bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of turbidity and illumination on the reaction distance and search time of the marine planktivore Gobiusculus flavescens
Authors: Utne A. C. W.
Published: April 2005

Both reduced illumination and increased turbidity caused a significant reduction in reaction distance of Gobiusculus flavescens. The longest reaction distance, 18.9 cm for larger prey (Calanus finmarchicus), occurred at a light level of 80 μmol m −2 s −1 compared to 12.9 cm for a smaller prey (Acartia clausi) at 8 μmol m−2 s−1. Above a light saturation level of 10 μmol m−2 s−1, additional light had little influence on reaction distance. In the turbidity experiments, the longest reaction distances were measured at turbidity levels of 10–20 JTU. Prey size influenced reaction distance at all tested light levels. Search time was influenced by prey size only at low illumination. With increasing turbidity, reaction distance to a group of prey was longer than to one prey.
The stomach of Oreochromis niloticus has three regions
Authors: Caceci T. , El‐Habback H. A. , Smith S. A. , Smith B. J.
Published: April 2005

The stomach of Oreochromis niloticus was divided into three distinct regions: initial, middle and terminal, corresponding roughly to the cardiac, fundic, and pyloric portions of the mammalian stomach. Grossly, the organ showed initial and terminal portions, the former connected to the distal part of the oesophagus and the latter to the proximal portion of the intestine. There was also a middle region, forming a large blind diverticulum communicating with the first two at their point of junction. The initial or cardiac region was shorter than the middle region but longer than the terminal one, and had a smooth surface devoid of gastric pits. The epithelium in this region was simple columnar devoid of goblet cells, with glandular regions in the lamina propria. The mucosa of the middle or fundic region had gastric pits lined by columnar epithelium, and simple tubular glands filled most of the lamina propria. The terminal or pyloric part of the stomach was very short and its mucosa was slightly folded and devoid of both gastric pits and mucous glandular cells. The lining epithelium of this portion of the stomach was simple columnar and a few goblet cells were seen at its junction with the first part of the intestine. The tunica muscularis of the stomach contained skeletal muscle in the initial and terminal regions, usually intermingled with smooth muscle fibres. Skeletal muscle fibres were also observed in the first portion of the small intestine, near the junction with the stomach.
Changes in the fatty acid profile of the Australian shortfin eel in relation to development
Authors: De Silva S. S. , Gunasekera R. M. , Collins R. , Ingram B. A. , Austin C. M.
Published: April 2005

In glass eels (54 mm TL; 0.018 g) of the Australian shortfin eel Anguilla australis the fatty acid composition was typical of marine species, with a n‐3 to n‐6 ratio of 5.3, a low level of mono saturated fatty acids (monoenes) and a high level of polyunsaturated fatty acids (PUFA). In elvers (pigmented: 56 mm TL; 0.028 g), the n‐3 to n‐6 ratio was 2.6. In elvers monoenes, as per cent of all identifiable fatty acids, increased to 30.9% from that of 19.8% in glass eels. The fatty acid composition of juvenile eels, reared from the original stock of glass eels and elvers, in outdoor, fertilized ponds, with (115 mmTL; 2.2 g) and without feeding (110 mmTL; 1.9 g), had a fatty acid composition typical of freshwater species, with a n‐3 to n‐6 ratio 1.9 and 1.3, and 37.7 and 46.5% of monoenes in unfed and fed groups respectively. A principal component analysis summarized efficiently the progressive changes in fatty acid composition from the glass eel to juvenile eel stage. The observed changes in the fatty acid of the different developmental stages in Australian shortfin eel are discussed in relation to physiological changes associated with the diadromous habit.
A study of the assimilation of fluorescent pigments of microalgae Isochrysis galbana by the early larval stages of turbot and herring
Authors: Tytler P. , Ireland J. , Murray L.
Published: April 2005

The appearance of large supranuclear vacuoles in the enterocytes of 1‐ and 4‐days post‐hatch larvae of turbot and herring, respectively, revealed by the pinocytotic uptake of a fluorescent marker (FITCdextran), indicates a potential for the absorption of dissolved nutrients by the endotrophic stages of marine fish larvae. Ingestion of algal cells by turbot larvae was observed soon after hatching, but low level pinocytotic absorption of algal material was first seen during the second day. More extensive lysis of algal cells and pinocytotic absorption occurred 24 h later. Although lysis of I. galbana was shown to occur at low external osmolarities, it is unlikely that sufficiently low osmolarities present in the hind gut of turbot larvae explained the observed rupture of algae. Other mechanisms for digestion are discussed. In newly hatched herring larvae, algal cells were unable to pass beyond the constriction in the mid‐gut caused by the yolk sac. When algal cells were eventually seen to pass into the hind gut, there was no evidence of algal digestion or absorption throughout the remaining endotrophic and early exotrophic stages of herring larvae, although pinocytosis was observed to occur mid‐way through the endotrophic stage.
Factors affecting the recognition of population‐specific odours by juvenile coho salmon*
Authors: Courtenay S. C. , Quinn T. P. , Dupuis H. M. C. , Groot C. , Larkin P. A.
Published: April 2005

Juvenile coho salmon Oncorhynchus kisutch from the Quinsam, Big Qualicum and Puntledge Rivers, British Columbia, Canada, discriminated between the chemical emanations of similarly aged salmon from their own and another population. However, common rearing during the embryonic, larval and early free‐swimming stages rendered families more attractive to each other than they were otherwise. Preference among populations was also influenced by quantity of odour produced by the fish. Some fish, notably the Quinsam River population, appeared to produce greater quantities of attractants than other fish. Finally, the salmon also preferred water conditioned by faeces of members of their own population over blank water and, in one of two experiments, over water conditioned by faeces of non‐population members, suggesting that at least some of the odourants mediating intraspecific discriminations are present in faeces. These results confirm earlier studies demonstrating that salmonid populations differ in odours distinguishable by conspecifics but indicate that experiments investigating this phenomenon must be designed carefully to avoid bias owing to differences other than population‐specific traits. The role of population recognition in the lives of salmonids is unclear; it might be a manifestation of more general imprinting for homing, of sibling recognition, or it might play a role in mate choice.
Environmental factors affecting migration of the European eel in the Rivers Severn and Avon, England
Authors: White E. M. , Knights B.
Published: April 2005

Studies were conducted during 1991–1993 on environmental factors affecting the upstream migration of eels in the Rivers Severn and Avon, England. Migrants (> 156 000 pigmented elvers and > 189 000 juveniles) were trapped as they attempted to ascend weir or sluice barriers. Multiple regression models were developed to compare catches per trap per night (C) with data for various key environmental parameters at seven sites, from the tidal limit to a maximum of 42.5 km upstream. The key stimulus for migration of both elvers and juveniles at the tidal limit was water temperature, with some weaker monthly influences related to seasonal temperature increases. Smaller annual influences probably related to earlier glass eel recruitment into the lower estuary. A weak early tidal effect was demonstrated only once, in 1993 in the Severn. Temperature also exerted significant effects on C of juvenile eels at the tidal limit and in the non‐tidal rivers, although effects weakened with distance upstream. Year, month, river flows and whether traps were mounted on weirs or sluices made only small contributions at a few sites. Distance between traps also contributed to combined data for upper Severn sites. The threshold temperature in all cases was 14–16°C, with low to zero catches below 10–11°C, catch maxima being achieved above 18–20°C. The implications of strong temperature‐dependence of migration in relation to stock recruitment and management are discussed. Special reference is made to recent decreases in recruitment of eels to Europe and N. America and possible long‐term effects of global warming.
Stomach contents of adult sea trout caught in six English rivers
Authors: Elliott J. M.
Published: April 2005

The probability of feeding was significantly lower (P<0.001) for male than for female sea trout in six rivers, and decreased significantly (P<0.05) for both sexes with increasing distance upstream from the normal tidal limit. The diet changed markedly from marine to freshwater and terrestrial foods with increasing distance upstream, especially among females.
Effects of temperature, hypoxia and activity on the metabolism of juvenile Atlantic cod
Authors: Schurmann H. , Steffensen J. F.
Published: April 2005

Standard metabolic rate (SMR), active metabolic rate (AMR) and critical oxygen saturation (Scrit) were measured in Atlantic cod Gadus morhua at 5, 10 and 15° C. The SMR was 35.5, 57.0 and 78.2 mg O2 kg−1 h−1 and Scrit was 16.5, 23.2 and 30.3%, at 5, 10 and 15° C, respectively. Previously reported SMR for Atlantic cod from arctic waters at 4° C was twice that measured at 5° C in the present study. A possible intraspecific latitudinal difference in the SMR is discussed. The AMR was 146.6, 197.9 and 200.4 mg O2 kg−1 h−1 and the critical swimming speed (Ucrit) was 1 6, 1.7 and 1.9 at 5, 10 and 15° C, respectively. The maximum oxygen consumption was found to be associated with exercise, rather than recovery from exercise as previously reported in another Study of Cod metabolism.
Predation by sprat and herring on pelagic fish eggs in a plaice spawning area in the Irish Sea
Authors: Ellis T. , Nash R. D. M.
Published: April 2005

Predation on planktonic fish eggs was examined by stomach content analysis of sprat and herring sampled in a plaice spawning area to the east of the Isle of Man in March 1993. Plankton samples were taken to examine prey selection. The clupeids showed a selection for the later developmental stages of plaice eggs. Plaice eggs had a refuge in size from predation by sprat <80 mm total length which selected smaller non‐plaice eggs. However, herring and sprat >80 mm total length showed a strong selection for plaice eggs, presumably due to their large size.
The ontogeny of the chondrocranium in Clarias gariepinus: trends in siluroids
Authors: Adriaens D. , Verraes W.
Published: April 2005

The ontogeny of the chondrocranium of 31 different stages of the African catfish Clarias gariepinus (Siluroidei: Clariidae) was studied, both from cleared and stained, and sectioned material. The fish ranged from 4.1 (1 day post‐hatching) to 127.0 mm SL (100 days post‐hatching). The chondrocranium of C. gariepinus seemed to correspond to the general adaptive trends in siluroids, especially in relation to the reduction of eye size and the dorso‐ventral flattening of the skull. The platybasic neurocranium involved several modifications related to the trabecular bars, the hypophyseal fenestra, the ethmoid region and even the olfactory nerves. Certain reductions were present, which have been observed in all siluroids (e.g. absence of the pila lateralis, the commissura lateralis, the myodomes) or are part of a variable trend within siluroids (e.g. reduction of the taenia marginalis anterior and the tectum synoticum). Compared with some other siluroid species, the neurocranium of C. gariepinus is well developed, for example in the otic region. The same was observed in the splanchnocranium where some general siluroid trends persist (e.g. isolation of palatine from pterygoquadrate, presence of ‘hyo‐symplectic‐pterygoquadrate’ plate). Some trends, as observed in other siluroids, were present also (e.g. interhyal continuous with suspensorium and ceratohyal, Meckel's cartilage initially continuous with the suspensorium). The branchial basket is well developed as all expected elements are present (basibranchials I‐IV, hypobranchials I‐IV, ceratobranchials I‐V, epibranchials I‐IV). Based on the observed ontogeny of C. gariepinus and data from the literature, a hypothesis was formulated which indicated the presence of a general reductional trend within siluroids. In C. gariepinus, all four (I‐IV) infrapharyngobranchials develop, although the anterior two are much reduced and fused with each other.
Field studies on the ureogenic gulf toadfish in a subtropical bay. I. Patterns of abundance, size composition and growth
Authors: Serafy J. E. , Hopkins T. E. , Walsh P. J.
Published: April 2005

Opsanus beta abundance in Biscayne Bay, Florida, varied significantly depending on site and season. O. beta catch per unit effort (cpue) was highest in southern study sites which tended to provide the combination of shallow mean depth, nocturnally high levels of dissolved oxygen, and Thalassia‐dominated substrate. Significant seasonal differences in abundance were restricted to the three sites where O. beta cpue tended to be highest; two of these sites shared the same pattern of in crease during the cool‐dry season (November‐April), followed by a return to lower levels during warm‐wet season (May‐September). Dramatic seasonal abundance increases could not be ascribed to large influxes of immature fish. Rather, size composition data suggested sexually mature individuals moved seasonally among habitats, possibly for reproductive purposes. Modal analysis of length‐frequency data followed by nonlinear regressions yielded preliminary values for the von Bertalanffy growth parameters K and t0, given that Lσ= 300 mm. Possible reasons for O. beta growing slower and attaining a smaller maximal size than its temperate congener, O. tau, are discussed.
Field studies on the ureogenic gulf toadfish, in a subtropical bay. II. Nitrogen excretion physiology
Authors: Hopkins T. E. , Serafy J. E. , Walshw P. J.
Published: April 2005

In order to examine the in situ nitrogen excretion physiology of gulf toadfish (Opsanus beta) (Fam. Batrachoididae), several biochemical and physiological measurements relating to urea synthesis and excretion were measured in samples taken from freshly collected gulf toadfish from a subtidal population in Biscayne Bay, Florida, U.S.A. This indirect appoach was used, instead of direct measurements of nitrogen excretion, because nitrogen excretion patterns of gulf toadfish are altered markedly during the first 24 h of capture disturbance or laboratory confinement. The values obtained for plasma cortisol levels, and the activities of hepatic ornithine‐urea cycle enzymes, including glutamine synthetase (and its partitioning between cytosolic and mitochondrial compartments), suggest that gulf toadfish in Biscayne Bay may excrete a substantial portion of their waste nitrogen as urea. Also conducted were correlation analyses of several biotic variables (plasma [cortisol], enzyme activities, plasma [urea], hepatosomatic index, and plasma [Ca++]) with several abiotic variables (temperature, salinity, depth and dissolved oxygen), and with collection site and season. Results of these analyses are discussed in the context of hypotheses to explain ureotely in this teleost fish.
Size‐selective predation by the cleaner fish Labroides dimidiatus
Authors: Grutter A. S.
Published: April 2005

A comparison of the size‐frequency distribution of parasitic gnathiid isopod larvae in the diet of the cleaner fish Labroides dimidiatus and on six host fish species (Chlorurus sordidus, Ctenochaetus striatus, Hemigymnus melapterus, Scolopsis bilineatus, Siganus doliatus, Thalassoma lunare) was made on one occasion. The comparison was repeated with Hemigymnus melapterus on three occasions and between two islands in Australia. L. dimidiatus selected larger gnathiids at all times at Lizard Island but not at Heron Island. Size‐selective predation by L. dimidiatus suggests any potential effect of cleaner fish on parasites may vary according to the size of parasite. However, this effect appears to vary spatially.
Computerized analysis of motility, motility patterns and motility parameters of spermatozoa of carp following short‐term storage of semen
Authors: Ravinder K. , Nasaruddin K. , Majumdar K. C. , Shivaji S.
Published: April 2005

A computer‐aided semen analysis system was used to assess the % motile cells following storage of carp semen in 11 different buffers at 2, 5 or 22° C. BWW and TLP were the most suitable storage buffers because carp semen stored at 5° C in these buffers following activation showed no significant decrease in % motile spermatozoa up to 24 h. But, in most of the other buffers (Fish Ringer, Cytomix, Cortland, FRT, Mannitol, FPS, NAS and TSM) the motility potential was lost by 2 h. Storage was best at pH 6–9 and at 5° C. Carp spermatozoa exhibit three distinct motility patterns, namely ‘linear’, ‘circular’ and ‘haphazard’, the proportion of spermatozoa with a particular motility pattern depending on storage buffer and time. All spermatozoa with a linear trajectory had high VSL, STR and LIN; those moving in circles had low VSL, STR, LIN and BCF and those with a haphazard trajectory were distinct in that they had the highest ALH and their VSL, STR, LIN and BCF were higher than the circular moving spermatozoa and lower than the spermatozoa exhibiting linear trajectory. The study also demonstrates a pronounced time‐dependent decrease in VCL, VAP, VSL and ALH of carp spermatozoa following activation with water or low osmolality solutions. This study provides for the first time data related to seven motility parameters of carp spermatozoa and demonstrates how these parameter values could be used to evaluate quality of carp milt following storage in different buffers. It confirms that carp spermatozoa exhibit linear or circular trajectories and provides evidence for a third type of trajectory described as haphazard. All three motility patterns could be discriminated objectively on the seven motility parameters.
Intraspecific phylogeography of the Cape galaxias from South Africa: evidence from mitochondrial DNA sequences
Authors: Waters J. M. , Cambray J. A.
Published: April 2005

Mitochondrial cytochrome b gene sequences were obtained from representatives of five populations of the Cape galaxias Galaxias zebratus. Four highly distinct genotypes were revealed, with sequence divergence values ranging from 5.8 to 13.8%. Some of the pairwise divergences are the highest yet reported for cytochrome b within a fish species, and are more typical of interspecific and intergeneric comparisons. In contrast, the low genetic divergence (0.3%) between two recently recorded populations from the Krom and Gamtoos (Kouga) Rivers indicates recent gene flow. Parsimony analysis consistently produced a tree with the population from the Olifants River on the west coast as ancestral and eastern populations as progressively more derived. Estimated divergence times for the Olifants population range from 4.4 to 6.6 million years ago. The findings suggest that another detailed revision is required to determine whether these divergent populations represent a single species or a species complex.
Lipid and fatty acid composition of muscle and internal organs from Ruvettus pretiosus
Authors: Ruiz‐Gutierrez V. , Perez‐Zarza M. C. , Muriana F. J. G. , Bravo L.
Published: April 2005

The lipid composition of different muscular areas (dorsal, ventral, subcutaneous, periosteum) and organs (liver, gall bladder, testes) of a gempylid fish Ruvettus pretiosus was examined. Waxes were the main lipid fraction in muscular areas, while the liver and testes were quite enriched in triglycerides and phospholipids. Oleic acid and fatty acids of n‐3 family were the most frequently found in total lipids.
The effects of temperature and hyperoxia on arterial PO2 and acid‐base status in Piaractus mesopotamicus
Authors: Soncini R. , Glass M. L.
Published: April 2005

The effects of hyperoxia and change of temperature (range 20–30° C) on blood gases were studied in the teleost fish Piaractus mesopotamicus, native to several major river systems in Brazil. Large hyperoxia‐induced increases of arterial Po2 (Pao2) indicated that true branchial blood shunts are negligible in relation to total gill perfusion. This implies that blood gases will be influenced by ventilation rather than by shunts. Acute variations of temperature (t) were accompanied by changes of arterial blood pH (on the average ΔpHaΔt−1 of — 0·015 units °C−1), due mainly to alterations of Paco2: 2·4 mmHg at 20° C, 5·0 mmHg at 30° C. Concomitantly, Pao2 declined from 116 mmHg (20° C) to 89 mmHg (30° C). The data suggest that temperature‐induced changes of acid‐base status depend mainly on gill ventilation and that the decrease of Pao2 with higher temperature is a result of this regulation.
Spatial and foraging behaviour, diet and morphogenesis of postlarvae and juveniles of Pempheris vanicolensis in the Gulf of Aqaba, Red Sea
Authors: Fishelson L. , Sharon O.
Published: April 2005

Post‐settlement ecology, ontogenesis of morphology and behaviour were studied in juvenile Pempheris vanicolensis (Pempheridae, Teleostei) in the Gulf of Aqaba, Red Sea. Postflexion larvae of 5.6‐6.0 mm total length settled around breakwater heads and natural rocky outcrops of the subtidal zone, widely separated from adults dwelling in groups in coral reef crevices and caves. Settling juveniles formed groups of uniform age and foraged on zooplankton around their habitats. Their circadian behaviour was regulated by levels of illumination in the water, differing slightly in the various age groups. At sunset, juvenile P. vanicolensis migrated and dispersed in deeper water, returning before sunrise to their rocky habitats. Their patterns of foraging and migration behaviours were analysed. At 28.0‐32.0 mm total length and 500 mg body weight, the increase in height and length (H/L ratio) of the juvenile changed from monoto heterochronous, after which a rhomboid body shape, typical for this species, was formed. Concomitantly, the retina of the juvenile changed from a photopic to a scotopic one, the body became heavily pigmented, and the fish left the subtidal rocks, migrating to crevices in coral formations where they settled in close proximity to groups of adult P. vanicolensis.
Acid phosphatases of Esox lucius: tissue distribution and partial characterization
Authors: Panara F.
Published: April 2005

The presence of different acid phosphatase classes was examined in organs and tissues of the fish Esox lucius. The enzymes were separated by Sephadex G‐200 column chromatography, and characterized as regards tissue distribution, molecular weight, metal ion activation, inhibition, pH optima, temperature sensitivity, rate of hydrolysis and substrate specificity. High and low molecular weight acid phosphatases as well as high and low molecular weight Zn2+‐dependent acid phosphatases were present in pike organs and tissues. In addition, their biochemical properties and tissue distribution are very similar to that of respective bird and mammalian enzymes.
Phylogenetic investigations on the haplochromine Cichlidae of Lake Kivu (East Africa), based on lepidological characters*
Authors: Lippitsch E.
Published: April 2005

The phylogeny of the haplochromine cichlids of Lake Kivu was studied using lepidological characters. Only one species, Haplochromis astatodon was found to have a closer relationship to a group outside Lake Kivu, namely Haplochromis sensu stricto. The other 14 species form a monophyletic lineage that is part of a subdivision in the large Lake Victoria‐Edward‐Kivu flock. The internal phylogeny of this lineage was resolved to the species level.
Effect of river regulation on the life‐history patterns of Barbus sclateri in the Segura river basin (south‐east Spain)
Authors: Del Mar Torralva M. , Angeles Puig M. , Fernández‐delgado C.
Published: April 2005

The age structure, growth and reproduction of Barbus sclateri in a non‐regulated section of the Segura River were similar to previously studied populations of undisturbed areas. Differences in the duration of the growth period or the reproductive cycle are considered evidence of the plasticity of the species as it adapts to different latitudes and local habitat characteristics. However, this population differed from one in a section with artificial water flow regulation. The non‐regulated river population had a greater number of age groups, displayed a regular condition cycle, reached maturity earlier at lower ages and lengths and showed greater fecundity than the regulated river population. The mean lengths at age were longer in the regulated river population, possibly owing to the longer river section studied and/or to selective mortality of smaller specimens within a particular age group from the high water velocity when sluices are opened.
The reproductive biology of Scyliorhinus canicula in the Bristol Channel, U.K.
Authors: Ellis J. R. , Shackley S. E.
Published: April 2005

Among 972 Scyliorhinus canicula, the overall sex ratio (males:females) was 1:1·23. Males matured between 490 and 540 mm LT with 50% maturity at 520 mm. Females matured between 520 and 640 mm LT with 50% maturity at 550 mm. Female gonadosomatic index peaked in May. Fecundity increased with fish length. The egg laying season lasted 10 months with a peak in June and July. The importance of erect, sessile invertebrates such as bryozoans, poriferans and hydroids as egg‐case deposition sites has been established. Recently hatched fish were born in an equal sex ratio and at a mean length of 100·5 mm and mean weight of 3·07 g. One intersexual fish is described.
Interhabitat migration of juvenile Atlantic salmon in a Newfoundland river system, Canada
Authors: Erekinaro J. , Gibson R. J.
Published: April 2005

Migrations of juvenile Atlantic salmon between habitats (both fluvial and lacustrine) were studied in a Newfoundland river system from May through September. Salmon parr showed poor site fidelity in fluvial habitats, and high rates of migration, especially in spring‐early summer. Most habitat shifts were upstream from fluvial habitats to a lake at the head of a small tributary. In September, 10% of the salmon parr caught in the lake (n=275) had been marked in the main stem of the river or in the tributary stream (total n=641). The abundance of parr in the lake increased in May‐June, then declined gradually to September. Most of the lacustrine immigrants were 1+ parr. Mature males were found amongst the autumnal emigrants. Salmon parr in the lake grew larger than those in the river, and lacustrine smolts captured in the lake were larger than those caught at the mouth of the river.
The cryptic responses of hatchery‐reared sole to a natural sand substratum
Authors: Ellis T. , Hoowell B. R. , Hughes R. N.
Published: April 2005

In laboratory experiments, both reared and wild sole Solea solea selected a sand substratum in preference to a hard substratum. Reared sole with no previous experience of sand buried quickly when placed on sand. Light motivated burial, and the motivation of reared sole to bury was as strong as that of wild sole. The burial efficiency (the proportion of the ocular side covered by sand after a single burial attempt) of reared sole was lower than that of wild sole, but increased to that of wild sole after a period of 12 days maintenance on sand. Motivation to bury is therefore innate, but efficiency is affected by experience. The reactive distance of reared sole to a standardized predation threat was the same as that of wild sole and was shorter when buried (6 cm) than when not buried (15 cm). Burial therefore affected the response to a predation threat, indicating that burial is a cryptic behaviour. Munsell colour charts were used to determine the time required for reared sole to match the skin colour ‘tone’ of wild sole after placement on sand. Adaptation of colour value (lightness) took 4–7 days, but adaptation of chroma (intensity of colour) and hue took 33 and 69 days respectively. It is therefore recommended that flatfishes reared for stock enhancement exercises are conditioned to sand prior to release due to the relatively long time required for crypsis to improve through colour adaptation and burying.
The use of drop traps to estimate the efficiency of two beam trawls commonly used for sampling juvenile flatfishes
Authors: Wennhage H. , Gibson R. N. , Robb L.
Published: April 2005

The efficiencies of a 2‐m and a 1·5‐m beam trawl for catching newly settled flatfish and brown shrimp were compared with that of a 1‐m2 drop trap that was assumed to be 100% effective. Low and variable trawl efficiencies were recorded but the trawls were not size selective within the size range of individuals captured.
Inherited differences in head allometry in polymorphic Arctic charr from Loch Rannoch, Scotland
Authors: Adams C. E. , Huntingford F. A.
Published: April 2005

Planktivorous and benthivorous morphs of wild Arctic charr Salelinus alpinus from Loch Rannoch, Perthshire, Scotland, reared in the laboratory from artificially fertilized eggs under identical conditions, were morphologically distinct (based on a series of head measurements) from an early age. For some morphometric characters, these differences became more marked with increasing body size, reflecting differences in the allometric growth patterns of the two forms. These data show that the observed phenotypic differences between these two trophic variants were, to some extent at least, inherited. Thus it is concluded that the mechanisms regulating expression of phenotype in the sympatric morphs of Loch Rannoch are significantly different from the environmentally determined body size polymorphisms reported from Norway but are closer to the more completely divergent forms from Thingvalavatn, Iceland.
Male reproductive strategy and reserve allocation in sand smelt from brackish lagoons of southern France
Authors: Tomasini J. A. , Laugier T.
Published: April 2005

In male sand smelt Atherina boyeri, from three coastal brackish lagoons of southern France, the duration of the reproductive season differed according to fish size: larger fish exhibited an extended reproductive season from February to August while smaller males reproduced only from April to June‐July. Smaller and larger fish showed differences in their seasonal pattern of reserves. Through the cold season, energy content was exhausted for over‐winter maintenance and reproductive needs, and was restored just after fish ceased reproducing. In smaller fish, however, reserves were more rapidly restored than in larger fish, and exhibited a decrease in autumn. This result suggested that small fish invested their energy into growth and winter survival rather than reproduction while older fish invested in reproduction. These results are discussed in terms of life history Strategies.
Semen from rainbow trout produced using cryopreserved spermatozoa is more suitable for cryopreservation
Authors: Babiak I. , Glogowski J. , Dobosz S. , Kuzminki H. , Goryczko K.
Published: April 2005

Oocytes from three female rainbow trout Oncorhynchus mykiss were inseminated separately with untreated or cryopreserved semen, which had been produced using either untreated (three males) or cryopreserved (three males) spermatozoa. In half of variants, the cryopreservation did not significantly affect fertilization efficiency. Regardless of whether the sperm donors were produced from cryopreserved or intact semen, insemination of oocytes with their intact sperm resulted in the same percentage of eyed embryos (94.4 and 94.3%, respectively). When eggs were inseminated with cryopreserved semen, the use of sperm from males produced with cryopreserved spermatozoa resulted in a significantly higher percentage of eyed eggs than in case of donors produced with intact sperm (89.6 and 81.7%, respectively). The production of rainbow trout using cryopreserved sperm does not appear to negatively affect reproductive abilities of male progeny and semen from donors, which were produced using cryopreserved sperm, is more suitable for cryopreservation than the semen from donors produced with intactspermatozoa.
Cutaneous taste buds in gadoid fishes
Authors: Harvey R. , Batty R. S.
Published: April 2005

Cutaneous taste buds occurred on the head and fins in five species of juvenile gadoid fishes from the west of Scotland, but there were significant differences in their density between regions on the fish and between species for individual regions. The highest taste bud densities were recorded on the edge of the anterior naris flap, the barbel, pelvic fin rays, snout tip and upper lip. Cod Gadus morhua and poor cod Trisopterus minutus had significantly higher taste bud densities on the first two pelvic fin rays than the other species. This appears to correspond with their more benthic lifestyle, in which the pelvic fins are frequently trailed over the sea bed when searching for prey.
17α,20β,21‐Trihydroxy‐4‐pregnen‐3‐one: the probable maturation‐inducing steroid of the Lusitanian toadfish
Authors: Modesto T. , Canário A. V. M.
Published: April 2005

17,20β,21‐Trihydroxy‐4‐pregnen‐3‐one (17,20β,21‐P) was identified as the major metabolite of incubations of Lusitanian toadfish Halobatrachus didactylus ovarian follicles with [3H]‐17hydroxyprogesterone. The potency of several steroids in inducing germinal vesicle breakdown of follicle‐enclosed oocytes of Lusitanian toadfish was systematically examined by using an in vitro germinal vesicle breakdown (GVBD) bioassay. 17,20β‐Dihydroxy‐4‐pregnen‐3‐one (17,20β‐P) and 17,20β,21‐P, two confirmed maturation‐inducing steroids (MIS) in teleosts, were the most potent in inducing GVBD with ED50s ranging between 9 and 271 nM. Structure‐activity relationships followed similar patterns to what has been observed in similar bioassays, i.e. a vital requirement for 17‐ and 20β‐hydroxyl groups in C21 steroids and a reduction in activity of 14 and 5–6%, respectively, for 5‐pregnene and 5β‐pregnanes compared to 4‐pregnenes. Corticosteroids, testosterone and 17β‐oestradiol were ineffective. Folliculated oocytes stimulated by pituitary homogenate produced 17,20β,21‐P from endogenous substrates in amounts one order of magnitude higher than 17,20β‐P. These results strongly support the hypothesis that 17,20β,21‐P is the likely MIS in this species.
Traits of brown trout prey in relation to habitat characteristics and benthic invertebrate communities
Authors: De Crespin De Billy V. , Usseglio‐Polatera P.
Published: April 2005

A trait database based on habitat, behavioural and morphological characteristics of invertebrates enabled invertebrates known to have differential vulnerability to salmonid predation to be discriminated. Among all of these traits the most important were associated with invertebrate spatial proximity to salmonids (macrohabitat preference), potential conspicuousness and accessibility (e.g. flow exposure, mobility, tendency to drift, trajectory and agility) and handling efficiency (body flexibility and size). Data on benthos assemblages and brown trout salmo trutta diets collected over two consecutive summers in different macrohabitat types (e.g. pools, runs and riffles) of two Pyrenean streams demonstrated that: (i) decrease in torrential flow characteristics of habitats was associated with changes in invertebrate body shape and movement, and a decrease in body flexibility and tendency to drift; (ii) brown trout tended to feed on the most vulnerable invertebrates (e.g. those living in exposed microhabitats and with a high tendency to drift, agility and aggregation), except in faster flowing habitats. The results suggest that the potential vulnerability of benthic invertebrates increased with increases in flow (torrential) characteristics. Also, the database compiled on traits explained differences among brown trout diets, especially in slow flowing areas.
Experimental manipulation of male eggspots demonstrates female preference for one large spot in Pseudotvopheus lombavdoi
Authors: Couldridge V. C. K.
Published: April 2005

Females of the Lake Malawi cichlid Pseudotropheus lombardoi preferred males with one eggspot, the natural number, on their anal fin compared to males with two eggspots which had been artificially manipulated in number. Furthermore by manipulating the size of the eggspot. it was found that females preferred males with one large eggspot to males with one small eggspot. These results indicate that female preferences are responsible for the single eggspot in P. lombardoi and that this may be linked to species recognition as females of closely related species appear to exhibit different preferences for male eggspots.
Assimilation of different cyanobacteria as food and the consequences for internal energy stores of juvenile roach
Authors: Kamjunke N. , Mendonca R. , Hardewig I. , Mehner T.
Published: April 2005

Juvenile roach Rutilus rutilus fed on the cyanobacterium Aphanizomenon were able to maintain liver glycogen and muscle protein concentrations. In contrast, internal energy stores of fish fed on the cyanobacterium Microcystis were degraded. Liver glycogen, however, was higher than in starved fish, suggesting that roach was able to obtain some nutrients (probably carbohydrates) from the mucus cover of Microcystis. Weak assimilation of radiolabeled Microcystis by roach was detectable, and assimilation rates increased with increasing proportion of Aphanizomenon in a mixture of both cyanobacteria. It is concluded that the incomplete digestion of Microcystis was the main reason for the negative growth rates of roach when fed on this cyanobacterium species.
On the occurrence of Hippocampus fuscus in the eastern Mediterranean
Authors: Golani D. , Fine M.
Published: April 2005

The western Indian Ocean seahorse Hippocampus fuscus is recorded for the first time in the Mediterranean. Its presence there is probably due to migration from the Red Sea via the Suez Canal.
Genetic stock structure of bigeye tuna in the Indian Ocean using mitochondrial DNA and microsatellites
Authors: Appleyard S. A. , Ward R. D. , Grewe P. M.
Published: April 2005

Genetic differentiation was minimal and overall non‐significant among five collections of bigeye tuna Thunnus obesus from the Indian Ocean, examined for variation at mitochondrial DNA (mtDNA) and at seven microsatellite loci.
Effects of different food restrictions on somatic and otolith growth in Nile tilapia reared under controlled conditions
Authors: Massou A. M. , Panfili J. , Laë R. , Baroiller J. F. , Mikolasek O. , Fontenelle G. , Le Bail P.‐Y.
Published: April 2005

.Nile tilapia Oreochromis niloticus, initial age 12 days, were given an unrestricted (NR) or restricted (R) ration over 93 days which resulted in fish of very different sizes although the body condition factor (K) and the viscero‐somatic index (IV) remained almost unchanged. In a second stage (64 days) each group (NR & R) was divided into three subgroups that were subjected to 0 (NR0, R0), 15 (NR15, R15) and 30 (NR30, R30) days of food restriction, respectively. The impact of the different treatments on the somatic growth during the second stage of the experiment had an effect, with a highly significant difference between the mean ± S.D. masses (MT) in the different subgroups (NR0= 115.0 ± 26.6 g; NR15 = 94.8 ± 24.9 g; NR30 = 56.3 ± 28 g; R0 = 76.4 ± 20.1 g; R15 = 72.l ± 17.6 g; R30 = 43.6 ± 17.2 g). Similarly, K and IV decreased. Irrespective of the initial feeding condition, the width of the otolith microincrements started to decrease at the end of the first or second day of restricted feeding. In the subgroups given a restricted food ration for 30 days (NR30 and R30), this decrease reached a plateau at about day 30, which was maintained even when the restriction had ended. This slowed growth did not lead to any marked halt in microincrement formation, since there were no significant differences (ANOVA; P>0.05) in the numbers of increments counted in the various subgroups. The results show that in 153 day old fish, a period of severe food restriction, even if prolonged (15 to 30 days), had no influence on the timing of the laying down of microincrements but only affected their growth.
Effect of temperature and dissolved oxygen concentration on the metabolic rate of the turbot and the relationship between metabolic scope and feeding demand
Authors: Mallekh R. , Lagardère J. P.
Published: April 2005

Turbot Scophthalmus maximus maximum oxygen uptake following feeding and exhaustive exercise increased from 107 mg O2 kg−1 h−1 at 6° C to c. 218 mg O2 kg−1 h−1 at 18° C, then increased slightly from 18 to 22° C to 224 mg O2 kg−1 h−1. Standard oxygen uptake increased exponentially as a function of temperature from 11 mg O2 kg −1 h−1 at 6° C to 66 mg O2 kg−1 h−1 at 22° C. Gradual reduction in oxygen concentration to 87–90% air saturation at 6, 10. 18° C and <80% at 14 and 22° C limited the maximum metabolic rate but, supersaturation (>100% saturation) had little effect. Metabolic scope attained a maximum of 176 mg O2 kg−1 h−1 at 18° C. Interpolation of the results showed that this value changed little between 16 and 20° C. It is suggested that this temperature range is optimal for turbot of c. 500 g. A comparison with a previous study on feeding demand in intensive farming conditions showed a linear relationship between appetite and metabolic scope. It is concluded that the ability of a fish to supply energy (including the energy requirement of digestive metabolism) above a standard level is a limiting factor in the manifestation of its feeding demand.
Inhibitory effect of sodium bicarbonate on the motility of sperm of Japanese eel
Authors: Tanaka S. , Zhang H. , Yamada Y. , Okamura A. , Horie N. , Utoh T. , Mikawa N. , Oka H. P. , Kurokura H.
Published: April 2005

Sperm motility of Japanese eel Anguilla japonica was depressed from 59.1 to 1.1% when NaHCO3 concentration increased from 0 to 150 mM. In 25 mM NaHCO3, when pH of the medium was 6.2, 7.2, 8.2, 9.2 and 10.2, relative sperm motility was 0, 0, 55.8, 93.7 and 136.6%, respectively to that of the control (0 mM NaHCO3). The remarkable effect in acid or neutral condition indicates that free‐CO2 (liberated CO2 and H2CO3) is a key factor for the motility inhibiting effect of NaHCO3.
Composition of main haematopoietic compartments in normal and bled channel catfish
Authors: Fijan N.
Published: April 2005

Differential cell counts showed that the head and trunk kidney of control and bled channel catfish Ictalurus punctatus had myeloid characteristics. They contained lymphoid and granuloid cells, thrombocytes, erythroid and agranular cells in decreasing order of abundance (%). Among the blast and precursor cells, the most numerous erythroid ones were followed by granuloid, lymphoid and agranular ones. The main changes after blood withdrawal were the decrease of thrombocytes and the increase of precursor cells in both kidney parts. In the group examined 7 days after bleeding the head kidney had a higher percentage of erythroid cells and lymphocyte precursors than the trunk kidney while the latter had more granuloid cells and their precursors. Basophils were present (c. 1%) in both regions of the kidney of all groups. The spleen was predominantly a lymphatic organ. It contained c. 80% lymphoid cells, a higher incidence of granulated lymphocytes than in kidneys, 15% thrombocytes and 1.4% agranular cells. Blood withdrawal caused an increase of thrombocytes, a decrease of lymphoid cells and an increase of erythroid precursors in the spleen. The last probably stemmed from the circulation. While haematocrit values failed to indicate the anaemic state in the bled groups, the differential red blood cell count showed dramatic differences between the control and bled groups as well as between the two groups in different stages of recuperation from the blood loss.
Important considerations for methaemoglobin measurement in fish blood: assay choice and storage conditions
Authors: Lacey J. A. , Rodnick K. J.
Published: April 2005

Spectrophotometric assays of methaemoglobin (metHb) in rainbow trout Oncorhynchus mykiss, channel catfish Ictalurus punctatus, tilapias Tilapia niloticus and Tilapia zillii and white sturgeon Acipenser transmontanus, under baseline conditions, were low (<4%) for each species, and yet higher than human values (<1%). MetHb results for a given fish species varied significantly between assays and two assays were deemed unacceptable for particular animals. For rainbow trout, white sturgeon, and the two species of tilapia, the Dubowski method gave uncharacteristically high estimates of metHb. MetHb could not measured in tilapia blood using the Evelyn & Malloy method due to spectral interference. Only the Horecker & Brackett assay worked well for all species. Storage conditions were extremely important in the quantification of metHb in rainbow trout blood. For consistent values, samples can be stored up to 4 h on ice (0° C) or at least 20 days under liquid nitrogen (− 196° C). Auto‐oxidation, however, elevates rainbow trout metHb at − 20 and − 80° C. It should not be assumed that the blood of fishes and humans perform similarly during assays of metHb.
First report on embryos of Isistius brasiliensis
Authors: Gadig O. B. F. , Gomes U. L.
Published: April 2005

Embryos of Isistius brasiliensis, from southern Brazil, are described for the first time. This paper confirms the lecithotrophic mode of embryonic development in this species.
Genetic relationships among five nemipterid fish species from the Indian coast using allozyme analysis
Authors: Menezes M. R. , Arolkar U. , Rathod V.
Published: April 2005

Based on Nei's genetic distance Nemipterus peronii and Nemipterus japonicus showed a greater affinity to Parascolopsis aspinosa than to the other Nemipterus species studied. Significant differences between the Indian west and east coast samples of N. japonicus were detected. Polymorphic (P<0.95) and diagnostic loci suitable for stock delineation and species identification were observed.
Aggression and growth as an effect of size composition in groups of Arctic charr
Authors: Brännäs E. , Linnér J. , Eriksson L.‐O.
Published: April 2005

Aggressive interactions were initially higher in groups comprised of equally sized large and intermediate Arctic charr Sahelinus alpinus than in groups of small sized individuals and in groups with a normal size distribution. Size composition had no effect on growth.
Is selection for territorial aggression in brown trout density‐dependent?
Authors: Bohlin T. , Pettersson J. C. E. , Johnsson J. I.
Published: April 2005

A comparison between a high‐density (migratory) and a low‐density (stream‐resident) population of brown trout Salmo trutta, from the same stream, showed there was no support for the view that aggression was density‐dependent.
The upper critical thermal limits for alevins of Arctic charr from a Norwegian lake north of the Arctic circle
Authors: Elliott J. M. , Klemetsen A.
Published: April 2005

Mean values ±95% CL of the upper incipient (TIL) and ultimate (TUL) lethal temperatures, determined at five acclimation temperatures (TA), increased for TIL from 19.2 ± 0.4° C (TA 0.5° C) to 21.0 ± 0.4° C (TA 20° C), and for TUL from 22.6 ± 0.1° C (TA 0.5° C) to 26.6 ± 0.4° C (TA 20° C). Mean values were close to those obtained for Arctic charr alevins from Windermere (north‐west England). These comparative data for alevins, and previous data for 0+ year parr, indicate negligible geographical variation in the thermal limits of Arctic charr.
The inheritance of heteroplasmy in guppies
Authors: Taylor J. S. , Breden F.
Published: April 2005

Guppies Poecilia reticulata from the Rio Grande, Trinidad are heteroplasmic; individuals possess up to nine different‐sized mtDNA haplotypes. A PCR survey of mtDNA length variation that included mothers and embryos suggests that a large number of mitochondrial genomes (possibly within a much smaller number of organelles) pass from one generation to the next.