Rough Dab Hippoglossoides Platessoides Research Articles

Diet and trophic structure of fishes in the Barents Sea: between empty and full stomachs - large individual variability follows a common pattern.

More than 27,000 stomachs from 70 species of fish were collected from the Barents Sea in 2015. Quantitative stomach content expressed relative to the body weight of the predator fish (g g-1 as %) varied by four to five orders of magnitude for six species with the largest sample size (Atlantic cod Gadus morhua, haddock Melanogrammus aeglefinus, Greenland halibut Reinhardtius hippoglossoides, long rough dab Hippoglossoides platessoides, polar cod Boreogadus saida, and Atlantic capelin Mallotus villosus). The quantitative stomach contents of individual fish followed a common and strict statistical relationship for predator species or groups of species (by families), and for prey categories across predator species. The common pattern was log-normal-like and was modelled with good fit by different types of right-skewed distributions, that is, variants of the Box-Cox, generalized inverse Gaussian, inverse gamma, or gamma distributions. The long tail in the high end reflects high variation with no clear sign of a plateau, as could be expected from the concept of a "full stomach". This is interpreted to reflect that high stomach contents are rare events that are sampled at low frequencies. The maximum recorded stomach content varied from 1% to 34% of body weight for 55 species of fish, being positively correlated (R2 = 0.45) with sample size. About a third of the stomachs were empty, and the low tail of the log-normal-like distribution represents the transition to empty stomachs. The amount of food in the stomachs was overall low compared to maximum values, with mean and median of 2.0% and 1.1%, respectively, for the 17,873 stomachs containing food. Supported by bioenergetic considerations, this suggests relatively low feeding rates of the various fish predators but sufficient to meet their energy demands.

Digestive system of the marine blood fluke, Aporocotyle simplex (Odhner, 1900) (Digenea: Aporocotylidae) with consideration of the digenean digestive morphology

This is the first study describing the ultrastructure of the digestive system of a member of the marine teleost-infecting aporocotylid lineage, Aporocotyle simplex (Odhner, 1900), a blood parasite of the long rough dab Hippoglossoides platessoides (Fabricus, 1780) from the Norwegian Sea, Norway. The presence of particular morphological characters of the extensive A. simplex foregut and the four caecal ramifications are described. These show a syncytiality of the digestive epithelial lining with sunken perikarya in the foregut region and intraepithelial nuclei in the caecal region. Based on characteristic features of the pharyngeal muscle patterns in the Digenea, our results support the occurrence of a rudimentary pharynx in A. simplex. The short anterior esophageal portion retains tegumental cytoplasmic inclusions, but the middle-posterior esophageal portion shows considerable morphological modifications of the esophageal cytoplasm and sunken bodies modified into well-developed esophageal glands. These consist of undifferentiated cells, cells in different stages of differentiation and disintegrated cells, showing their renovation and apoptosis, controlled by the nervous system. Our data provide morphological evidence on the digestion of host erythrocytes within the lumen of the middle-posterior esophageal region. Morphological data indicated also the existence of the gastrodermal pathway, completing the digestive process. The revealed differences in the pharyngeal foregut region and in the caecal cytomorphology in marine A. simplex and the previously studied freshwater Sanguinicola inermis may support molecular data on the existence of divergent evolutionary lineages of marine and freshwater teleost-infecting species, or new data assigning Sanguinicola and Aporocotyle as separate families.

Detection of salmonid alphavirus RNA in wild marine fish: implications for the origins of salmon pancreas disease in aquaculture

Salmonid alphaviruses (SAVs), which include the aetiological agents of salmon pancreas disease (SPD) in farmed Atlantic salmon Salmo salar L. and sleeping disease (SD) in rainbow trout Oncorhynchus mykiss (Walbaum), are significant viral pathogens of European salmonid aquaculture. SAV is horizontally transmitted and the virus can survive for extended periods in seawater. A lack of convincing evidence for vertical transmission coupled to the fact that the SPD virus (SPDV) occurs in historically infected sites irrespective of fallow period duration suggests that a substantial reservoir of infection exists in the marine environment. We used a highly sensitive real-time PCR (qPCR) assay targeting a region of the SAV nsP1 gene to screen wild marine fish species for the presence of SAV in an attempt to identify such a potential reservoir. Screened fish species were caught in the vicinity of aquaculture activity in an area with a previous history of SAV infection (Shetland Isles, Scotland). SAV RNA was detected in internal organs (kidney and heart) from the flatfish species common dab Limanda limanda, long rough dab Hippoglossoides platessoides, and plaice Pleuronectes platessa. Based on these findings, sampling was extended to an area remote from aquaculture activity (Stonehaven Bay, NE coast of Scotland) from where heart tissues obtained from common dab also tested positive. While no virus could be cultivated from these samples, qPCR detections were shown to be SAV-specific by sequencing of an alternative gene region (E2) to that targeted by the qPCR assay. Analysis of these nucleotide sequences revealed minor differences to those previously obtained from farmed salmon, and subsequent phylogenetic analysis of an E2 dataset demonstrated a subtype V-like sequence.

Trypanosome infections of marine fish in the southern Barents Sea and the invasive red king crab Paralithodes camtschaticus

The red king crab Paralithodes camtschaticus was introduced to the Barents Sea from the North Pacific in the 1960s. A previous study concluded that it may be indirectly responsible for increased transmission of Trypanosoma murmanense to cod Gadus morhua in the southern Barents Sea by promoting an increase in the population of the leech vector Johanssonia arctica. Eleven species of fish, totalling 681 individuals, caught in October 2002 along the coast of Finnmark, were examined for trypanosome infections. The aims were to investigate changes in levels of infection in cod since 1999–2001, and to extend the sampling to other fish species. Relatively high infection levels were found in cod, haddock Melanogrammus aeglefinus and long rough dab Hippoglossoides platessoides, while other species were lightly infected or uninfected. In cod, no significant geographical differences in levels of infection were found, but haddock were significantly more heavily infected in western Finnmark.

Feeding habits of the Order Pleuronectiformes and its relation to the sediment type in the north Irish Sea

The diets of scaldfish Arnoglossus laterna, dab Limanda limanda, lemon sole Microstomus kitt, long rough dab Hippoglossoides platessoides, solenette Buglossidium luteum, thickback sole Microchirus variegatus, plaice Pleuronectes platessa, witch Glyptocephalus cynoglossus and Dover sole Solea solea in the Irish Sea were determined for March and October 1997 and 1998 and compared. Similarities in diets were examined using multivariate analyses. In general, there were differences in diet between species and generally the diets were similar within a species. Smaller individuals tended to have a similar diet. There were seasonal changes in the diets of individual species. Likewise, the overlap in diets between species changed between seasons and to a certain extent between sediment types.

The histopathology and ultrastructure of steatitis affecting common dab Limanda limanda

This study presents a new description, based on histopathological and ultrastructural studies, of a disease affecting the common dab Limanda limanda (L.). The condition can be recognised by the presence of multiple orange or yellow lesions in the pterygophorial region of the fish. The principal histopathological features are necrosis of fat cells, extensive macrophage infiltration leading to the formation of granulomatous structures, and the accumulation of lipopigment by lipid peroxidation. Based on this description, the condition has been diagnosed as steatitis. Although pathology associated with lipid peroxidation is the dominant characteristic of the lesions examined, it is proposed that this process is secondary to necrosis of the adipose tissue. The aetiology is discussed in the light of these observations. In addition, the first record of this condition affecting long rough dab Hippoglossoides platessoides (Fabricius) is made.

Isolation of viral haemorrhagic septicaemia virus (VHSV) from wild marine fish species in the Baltic Sea, Kattegat, Skagerrak and the North Sea

In order to analyse the occurrence of viral haemorrhagic septicaemia virus (VHSV) in the marine environment surrounding Denmark, fish tissue samples were collected on four cruises with the research vessel H/S Dana in 1996 and 1997. The sampling comprised 923 samples totalling 7344 fish representing 29 different species. VHSV was isolated from 24 fish samples from the Baltic Sea, four samples from Skagerrak and three samples from the North Sea. The virus-positive host species included herring Clupea harengus (11 isolates), sprat Sprattus sprattus (eight isolates), cod Gadus morhua (six isolates), rockling Rhinonemus cimbrius (one isolate), Norway pout Trisopterus esmarkii (one isolate), blue whiting Micromesistius poutassou (one isolate), whiting Merlangius merlangus (two isolates) and lesser argentine Argentina sphyraena (one isolate). VHSV has previously been reported from cod and herring, but not from the other five species. A virus belonging to serogroup II of the aquatic birnaviruses was isolated from three samples of flounder Platichthys flesus and three samples of dab Limanda limanda and a virus preliminary identified as iridovirus (lymphocystis virus) was isolated from seven samples of long rough dab Hippoglossoides platessoides.

Differences in life history features of long rough dab Hippoglossoides platessoides within Scottish waters

Recent studies have shown differences in life history features of long rough dab Hippoglossoides platessoides among populations of the North Atlantic. Here, length frequency distributions from commercial catches and age information from otolith readings are used to compare long rough dab from the North Sea and the West of Scotland. Catch data from the Scottish demersal fisheries show differences in the length distribution of long rough dab between the 2 areas, with large fish (>20 cm) more prevalent in the North Sea. The maximum length of long rough dab observed in commercial catches is 8 cm greater in the North Sea, where otolith readings indicate that the species has a greater longevity. Growth models suggest that long rough dab of age 3+ are significantly smaller in the West of Scotland. Potential explanations for the observed contrasts in hie history features include spatial differences in temperature-related metabolic costs, food availability, sex ratios (males tend to be smaller), or age-specific loss rates (emigration or mortality). Of these, we conclude that the hypothesis involving temperature-dependent metabolic costs is the least likely explanation.

Sealworm (Pseudoterranova decipiens) transmission to fish trawled from Hvaler, Oslofjord, Norway

Demersal fish were sampled over 3 years to describe sealworm Pseudoterranova decipiens infection levels in relation to the size of a local colony of common seals Phoca vitulina in Hvaler, Oslofjord, Norway. More than 2000 fish were examined for worms, and five fish species were found to be infected, cod Gadus morhua, four‐bearded rockling Enchelyopus cimbrius, plaice Pleuronectes platessa, long rough dab Hippoglossoides platessoides and dab Limanda limanda. A detailed analysis of worm accumulation in cod, the only infected species present in large enough numbers, shows a net decrease in worm transmission following the phocine distemper virus epizootic which killed two‐thirds of the seals in Hvaler in 1988.

The food and the feeding habits of the long rough dab, Hippoglossoides platessoides (fabricius 1780) in the north sea

The type and quantity of food, the feeding intensity as well as the diel feeding pattern of the long rough dab Hippoglossoides platessoides are described. The interaction of the species with the biological environment is also assessed. The North Sea long rough dab feeds throughout the year with a definite maximum from April till August when over 85% of the fish sampled were feeding. It feeds principally on crustaceans (natant decapods), polychaetes, and echinoderms (ophiuroids), but also consumes O-group whitting ( Merlangius merlangus), long rough dab, and gobies (Gobiidae) in the east-central North Sea nursery grounds during the summer months. The species does not complete strongly for food with the other three most abundant pleuronectids, viz. plaice ( Pleuronectes platessa), common dab ( Limanda limanda) and lemon sole ( Microstomus kitt), as shown by a comparison of major prey items in their stomachs and the anatomical structure of their digestive tracts. The differences in the diet between the North Sea population(s) of long rough dab and the population(s) of the species from other North Atlantic areas are probably a manifestation of ecological differences amongst these ecosystems, especially in the availability and the distribution of prey organisms.

On the morphology and life-history ofSterincotrema pagelli(Van Beneden, 1871) Odhner, 1911 andFellodistomum fellis(Olsson, 1868) Nicoll, 1909 [Syn.S. Ovacutum(Lebour, 1908) Yamaguti, 1953] (Trematoda, Fellodistomidae)

Abstract The cercaria of Steringotrema pagelli (Van Beneden, 1871) Odhner, 1911 develops in sporocysts in the bivalve Nucula nitidosa Winckworth and N. nucleus (L.). The cercaria has two long contractile tail furcae. The cercaria is swollowed by the final host, lemon sole Microstomus kitt (Walbaum) and dab Limanda limanda (L.). The life-cycle of S. ouacutum (Lebour, 1908) Yamaguti, 1953 is identical to that of Fellodistomum (ellis (Olsson, 1868) Nicoll, 1909 worked out in the Barents Sea. The furcocercous cercaria emerges from N. tenuis (Mont.) and is eaten by the brittle stars Ophiura albida Forbes, O. sarsi Lkt. and Amphiura chiajei Forbes. Catfish Anarhichas lupus L., long rough dab Hippoglossoides platessoides (Fabr.) and plaice Pleuronectes platessa L. are infested by eating the brittle stars. S. ovacutum is thus a synonym of F. fellis. The cercariae of S. pagelli and F. fellis are redescribed. The developmental stages of both species are described, based on stereoscan electron microscope observation...

The growth rate of the Long Rough Dab Hippoglossoides platessoides (Fabr.)—a correction

In a recent paper (Bagenal, 1955) on the growth rate of the Long Rough Dab Hippoglossoides platessoides (Fabr.) in the Clyde Sea area, a serious mistake was made.The ages of 1561 Long Rough Dabs, which were collected from October 1953 to September 1954, were determined from an examination of the otoliths, and from the age analysis each fish was allocated to a population f to a, de-pending on when it was supposed to have spawned. This procedure was designed to obviate the difficulty during the winter and spring when fish of the same year-class would be grouped differently according to the condition of the otolith edge.