On the blood volume of the Mediterranean dogfish,Scyliorhinus canicula

The blood volume of the Mediterranean dogfish,Scyliorhinus canicula was determined to be 4.06±0.92 ml/100 g body weight. This result is discussed in relation with the dye dilution technique used, the degree of dye binding with circulating plasma proteins and the values and techniques used by other authors.     

Leiopathes glaberrima millennial forest from SW Sardinia as nursery ground for the small spotted catshark Scyliorhinus canicula

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A large tumour from the gray snapper, Lutjanus griseus (L.)

Abstract. Using a panel of special stains employed in human histopathology and immunohistology, the authors diagnosed a tumour from the common gray snapper, Lutjanus griseus (L.), as a myoma, Only a few such tumours have been previously reported from fishes. Gray snapper are readily available and may provide a model for basic studies on this, as well as other, types of tumour.     

Dietary inclusion of crystalline D- and L-methionine: effects on growth, feed and protein utilization, and digestibility in small and large Atlantic salmon (Salmon salar L.)

Use of crystalline methionine to optimize amino acid profiles in feeds for Atlantic salmon (Salmo salar L.) was studied in three experiments. A basic experimental diet with 25% of dietary protein from marine origin and the remaining 75% from soya protein concentrate was used either with or without supplementation of L ‐methionine, D ‐methionine or DL ‐methionine. A fishmeal‐based diet was used as control. In experiment 1, growth performance of 100 g salmon in seawater was improved by supplementation with the different methionine products. Growth performance was, however, inferior to that of fish fed the control. Feed conversion ratios (FCR) exhibited similar trends to specific growth rate (SGR) with methionine supplementation, but again not as the control. Protein retention, measured as productive protein value (PPV), was significantly better in the control and D ‐methionine groups as compared with either L ‐methionine or the nonsupplemented group. These trends were confirmed in experiment 2, using fish of the same size, where an absorption and digestibility study of D ‐ and L ‐methionine clearly indicated that D ‐methionine was absorbed as well as L ‐methionine. Results indicated that racemization of D ‐ into L ‐methionine occurs in liver and kidney in Atlantic salmon. Ornithine decarboxylase (ODC) activity in liver was significantly affected by dietary treatment and there was a good correlation with growth and feed utilization data. In experiment 3, a growth study with large salmon (1 kg) was performed using increasing supplementation of DL ‐methionine to the basic diet. Results indicated a methionine requirement for maximum growth of 9.2 g kg^–1 feed dry matter (DM) kg^–1 growth. This is slightly higher than that reported in the literature. The present study clearly shows that optimizing the amino acid profile by inclusion of a single crystalline amino acid (crystalline methionine) does not give the same protein utilization as that of a diet in which the amino acids are mainly protein bound. D ‐methionine was found to result in better protein utilization than L ‐methionine when measured as PPV.     

Spatial organisation of European eel (Anguilla anguilla L.) in a small catchment

Abstract –  Modelling-governing patterns of European eel ( Anguilla anguilla L.) distribution of four eel size classes (<150, 150–300, 300–450 and >450 mm) in the Frémur basin (northwest France) was done using artificial neural network (ANN) techniques and ecological profiles. Our results demonstrate the high predictive power of the ANN models. Some macro- and microscale factors, such as distance from the sea, depth and flow velocity, have the most significant influence on the models. Influence of distance from the sea appears to be very different from the spatial organisation usually described in river systems. In fact, the general tendencies of total eel densities according to the distance from the sea showed that densities increase weakly upstream. Another outcome was the variations in habitat preference according to the eel size, even if this species is spread over practically every type of microhabitat. Small eels were mainly found in shallow habitats with strong abundance of aquatic vegetation, whereas large eels tend to be found in intermediate to high depth with small to intermediate abundance of aquatic vegetation. Finally, we hypothesise that European eels change behaviour and microhabitat characteristic preference around a size of 300 mm.     

Seasonal changes in abundance and age structure of burbot Lota lota (L.) and stone loach Barbatula barbatula (L.) in the littoral zone of a large pre-alpine lake

Abstract – Seasonal changes in the abundance and age structure of the stone loach and burbot populations in the littoral of Lake Constance, Germany were examined. The abundance of both species was lowest during the summer months and highest during autumn. The stone loach population in the littoral comprised age classes 1 to 3 plus, in autumn, age class 0. The burbot population showed distinct seasonal changes in both length and age composition. During spring and summer, only age class 1 was present in the littoral whereas, in autumn, only age class 0 was caught. This remarkably strict habitat segregation of two age classes by season is discussed with respect to a possible mechanism for avoiding conspecific predator risk in a cannibalistic species.     

Lateral movement of common carp (Cyprinus carpio L.) in a large lowland river and floodplain

Abstract –  Common carp ( Cyprinus carpio L.) are a major freshwater invader and knowledge of their movements is important for planning control efforts. To investigate the movement patterns of common carp, radio-tags were implanted into 46 adult fish; 37 near a large floodplain wetland, the Barmah-Millewa forest, and 9 in the Murray River approximately 175 km upstream. Tagged fish were located every second week between August 1999 and March 2001. Common carp occupied total linear ranges (TLR) between 0.4 and 238 km (mean 30 ± 61 km), with 25 fish (62.5%) occupying a TLR < 10 km. Two fish made large distance movements approximately 650 km downstream. Fish sex, the number of locations, time at large, or tagging location explained little variability ( P  > 0.05) in TLR. Monthly distance from release varied from 0.04 to 238 km (mean 15 ± 44 km), and was not significantly related to river discharge and water temperature, but 29 of 31 (93.5%) fish tagged at Barmah moved from the Murray River into adjacent floodplain habitats upon flooding. Five fish (12.5%) moved large distances (>127 km) upstream of the Barmah-Millewa forest. Fourteen fish (35%) showed site fidelity to within 20 m and usually occupied one or two home sites. Twenty-six fish (65%) showed site fidelity to within 100 m occupying up to five sites during the study period. Movement patterns of common carp were complex, and individuals exhibited different strategies, which is typical of invasive species. Efforts to control and potentially reduce common carp populations in regulated river-floodplain environments should target key floodplain access points and over-wintering habitats to reduce adult biomass, spawning and recruitment levels.     

Glucose tolerance in turbot, Scophthalmus maximus (L.)

Eighty turbot, Scophthalmus maximus (L.), (average weight 61 g) were injected intraperitoneally with exactly 1 g glucose per kg body weight. There was a peak in plasma glucose 3 h post injection. Thereafter a gradual decrease to basal levels was seen within 24 h. Plasma triacylglycerol concentrations showed a rapid decline during the first 24 h, and thereafter stable values. Blood haematocrit values decreased from 20% before injection to 16% 72 h after injection. Liver glycogen concentrations showed an initial decrease from 8 to 5 g 100 g^?1 (w.w) during the first 12 h, and thereafter stable values, while muscle glycogen concentrations increased during the first 12 h, and thereafter showed a gradual decline until 72 h. This response was most probably caused by secondary changes upon handling in combination with the direct response to a glucose load. Thus turbot was able to restore alterations in carbohydrate metabolism efficiently within 24 h.     

Overwintering dormancy behaviour of the European eel (Anguilla anguilla L.) in a large lake

Overwintering dormancy behaviour was studied in female silver eels in Lake Mälaren in Sweden between 2008 and 2010. Depth choices and movements in relation to temperature were analysed from pressure and temperature records for 13 eels with implanted data storage tags, covering 17 overwintering periods and three intervening summer periods. Dormancy commenced in October–November as temperatures fell below 4–12 °C. Eels tended to remain motionless throughout the winter, with some short periods of activity signalled by small changes in depth distributions. During dormancy, the eel shows a clear avoidance of shallow areas <5 m in favour of the 10–25‐m‐depth interval. Activity tended to resume 4–6 months later in April–May as temperatures rose above 3–7 °C and ice cover broke, and eels spent more time at shallower depths of <5–10 m. The majority of the eels were assessed as being in the silver eel stage at the time of tagging. During the autumn months, the diving behaviour, with frequent and large vertical excursions and periods at the surface, was similar to that seen in migrating eels in the Baltic and Atlantic Ocean. In spring and summer, the behaviour differed, being dominated by more gradual depth variations, implying that the eels reverted from silver eel migration behaviour to yellow eel foraging behaviour. Body weight declined during dormancy, but other studies of starvation over comparable time periods showed significantly higher average specific weight losses, implying that the Mälaren silver eels must have fed between the end of dormancy and recapture.     

Ontogenetic changes of alpha-melanocyte-stimulating hormone (α-MSH)-like immunoreactivity in the brain and hypophysis of a scyliorhinid dogfish (Scyliorhinus torazame): An immunohistochemical study

Ontogenetic development of α-MSH-IR (alpha-melanocyte-stimulating hormone-like immunoreactivity) in the brain and hypophysis of a scyliorhinid dogfish (Scyliorhinus torazame) was studied immunohistochemically. α-MSH-IR first appeared in the hypothalamus of the brain in embryos at the 43-mm stage. Thereafter, α-MSH-positive cells and fibers gradually increased in number in mainly the tuberculum posterius of the hypothalamus during the embyonic periods. In the post-hatching juveniles at the 95-mm and 125-mm stages, α-MSH-positive structures in the brain were comparable to those in adult fish, although the distributional range of α-MSH-IR structures in the brain was less extensive than those in adult fish. In the hypophysis, α-MSH-positive cells first appeared in the caudal part of the adenohypophysis at the 54-mm stage, approximately coincident with the onset of pigmentation in the skin. During ontogenesis, the MSH-producing cells increased in number straightforwardly in the adenohypophysis. This revised version was published online in August 2006 with corrections to the Cover Date.     

Successful early weaning of Atlantic halibut (Hippoglossus hippoglossus L.) in small shallow raceway systems

Small raceways were used in a weaning experiment with Atlantic halibut (Hippoglossus hippoglossus L.) larvae. The size of the tanks was 1.0 × 0.4 m with a 1‐ to 2‐cm water level. Duplicate larval groups were transferred to the raceways from circular first feeding tanks at 0.07, 0.10 and 0.16 g wet weight, while recommended weaning size of this species is 0.2–0.3 g. During the first 7 days of weaning, Artemia was used as a food supplement in combination with the formulated dry feed. Thereafter only dry feed was used. The dry feed used in this experiment was produced by a special heat technique. The 0.07, 0.10 and 0.16 g larval groups were evaluated after 31, 25 and 17 days respectively (same date) The corresponding average survival was 81.4%, 78.0% and 96.6% and the specific daily growth rate was 3.18%, 3.17% and 2.38% respectively. In the Artemia control group, a survival rate of 96.0% and a growth rate of 5.28% was achieved. To evaluate the weaning success, the groups were followed in a 22‐day post‐weaning period on a commercial dry diet. Higher growth rates, 5.8–6.9%, were then obtained in all experimental groups, except control. The survival here averaged approximately 80% in the three experimental groups, but showed some differences between replicates. One hundred per cent survival was achieved during weaning in the former Artemia group. From the start of weaning to the end of the post‐weaning period, the survival rates averaged 64% for the 0.07 and 0.10 g groups, approximately 80% for the 0.16 g group and 96% in the Artemia control group. Higher variance (CV) through the experiment and highest growth of the 75% quartiles of the fish groups compared with the 50% and 25%, indicated suppressed growth of the smaller fish. The successful weaning at these small sizes considerably reduced the live food period. Based on the present knowledge of the energetic demands of this species, it is calculated that weaning at 0.07 g compared with 0.25 g will reduce the amount of Artemia needed by at least 60%. No differences in pigmentation or degree of completed eye migration were detected between groups, indicating that this is determined at earlier developmental stages.     

Resource partitioning between lake-dwelling Atlantic salmon (Salmo salar L.) parr, brown trout (Salmo trutta L.) and Arctic charr (Salvelinus alpinus (L.))

Abstract – Resource partitioning between Atlantic salmon parr, brown trout and Arctic charr was studied throughout the ice-free season in a north Norwegian lake. Juvenile salmon and trout (≤160 mm) utilized the littoral zone and juvenile charr the profundal, while adult trout and charr (>160 mm) were found in both. Juvenile salmon and trout had a similar diet, although trichopteran larvae were more important for the trout and chironomid pupae and three-spined sticklebacks for the salmon parr. Small salmon and trout parr (≤120 mm) had a higher diet overlap than larger parr (121–160 mm). The feeding habits of adult trout were similar to that of juvenile trout, but the former took larger prey items. At the population level, both salmon and trout were generalistic feeders with a broad diet, but at the individual level, both species had specialized on a single or a few prey categories. Juvenile charr were segregated from salmon and trout in both habitat and food utilization; they had a narrow diet consisting of chironomids and zooplankton, possibly reflecting their confinement to the profundal habitat which have a low diversity of potential prey. Larger charr also took zoobenthos and sticklebacks in the littoral zone. ^Note     

Insemination, fertilization and gamete management in tench, Tinca tinca (L.)

Various procedures for artificial insemination in tench, Tinca tinca (L.) were re-examined with evaluation of fecundity of males and females among different tench strains. The objectives of this study were to enhance fertilization and hatching rates through optimization of the activation solution, the insemination process, the activation of gametes, and the elimination of eggs stickiness. Sperm for all experiments was collected directly into immobilization solution of modified Kurokura solution containing 180 mM of NaCl and stored at 2 °C for 2.5–5 h prior to the experiment. When dechlorinated tap water was used for activation a gamete ratio of 1150 spermatozoa per egg showed the best significant fertilisation and hatching rates. Optimal ratio between eggs (weight in g) and activation solution (in cm³) was 1:1. Different concentrations of activation solutions such as NaCl from 0 to 68 mM (0–136 mOsmol kg⁻¹) without buffer statistically decreased fertilization and hatching rates. The activation solution containing 17 mM of NaCl, 10 mM Tris–HCl, pH 8 and 9 significantly increased fertilization and hatching rates compared to dechlorinated tap water of pH 7 or activation solution containing 17 mM of NaCl, 10 mM Tris–HCl, pH 6 and 7. Adhesiveness of the eggs was successfully removed by incubation in Alcalase and activity: 3.16 Anson units per cm³.     

Naturally occurring lesions and micro-organisms in two species of free-living sharks: the spiny dogfish, Squalus acanthias L., and the smooth dogfish, Mustelus canis (Mitchill), from the north-western Atlantic

Twenty-three smooth dogfish, Mustelus canis L., and 20 spiny dogfish, Squalus acanthias (Mitchill), were examined for the presence of diseases. Sharks were collected from the north-western Atlantic between April and September 2000. Major organs were sampled for histopathology and bacterial cultures were taken from kidneys. Macroscopic lesions were infrequent and included intestinal cestodiasis and gastric and dermal erosions. Microscopic lesions were common in both shark species. Mustelus canis had numerous degenerative lesions involving the pancreatic ducts, seminiferous tubules and coronary vessels. The most frequent lesions in S. acanthias were parasitic and included pancreatic nematodiasis and biliary myxosporeosis. Additionally, both species had focal meningitis, encephalitis, dermatitis, gastritis, enteritis and glomerulomesangial thickening. Microscopic parasites included intestinal coccidiosis, unclassified gastric and testicular protozoa, skeletal muscle and renal tubular myxosporeans, a branchial trichodinid ciliate, olfactory and branchial trematodes, gastrointestinal cestodes and larval nematodes. Shewanella putrefaciens , Photobacterium sp., Vibrio sp., Pseudomonas sp. and Alteromonas sp. were isolated from kidneys of nine sharks. The role of the above lesions in the natural mortality and morbidity of the two shark species is unknown. The finding that apparently healthy sharks can harbour potentially debilitating lesions warrants the inclusion of histopathological studies in the management and conservation of sharks.