub-Area 16) by using data-limited methods. Catch-Maximum Sustainable Yield (CMSY) and Bayesian State Space Schaefer model (BSM) were fitted to landings and abundance indices (2004–2018). The Abundance-Maximum Sustainable Yield model (AMSY) was also applied to survey data from 1994 (1 year after the start of the spatolara fishery) to 2018 to further corroborate the results. BSM prediction of biomass levels was just above 50% of BMSY, whereas AMSY estimated the current stock levels below 50% of BMSY. The BSM was used for forecasting B/BMSY and catches under different fishing scenarios. Although current exploitation was very close to FMSY, more than a decade would be needed to rebuild the stock to biomass levels producing MSY. A faster rebuilding could be achieved by fishing at least 80% of FMSY, with minimal loss in yield over the next 5–8 years. Following the development of a new fishery since the beginning, the study provides a further example of how unregulated exploitation leads to a heavy overfished state of stock and collapse of fishing activities.

First molecular detection of the parasites Molicola uncinatus and Hepatoxylon trichiuri (Cestoda: Trypanorhyncha) infecting the silver scabbardfish Lepidopus caudatus from the Central Mediterranean Sea: Implications for the seafood quality and safety

Trypanorhynch tapeworms are marine heteroxenous parasites, involving sharks and rays as definitive hosts, invertebrates (i.e. crustaceans) as first intermediate hosts, and various teleost fishes as intermediate/paratenic ones. The massive presence of Trypanorhyncha larval forms in the flesh or body cavity of the fish hosts reduces their market value, making them unappealing to consumers, or causing discards of fish products.The identification of merocercoids (N = 100) of Molicola uncinatus and plerocercoids (N = 46) of Hepatoxylon trichiuri parasitizing the silver scabbardfish, Lepidopus caudatus, from the Central Mediterranean Sea (off Malta coast), was obtained, for the first time, by using sequences analysis of the complete small subunit (ssrDNA) and the partial large subunit (lsrDNA) ribosomal RNA gene loci. The Bayesian Inference from the concatenated sequences obtained at the two gene loci showed that the individuals of M. uncinatus and H. trichiuri clustered, respectively, in two well distinct and supported phylogenetic lineages, corresponding to the two cestode species. High prevalence (P) and mean abundance (MA) values were observed in the infection with merocercoids of M. uncinatus (P = 100%, A = 28.81), with the ventral musculature of the silver scabbardfish as the most parasitized site. Plerocercoids of H. trichiuri were found to infect only the mesenteries, attached to various fish tissues, with a mean abundance rate of 1.28.Even if harmless to humans, a heavy parasitic load with larval stages of Trypanorhyncha, particularly in the edible part of the silver scabbardfish (as here reported for merocercoids of M. uncinatus), can compromise the appearance of the fish-food, making it repugnant and unappealing for the final consumer. It has been also discussed that when managing the risk related to parasites affecting the fish quality and safety of fisheries products, the fishing ground where the life cycle of those parasites takes place should be also taken into account, as it would include the ecological drivers of the infection with those parasites. This wider ecological approach would be of help to the Food Business Operators (FBOs), gathering knowledge useful to manage fisheries in a wide “One-Health” perspective, aware of sustainability, quality and consumer safety aspects of sea-food production.

Perfluoroalkyl substances associations with morphometric health indices in three fish species from differentially contaminated water bodies in Southeastern Brazil

Environmental perfluoroalkyl substance (PFAS) concentrations have increased in the last decades, although their behaviour in the environment and potential deleterious effects are still unclear. In this context, the present study aimed to assess potential associations among these compounds in three fish species from differentially contaminated areas in southeastern Brazil, and morphometric indices used to assess environmental exposure effects, Fulton’s condition factor (FCF), the Hepatossomatic index (HSI) and the weight to length scaling coefficient (SC). Fish samples were collected from three differentially contaminated study areas in the state of Rio de Janeiro, Brazil, Guanabara Bay (GB), the Paraíba do Sul River (PS) and the Rodrigo de Freitas Lagoon (RFL). Silver scabbardfish ( Lepidopus caudatus ) and whitemouth croaker ( Micropogonias furnieri ) were sampled from both the PS (N=5 scabbardfish and N=9 croaker) and GB (N=10 for both species), while mullet ( Mugil liza ) were sampled from GB (N=15) and RFL (N=10). Results indicate that some of the morphometric indices seem to be directly affected by PFAS contaminant trends. Significant differences (p<0.05) among FCF were observed for mullet and croaker, while significant HSI differences (p<0.05) were observed only for croaker. The SC for each fish population varied among sampling site and fish population and did not seem to follow a fixed trend, corroborating previous assessments. A discriminant canonical analysis demonstrated higher discriminating contributions for the FCF and two PFAS, namely PFDA and PFOA. This variation is probably due to differential PFAS accumulation reflecting differences in trophic levels, although no direct associations between individual PFAS and the assessed morphometric indices were noted. PFAS, however, comprise several compounds, and each may be a different contributor to deleterious physiological effects. Further assessments are required, to better understand the potential deleterious effects of these compounds on populational fish health status. • PFAS and morphometric fish health indices (FCF, HSI, SC) associations were assessed. • FCF and HSI are directly affected by PFAS contaminant levels at the different sites. • SC was not useful in determining differential contamination levels. • Higher DCA discriminating contributions were noted for FCF and for PFDA and PFOA. • No associations between individual PFAS and FCF, HSI and SC were observed.

Morphological analysis reveals the presence of Hepatoxylon trichiuri (Holten, 1802) Bosc, 1811 (Cestoda: Sphyriocephalidae) in Lepidopus caudatus (Euphrasen, 1788) (Pisces: Trichiuridae) from the Mediterranean Sea.

In this article, we report for the first time the presence of the parasite Hepatoxylon trichiuri in specimens of Lepidopus caudatus from the Mediterranean Sea. A total of four plerocercoids were studied using microscopy techniques for both morphological and histological analysis. RESEARCH HIGHLIGHTS: We report for the first time for the Mediterranean Sea the presence of the parasite Hepatoxylon trichiuri in specimens of the commercial fish species Lepidopus caudatus. The plerocercoids of H. trichiuri not seems cause observable illness in the fish. However, further studies are needed in order to better assess the incidence and prevalence of the parasite in L. caudatus and other fish species of commercial interest.

Mercury Detection in Benthic and Pelagic Fish Collected from Western Sicily (Southern Italy)

Simple SummaryIn highly polluted water, fish can accumulate Hg at concentrations that cause risk to human health. This has occurred in Sicily (Southern Italy), where there is activity from the petrochemical pole. In this paper, we present concentrations of mercury in 14 fish species collected from western Sicilian coasts in 2013. A significant difference was found between fish species examined but not between pelagic and benthic fish. Four out of 130 analyzed samples showed mercury concentrations over the European limits.In highly polluted water, fish can accumulate mercury up to a concentration of 10 mgKg−1. This has occurred on the eastern coasts of Sicily (Southern Italy), probably due to the intense industrial activity of this area. However, little is known about Hg accumulation in fish of the western Sicilian coasts. In this work, we examined the Hg accumulation of 108 fish samples belonging to 14 species collected from western Sicilian coasts using a direct mercury analyzer. The samples showed a mean mercury concentration of 0.165 ± 0.22 mg kg−1 with a maximum in Lepidopus caudatus (1.72 mgKg−1), exceeding the limits provided by EC Reg. 1881/2006. The lowest Hg levels were found in Sparus aurata samples (0.001 mgKg−1). A significant difference was found between the fish species examined (p < 0.05). The comparison between benthic and pelagic species did not show statistical differences (p < 0.05). Fish food constitutes the main route of Hg uptake for humans. Only four of the 130 samples examined reached a mercury concentration over the European limits. The comparative analysis of Hg pollution for benthic and pelagic species did not confirm a different trend in metal contamination.

Biomarkers of Exposure to Chemical Contamination in the Commercial Fish Species Lepidopus caudatus (Euphrasen, 1788): A Particular Focus on Plastic Additives.

In recent years, the Mediterranean Sea has become an accumulation zone for waste generated by the 22 countries bordering its shores. Although the effects of plastic litter on the marine environment and on organisms have recently been studied in other areas, further information is needed for the Mediterranean Sea and, in particular, about plastics additives inputs and interactions with the biota and the trophic network, such as phthalates and bisphenol A. Plastic material production, use and disposal contribute also to the release of heavy metals into the environment, such as mercury (Hg), often used during the production of chlorine, the primary ingredient in PVC, lead (Pb) and cadmium (Cd), which are used as stabilizers in PVC and leach out of products during use and disposal. Our research aims to evaluate phthalates, bisphenol A and heavy metals contamination in Lepidopus caudatus (Pisces, Trichiuridae), which could be considered as a potential sentinel species. For the evaluation of toxicological effects, we evaluated the expression of vitellogenin and metallothioneins 1. In all samples analyzed, we have not found microplastics in the gastrointestinal tract but chemical analysis revealed the presence of high content of phthalates, and in particular high quantities of DIDP, DEHP, bis-benzylester phthalate, bis-butyl ester phthalate and mono-N-butyl ester phthalate in different organs. Instead, trace elements detected in tissue revealed a trend of concentrations generally higher in liver and intestine than gill and muscle tissues. Immunohistochemical analysis for anti-metallothionein 1 antibody showed a strong positivity of liver cells, both in females and males. Analysis for the anti-vitellogenin antibody showed in females a strong positivity both in the liver cells and in the gonads, in male specimens was found to be always negative except for a specimen, in which it was highlighted a positivity in some areas of the liver and of the gonad.

Plastics occurrence in the gastrointestinal tract of Zeus faber and Lepidopus caudatus from the Tyrrhenian Sea

The present study investigates the occurrence of plastic pollution in two commercially important marine teleosts (Zeus faber and Lepidopus caudatus) from the northern coasts of Sicily (Tyrrhenian Sea). Plastics occurrence in the gastrointestinal tract was higher in Lepidopus caudatus (78.1%) than Zeus faber (51.4%). Debris characterization, carried out by micro-Raman spectroscopy, allowed identified the main types of found polymers as: polypropylene (PP), polyamide (PA), nylon and, to a lesser extent, polyethylene (PE). Of the two fish species studied, the silver scabbardfish appeared to be the more vulnerable to plastic ingestion. Our study represents a starting point that may pave the way for future investigation of the fate, accumulation and transfer of plastic debris to upper trophic levels, to verify their potential toxicity and to better understand strategies to mitigate this phenomenon.

Seasonal trend of Anisakidae infestation in South Mediterranean bluefish

A total of 1104 fish samples from markets of Sicily were analysed for the detection and species identification of Anisakidae nematodes. The preliminary analysis of the fish samples showed the presence of 2459 larvae. All the fish species revealed different prevalence of infestation, with a maximum of 100% for Lepidopus caudatus and a minimum of 4.5% in Sardina pilchardus. The 80% of the larvae examined by PCR-RFLP analysis belonged to Anisakis pegreffii species. The seasonal infestation trend of Anisakis was evaluated in all the fish sample examined. The results of the seasonal infestation trend showed a marked connection with the ecological aspects of the fish species examined. As far as we know, this work report for the first time important ecological aspects of Lepidopus caudatus specimens of South Mediterranean. This work could be useful to plan a seasonal fishing strategy aimed at reducing the health risks related to Anisakis.

Morphological and molecular identification of a new Kudoa thyrsites isolate in Mediterranean silver scabbardfish Lepidopus caudatus.

Myxozoans of the genus Kudoa (Myxosporea, Multivalvulida) infect marine and estuarine fish species worldwide. Some Kudoa species are of concern to the seafood industry since they may generate macroscopic cysts in the fish host's musculature, or cause post mortem myoliquefaction, commonly known as 'soft flesh'. One of the economically most important species is K. thyrsites, a myoliquefactive myxosporean parasite that occurs in many wild and cultured marine fish species worldwide. Here we identified a K. thyrsites isolate as the causative agent of myoliquefaction in silver scabbardfish Lepidopus caudatus from the Alboran Sea (western Mediterranean Sea). For comparative and validation purposes, the morphological and molecular characteristics of the isolate were compared with fresh spores of a K. thyrsites isolate infecting Atlantic mackerel Scomber scombrus from the Norwegian Sea. Myxospores of both isolates shared a stellate appearance and contained 4 unequal pyriform polar capsules (1 large, 1 small and 2 intermediate). These morphological traits were consistent with all other previously described K. thyrsites isolates. Moreover, the small subunit rDNA sequences of the Mediterranean and Norwegian Sea isolates revealed 100% similarity, and matched 100% with K. thyrsites isolates previously recorded in myoliquefactive Atlantic mackerel from the North Sea and off southern England. The findings suggest that K. thyrsites is the primary cause of myoliquefaction in silver scabbardfish from the Alboran Sea. This report represents the first morphological and molecular characterization of K. thyrsites in the Mediterranean Sea. A set of new allometric characters is proposed as additional descriptors for more accurate and specific description of kudoid myxospores.

Prey preferences and ontogenetic diet shift of European hake Merluccius merluccius (Linnaeus, 1758) in the central Mediterranean Sea

This study focuses on the ontogenetic diet change of European hake (Merluccius merluccius) in the north sector of the Strait of Sicily (SoS), central Mediterranean Sea. The species is one of the most important fish predators within the Mediterranean marine ecosystem and one of the main target species for local fisheries. A total of 2669 hake specimens between 7.5 and 67 cm of total length (TL) were collected in 2014–2015. The sample was divided into nine size classes and quantitative feeding indices were calculated for each size-class in order to analyse ontogenetic changes in prey preferences. Hierarchical cluster analysis and non-metric multidimensional scaling (nMDS) showed the occurrence of three main hake feeding guilds separated at 50% similarity. Euphausiids and mysids dominated the diet of hake smaller than 14 cm TL and crustacean decapods and fish were the main prey of hake between 14.5 cm to 17.5 cm TL. A shift toward pelagic and necto-benthic fish occurred over 18 cm TL: hake between 18 and 32 cm TL prey mostly upon Atlantic horse mackerel (Trachurus trachurus) whilst the silver scabbardfish (Lepidopus caudatus) was an important prey for hake over 32 cm TL. The study highlighted the key role played by the Atlantic horse mackerel for hake diet in the SoS, which is different to what has been previously observed in other Mediterranean areas where piscivorous hake feed substantially on small pelagic fish, such as anchovy and sardine. Information on hake diet composition, as provided in this study, can be integrated with data on consumption rate and population size to develop multispecies models leading to a quantitative understanding of the role of hake in the ecosystem.

Analysis of bycatch in the South African midwater trawl fishery for horse mackerel Trachurus capensis based on observer data

The South African midwater trawl fishery targets adult horse mackerel Trachurus capensis. The bulk of the catch is taken by a single freezer-trawler, the biggest fishing vessel operating in South African waters. As fishing takes place off the south coast in ecologically sensitive areas, there are concerns about the potential impacts of this fishing operation on non-target species. Fishing behaviour and bycatch of this fishery from 2004 to 2014 were investigated by analysing observer records with regard to catch composition, volume and temporal and spatial patterns. The midwater trawl fishery was estimated to have caught 25 415 tonnes annually, with a bycatch of 6.9% of the total catch, by weight. There are species overlaps with various fisheries, namely the demersal trawl, small-pelagic, line, shark longline and squid fisheries, yet the total bycatch estimates from this fishery are generally small relative to catches taken in the target fisheries. Bycatch species with the highest average annual catches were chub mackerel Scomber japonicus, redeye roundherring Etrumeus whiteheadi, ribbonfish Lepidopus caudatus and hake Merluccius spp. Large-fauna bycatch species included sunfish Mola mola as well as a number of CITES II- and IUCN-listed species, such as Cape fur seal Arctocephalus pusillus, dusky shark Carcharhinus obscurus, smooth hammerhead shark Sphyrna zygaena and thresher sharks Alopias spp. The 97.9% observer coverage is high and the 6.9% bycatch rate low compared to other South African fisheries; however, due to the large size of the individual hauls (average of 46.3 t), the average sampling rate of 1.56% is low. Our analyses suggest that bycatch in the South African midwater trawl fishery has been lower than in other South African fisheries and similar fisheries elsewhere, but due to the combination of high catch volumes and low sampling rates, estimation errors for rare species are high and there is a substantial risk of incidental unmonitored bycatch of rare large fauna and aggregations of small fauna. This could be mitigated by spatio-temporal management of this fishery, to avoid fishing in high-risk areas, and the introduction of an electronic monitoring programme.

A Comparison of Alternative Circle Hook (Kahle Hook) and J Style Hook Performance in Experimental Pelagic Longline Fishery in Turkey

In recent years, circle hooks have been encouraged as an alternative to traditional J-hooks in pelagic longline fisheries to minimize by-catch mortality and injury to sea turtles and other marine wildlife. Prior to this study, circle hooks had not been used by domestic commercial pelagic longliners in Turkey. The main objective of the study was to evaluate the efficiency of kahle hook comparing with J-style hook baited with sardine (Sardina pilchardus) in pelagic longline fishery in the Aegean coast of Turkey (Kuşadası Bay).We used conventional J-style hooks (Mustad 2315DT-4/0) and kahle hooks (Eagle Claw142A-6/0) for each fishing operation and compared catch rates, catch compositions of target and non-target species. The relative performance of kahle and traditional J-style hooks was tested during 22 valid pelagic longline fishing operations between August 2010 and December 2012. A total of 2200 hooks were used equally amongkahle and J-style hooks consecutively. Captured fish were identified, total and fork lengths were measured,weighed, the time of haulback, and hook type as well as by-catch fish were recorded. A total of 78 fish were caught belonging to 13 species during the samplings. The overall CPUE was 4.73 fishes per 100 hooks for kahle hooks and 2.46 fishes for J-style hooks. For the CPUE of all fishes, the difference was statistically significant (Z = -1.977; P&lt;0.05), in favour of the kahle hook being almost two times greater than the J-style hook. Likewise CPUE was 17007.69 g per 100 hooks for kahle style hooks and 4807.27 g for J-style hooks (Z = -1.997; P&lt;0.05). While no difference was found between two hook models on by-catch species, kahle hooks were more efficient in comparison to J hooks on discard species. Swordfish (Xiphiasgladius) had the highest CPUE (2.82) among all species for kahle hooks followed by silver scabbard fish (Lepidopuscaudatus), 0.64. For J-style hooks, silver scabbard fish catch had the highest CPUE (0.64) followed by swordfish (0.55).

Depuration of cadmium from blue mussel (Mytilus edulis) by hydrolysis peptides and chelating metal elements

The present experiment was conducted to investigate the effects of prepared hairtail (Lepidopusc audatus) hydrolysis peptide–metal element (Fe2+, Zn2+, Ca2+, or Mg2+) complexes (PH–Fe2+, PH–Zn2+, PH–Ca2+, or PH–Mg2+) on the depuration of cadmium (Cd) from blue mussel (Mytilus edulis) tissues. Cd concentrations in anterior adductor muscle, posterior adductor muscle, gill, mantle, and visceral mass of mussels were 11.391, 15.323, 63.672, 19.509, and 109.621μg/g, respectively, after 5days of exposure to 0.32mg/L Cd. Five groups of these exposed mussels were then exposed to seawater laced with four different concentrations of the peptide complexes listed above (5, 10, 15, and 20mg/L) for 8days. After 8days of depuration, 5mg/L of PH–Fe2+, PH–Zn2+, and PH–Ca2+ showed no significant (P>0.05) effects on Cd concentrations in mussel tissues. However, significant differences (P<0.05) were observed in groups exposed to 20mg/L of PH–Fe2+, PH–Zn2+, and PH–Ca2+. The Cd concentrations in anterior adductor muscle, posterior adductor muscle, gill, mantle, and visceral mass were significantly (P<0.05) decreased by 29.56–35.83%, 27.51–33.62%, 31.59–40.34%, 25.83–31.28%, and 33.62–33.97%, respectively. Nevertheless, the variables of Cd concentrations in tissues treated with 5–20mg/L PH–Mg2+ showed no significant (P>0.05) differences from controls at any point during the experimental period. For these reasons, PH–Fe2+, PH–Zn2+, and PH–Ca2+ can be recommended as depuration agents in mussel feed to decrease the Cd concentrations in tissues.

The role of silvery pout (Gadiculus argenteus) as forage prey in the Galician and Cantabrian Sea ecosystem (NE Atlantic) in the last two decades

Silvery pout (Gadiculus argenteus, Guichenot, 1850) is a very common and quite abundant species in Galicia and in the Cantabrian Sea, which plays an important role in the Cantabrian Sea ecosystem since it is one of the main trophic resources of many commercial species. In this study we analysed data obtained from a series of bottom trawl surveys carried out annually in autumn from 1990 to 2010 along the continental shelf of Galicia and the Cantabrian Sea. We examined the changes observed in the distribution patterns and abundance indices of this species and relate these with the occurrence and abundance of other commercial species in the area like hake (Merluccius merluccius), megrims (Lepidorhombus spp.) and blue whiting (Micromesistius poutassou). A significant correlation was found (R=0.45, p=0.038) between the abundance index of G. argenteus and hake, one of its main predator. A total of 137,780 stomachs of 19 most important predators were analysed during this period. The volume percentage (% V) of G. argenteus in the diet of some species was very high as it was the case of Lepidopus caudatus (94%) or Molva macrophthalma (58.2%). The frequency of occurrence (% FO) was important for these and other commercial species such as Lepidorhombus whiffiagonis (12.3%), Zeus faber (11.1%), Helicolenus dactylopterus (9.5%), Eutrigla gurnardus (8.6%), Lophius budegassa (8.9%) and M. merluccius (6.4%). There were evidences of density dependant feeding on G. argenteus. A significant correlation between G. argenteus yearly abundance in the stomachs of the assemblage of its 19 predators and survey abundance was observed (R=0.8977, p<0.01). Also, high correlation has been observed between the yearly survey biomass indices of G. argenteus and its % FO in the stomachs of hake, megrims and blue whiting for some length ranges of these predators. G. argenteus is an extremely important species in Galicia and Cantabrian Sea due to both its abundance in the ecosystem and its trophic role as forage species.

Gymnorhynchus gigas in Lepidopus caudatus (Actinopterygii: Perciformes: Trichiuridae): prevalence and related effects on fish quality

We evaluated the effects of Gymnorhynchus gigas on the freshness and hygienic quality of Lepidopus caudatus. Total Volatile Basic Nitrogen (TVB-N), Trimethylamine Nitrogen (TMA-N), as well as Specific Spoilage Organisms (SSOs) are the most important freshness indicators in fish. Our study was carried-out on 65&amp;nbsp;specimens of L. caudatus kept in ice and stored at 2&amp;deg;C for different period of time. The microbiological charge of SSOs recovered on a portion of parasitised muscles (MP) was compared with those recovered on portions of parasite-free muscles (M). The contents of TVB-N and TMA-N on MP, M, and G. gigas larva/ae were measured using the Conway microdiffusion method. High prevalence (72.31%) of G. gigas in the specimens of L. caudatus from the Mediterranean sea was observed. No statistically significant differences (P &amp;lt; 0.05) between M and MP were found during storage. However, massive infestation of G. gigas on the muscle of the silver scabbardfish could negatively influence TVB-N values, without compromising the sensorial characteristic of fish.