bluuebunny/crossref_metadata_2025 huggingface dataset:
Feeding behaviour of Japanese flounder larvae under laboratory conditions
Authors: Dou S. , Seikai T. , Tsukamoto K.
Published: April 2005

Tank–reared Japanese flounder larvae, Paralichthys olivaceus, had a major feeding peak in the morning and a secondary peak in the afternoon throughout the larval development, with light being the primary factor regulating their feeding activity. The larvae consumed rotifers in preference to Artemia for up to 10 days, after which the food preference shifted to Artemia. Feeding rates of the larvae prior to 10 days post–hatch depended on prey density, but in the old larvae, feeding rates were independent of prey density. Maximum feeding rate occurred at 19° C. The occurrence of the attack posture, after its onset at first feeding (2 days post–hatch), increased up to 25 days, began to decrease when the larvae prepared to settle down, then disappeared after settlement. The occurrence frequency of the attack posture was positively related to fish density, but inversely related to starvation duration, and occurred most frequently at 19° C. This posture depended on prey density in larvae prior to 10 days post–hatch, but became independent of prey density as the larvae developed. It was obvious that, for flounder larvae, attack posture was a behavioural character closely related to feeding and subject to larval development and environmental factors.
Operational sex ratio influences the opportunity for sexual selection in guppies
Authors: Jirotkul M.
Published: April 2005

The opportunity for sexual selection was greater when the operational sex ratio (OSR) in guppies Poecilia reticulata was biased towards males. This could be due to an increase in both male‐male competition and female mate choice under male‐biased OSR.
Impoundment impact on fish in the Warta River: species richness and sample size in the rarefaction method
Authors: Głowacki Ł. , Penczak T.
Published: April 2005

Over 11 years of study, fish species richness decreased continually and significantly in the tailwater of the Warta River (Poland). The smallest sample size required for estimating species richness of fish communities in the tailwater increased. As the rarefaction method has rarely been applied in fishery research, its strengths and drawbacks in cases similar to this are discussed.
Oocyte development in summer flounder: seasonal changes and steroid correlates
Authors: Merson R. R. , Casey C. S. , Martinez C. , Soffientino B. , Chandlee M. , Specker J. L.
Published: April 2005

Seven ovarian stages are described in summer flounder Paralichthys dentatus. In the prespawning season plasma oestradiol levels increased in maturing fish with lipidogenic oocytes and gonadosomatic index increased in fish undergoing vitellogenesis. Atretic oocytes present in the postspawning season indicated which individuals may have spawned. The pattern of oocyte development is similar to that of other flatfishes and some teleosts. The summer flounder was unusual in having a long lipid uptake phase (oocyte diameter up to 301 μm) prior to any indication of vitellogenin (yolk protein) uptake. This information will be useful in the construction of an updated maturity schedule for the wild population.
The effect of different initial size distributions on the growth of Atlantic halibut
Authors: Stefánsson M. Ö. , Imsland A. K. , Jenssen M. D. , Jonassen T. M. , Stefansson S. O. , FitzGerald R.
Published: April 2005

Growth rate of individually tagged medium–sized (249±6·9 g) juvenile halibut was 18% lower when medium sized fish were reared alone (treatment Mm) as compared with rearing with either large/dominant (382±12·1 g) (Ml) or small/subordinate (158±3·1 g) (Ms) conspecifics. The coefficient of variation of weight of medium–sized fish increased with weight in both the Mm and the Ml group whereas it was stable in the Ms group. Size rank correlation between initial and final weight was highest in the Mm group and lowest in Ms. A negative rank correlation was found also between initial weight and overall growth rate for the Ms treatment groups but not the other groups. It is hypothesized that interactions between similar–sized individuals in the Mm treatment group had an inhibiting effect on growth as social hierarchies were being resolved.
Effects of size asymmetry on aggression and food acquisition in Arctic charr
Authors: Lahti K. , Lower N.
Published: April 2005

The feeding rate of a group (DS) of two small, two medium and two large 1+ Arctic charr Salvelinus alpinus was higher than in a group of six fish of the same size (SS), suggesting that size distribution had an effect on feeding behaviour, with a correlation between the size of the fish and the amount of food eaten–the largest fish eating the most. Against predictions, rate of aggression was not higher in the SS groups; rather there was a modest tendency of higher aggression among individuals in the DS groups.
Pools as refugia for brown trout during two summer droughts: trout responses to thermal and oxygen stress
Authors: Elliott J. M.
Published: April 2005

In non–drought years (1977, 1985), temperatures and oxygen concentrations from 1 to 14 July at the deepest point in each of five pools in Wilfin Beck were similar with ranges of 12–18° C and 7·8–9·8 mg l–1. TroutSalmo truttawere present in all pools. In drought years (1976, 1983), temperature increased and oxygen concentration decreased as pool size decreased. In the two smallest pools, they were outside the thermal and oxygen limits for trout (ranges for both pools 24–29° C, 1·2–2·5 mg l–1), and trout were absent. Values in a medium–sized pool were close to the incipient lethal levels and a few juvenile trout were present in both drought years. The lowest temperatures and highest oxygen concentrations were recorded in the two largest pools (ranges 20–25° C, 3·6–4·8 mg l–1) and trout of all ages (0+ to adults) were present in both drought years. In these two pools, both temperature and oxygen concentration decreased from the surface to the deepest point in the pool. Trout preferred lower temperatures near the pool bottom rather than higher oxygen concentrations near the surface, but some fish moved towards the surface at night when the pool cooled slightly. These field results were discussed in relation to lethal values recorded for brown trout in the laboratory, and there was general agreement between field and laboratory values. Trout in the drought years occurred at temperatures close to, or below, the incipient lethal value of 24·7° C (+0·5) and also at the highest oxygen concentrations, but only when these were at temperatures below the incipient lethal value.
Biplot presentation of diet composition data: an alternative for fish stomach contents analysis
Authors: De Crespin de Billy V. , Dolegec S. , Chessel D.
Published: April 2005

A multivariate analysis derived from principal components analysis (PCA), and which allows the investigation on diet composition data, is introduced. To illustrate the method, prey composition data of stomach contents of brown troutSalmo truttaL. collected in a regulated stream were used. The diet composition, foraging strategies and related patterns of fish diet variation were analysed at a macrohabitat scale (i.e. riffles and glides) by way of biplots. These graphical presentations were consistent with PCA on proportions.
Age, sex ratio and timing of the catch of kelts and ascending Atlantic salmon in the subarctic River Teno
Authors: Niemelä E. , Makinen T. S. , Moen K. , Hassinen E. , Erkinaro J. , Lansman M. , Julkunen M.
Published: April 2005

By 15 June, 82% of the catch of Atlantic salmon Salmo salar kelts had been taken from the middle part of River Teno, northern Scandinavia. The median date of capture was 4 June for males and 8 June for females. Salmon of 1–4 sea–winters (SW) of both sexes survived spawning to return to sea as kelts. Among males, 1 SW kelts were caught earliest in the spring and 3 SW latest, but among females 4 SW were earliest, then 3 SW and finally 1 and 2 SW. There were 17 river and sea–age combinations among the kelts compared with 23 among the ascending salmon. The smolt age distribution and the mean smolt age differed significantly only between female 2 SW ascending salmon (3·97 years) and kelts (4·14 years). The proportion of 1 SW females was higher and that of 3 SW males lower among kelts than among ascending salmon. The proportion of males among 1 SW ascending salmon was 80% but among kelts only 57%. Similarly, the proportion of males among 3 SW fish was 21% for ascending salmon but only 7% for kelts. Hence overwinter mortality was higher among males. Male and female kelts of 1 and female kelts of 2 SWhad a greater mean length than ascending salmon in corresponding groups indicating a better survival of larger fish within an age group. Grilse ascend rivers after most kelts have left, but the main catch of ascending 2–3 SW salmon takes place concurrently with kelts leaving the river, inadvertently targeting kelts in the fishery.
Plasma non‐esterified fatty acid profiles and 17β‐oestradiol levels of juvenile immature and maturing adult American eels in the St Lawrence River
Authors: Ccottrill R. A. , McKinley R. S. , Van Der Kaak G. , Dutil J‐D. , Reid K. B. , McGrath K. J.
Published: April 2005

American eels Anguilla rostrata, collected from three distinct locations along the St Lawrence River (Lake St Lawrence, Quebec City and Kamouraska), were thought to consist entirely of out‐migrating adults at Quebec City and Kamouraska and of both resident and migrants at Lake St Lawrence. The mean plasma levels of 17β‐oestradiol closely paralleled the trend observed with gonadosomatic index (IG) and oocyte development. The highest levels of 17βoestradiol and IG were observed in Quebec City and Kamouraska, while the levels observed in the resident eels from Lake St Lawrence were very low. Generally, the concentration of total plasma non‐esterified fatty acids (NEFA) appeared to follow the trend of 17β‐oestradiol and IG and increased with sexual maturity. However, the most sexually mature group, eels from Kamouraska, had the lowest total plasma NEFA levels. The reason for the drop is not clear at present. In addition, a number of shifts in the plasma NEFA profiles of American eels did occur during their migration in a downstream direction, with several fatty acids either increasing or decreasing in relative abundance. The ratio of n3: n6 fatty acids declined with increasing sexual maturity as most n3 fatty acids became less abundant. Although the correlation between gonadal development and the relative concentration of individual fatty acids was not always clear, both arachidonic acid (20: 4n6) and docosahexaenoic acid (22: 6n3) were significantly higher in the plasma of out‐migrating adults than in resident yellow phase eels.
Seasonal variations in the energy density of fishes in the North Sea
Authors: Pedersen J. , Hislop J. R. G.
Published: April 2005

The energy density (ED, kJ g‐1 wet mass) of saithe Pollachius virens, haddock Melanogrammus aeglefinus, whiting Merlangius merlangus, Norway pout Trisopterus esmarki, herring Clupea harengus, sprat Sprattus sprattus, sandeel Ammodytes marinus and pearlsides Maurolicus Muelleri, from the North Sea, increased with total length, LT. However, there was not always a significant (P>0·05) linear relationship between LT and ED. Seasonal differences in ED were obvious in mature fish, while geographical differences were insignificant. For all species there was a highly significant correlation (P<0·0001) between the percent dry mass of the fish (DS) and ED. A general relationship was established for gadoids and sandeel ED=–3·1492+0·3459 DS and herring ED=–4·6395+0·4170 DS. Thus seasonal and size‐specific data on ED needed for bioenergetics and gastric evacuation models can be determined simply from DS, which is considerably less costly and time consuming than calorimetry or proximate analysis.
The biology of Roule's goby in the Kvarner area, northern Adriatic Sea
Authors: KovačIć M.
Published: April 2005

Roule's goby Gobius roulei in the Kvarner area of the northern Adriatic Sea attained ≥ 87.5 mm LT and an age of 7 years. In both sexes gonad development began in their second year. All males were mature by 3 years, and females by 4 years. Fecundity was related to LT and varied between 1200 and 8000 eggs. The breeding season lasted from April to August. Nests were built under empty shells of Pitaria chione or stones. Roule's goby was a predator and picker, feeding mostly on mobile benthic fauna, including bivalves, gastropods, polychaets, pagurids, mysids, gammarids and fishes. Larger specimens ate mainly macrofauna, while smaller specimens ate both meiofauna and macrofauna.
Movement and stock structure of narrow‐barred Spanish mackerel as indicated by parasites
Authors: Lester R. J. G. , Thompson C. , Moss H. , Barker S. C.
Published: April 2005

Data from permanent parasites (juvenile trypanorhynchs and anisakids) indicated that Spanish mackerel Scomberomorus commerson from four sites on the west coast of Australia, Abrolhos. Shark Bay, Exmouth and Onslow, intermingled and were probably all drawn from the same stock. Fish from Broome, Kupang (Indonesia), Groote Eylandt‐Torres Strait and the east coast of Australia had distinct faunas of permanent parasites and probably each belonged to a different stock. There was evidence of movement of fish between Broome and the west coast. Abundances of temporary parasites (gill copepods and monogeneans) suggested that males and females on the west coast migrated separately because in several cases the parasite fauna of one sex was more similar to that offish in an adjacent area than to the opposite sex in the same area.
Behaviour, growth and survival of redfish larvae in relation to prey availability
Authors: Laurel B.J. , Brown J. A. , Anderson R.
Published: April 2005

Growth, survival and condition of redfish larvae Sebastes spp., reared in the laboratory (0, 500 1500 and 4500 prey l‐1) were highest in the 1500 prey l‐1 treatment. Significantly lower larval growth and survival in the 4500 prey l‐1 treatment corresponded with lower prey bite: orient ratios in later weeks, suggesting that larvae were unable to forage efficiently at high prey densities. While these prey densities are higher than those reported in the field, naturally co‐occurring Atlantic cod Gadus morhua larvae require higher prey densities when reared under similar conditions in the laboratory. These data suggest that prey availability may not be as limiting to redfish as for other commercially important marine species.
Developmental change in RNA: DNA ratios of fed and starved laboratory‐reared Japanese flounder larvae and juveniles, and its application to assessment of nutritional condition for wild fish
Authors: Gwak W. S. , Tanaka M.
Published: April 2005

Starved Japanese flounder Paralichthys olivaceus larvae were characterized by relatively lower levels of RNA content throughout their early life stages. Significant differences in the RNA: DNA ratios were found between fed and starved fish, and appeared to increase as starvation proceeded. Ontogenetic changes in RNA: DNA ratios were clearly observed during metamorphosis, especially decreasing during the period from the late‐metamorphic to postmetamorphic stages. The criteria established from these laboratory experiments, were applied to the nutritional condition of wild larvae and juveniles collected in Wakasa Bay, Sea of Japan in 1994 and 1995 by measuring RNA and DNA content. Starved fish were mainly found in stage I (settling stage) fish during the late season of settlement in 1995. This suggests that starvation could be associated with settlement in Japanese flounder.
Homing behaviour of stream‐dwelling brook charr following experimental displacement
Authors: Bélangerz G. , Rodríguez M. A.
Published: April 2005

Precise homing of 24 brook charr Salvelinus fontinalis (157–215 mm LF), displaced from their site of capture in a natural stream, was rare both in fish displaced upstream and those displaced downstream. Most fish settled in preferred habitats (pool or glide) away from their home site and showed restricted movement up to the pre‐spawning period. Partial return responses, however, were stronger in fish displaced downstream than in fish displaced upstream. Most fish displaced downstream showed directional upstream movement soon after displacement, whereas fish displaced upstream did not show directional upstream movement, suggesting that it is primarily olfactory cues from upstream locations, and not positive rheotaxis, which mediate the return response. Homing success was unrelated to distance of displacement, body size, or population density in the home site, but daily mobility increased with body size for fish displaced downstream. There was no evidence of switching between specific areas between night and day, nor of differences between daytime and night‐time mobility, suggesting that diel movement cycles did not bias the evaluation of homing success. Site attachment in stream‐dwelling brook charr may be characterized as persistent (undisturbed fish remain stationary over long periods), but readily disrupted by involuntary displacement.
Migration of bream between the main channel and floodplain lakes along the lower River Rhine during the connection phase
Authors: Grift R. E. , Buljse A. D. , Breteler J. G. P. Klein , Densen W. L. T. van , Machiels M. A. M. , Backx J. J. M.
Published: April 2005

Mature bream (>30 cm LF) dominated the fish communities in floodplain lakes along the lower River Rhine in The Netherlands, in terms of biomass, in all lakes at all times. In some lakes bream made up 99% of the total fish biomass. While immature, medium–sized bream (10‐30 cm) and white bream and roach were abundant in the main channel of the river, these species were almost absent from the floodplain lakes. Inundation of the floodplains did not lead to spatial homogenization of species and length distributions. Small bream (<10 cm) left the floodplains to become resident in the main channel until maturity. Once mature (c. 30 cm), they returned to the lakes during the next inundation and stayed there. Mature bream that moved into the lakes were significantly smaller and had a lower condition than the resident bream. Turbid clay‐pits were probably important sources of bream for the lower Rhine and the recruitment of the 0+ year group of bream to the riverine population was influenced by their discharge pattern.
Back‐calculation of fork length of white‐spotted charr from scales: a comparison between major and minor axes measurements
Authors: Morita K.
Published: April 2005

The back‐calculated lengths of white‐spotted charr Salvelinus leucomaenis from scales obtained using two alternative measurement axes (major axis v. minor axis) were compared. The minor axis provided a more accurate estimate of past length than the major axis.
Diet breadth variability in larval blue whiting as a response to plankton size structure
Authors: González‐Quiróas R. , Anadóan R.
Published: April 2005

Diet breadth (measured as the S.D. of the log of prey size per larvae; SLH) of blue whiting micromesistius poutassou larvae followed a quadratic equation with larval size. In small larvae, diet breadth in terms of size (SLH), the mean and the maximum of the log of prey size per larvae (MLH and XLH, respectively) increased with larval size as prey size selection shifted to larger prey. In contrast, large larvae tended to reduce diet breadth of prey sizes ingested, focusing on the larger prey that were abundant, instead of raising the upper limit of prey sizes because of the low abundance of larger prey. Except for larvae at the onset of first feeding, number of prey stayed constant or decreased in relation to larval size. Both patterns (in small and large larvae) maintained a constant rate of increase of gut carbon content with increase in larval size. Large larvae appear to maintain the increase in gut carbon content during ontogenetic development by reducing diet breadth (SLH) and increasing selection towards the larger prey that are abundant.
Oreoglanis infulatus, a new species of glyptosternine catfish (Siluriformes: Sisoridae) from central Vietnam
Authors: Ng H. H. , Freyhof J.
Published: April 2005

A new species of glyptosternine catfish, Oreoglanis infulatus, is described from the Lam River drainage in central Vietnam. The new species is distinguished from all its congeners by possessing the following combination of characters: a dark band running across the anal fin, a lunate and uniformly dark caudal fin, the lower lip lacking a medial notch and with a lobulate posterior margin, maxillary barbel with a rounded tip, length of caudal peduncle 19·0–22·6 %LS, depth of caudal peduncle 2·6–3·2 %LS, post‐adipose distance 6·8–8·0 %LS, eye diameter 10·5–12·1 %LH, 12 principal caudal‐fin rays.
A gastric evacuation model for three predatory gadoids and implications of using pooled field data of stomach contents to estimate food rations
Authors: Andersen N. G.
Published: April 2005

The general applicability of the square root model to describe gastric evacuation in predatory gadoids independently of meal size was verified through experiments on whiting Merlangius merlangus, saithe Pollachius virens and cod Gadus morhua fed different fish and crustacean prey. Gastric evacuation rate was related by a negative power function to energy density of fish prey over an extended range from 3·4 to 11·5 kJ g‐1 of the effector variable. Gastric evacuation of crustacean prey seemed to depend on the characteristics of their exoskeleton. Gastric evacuation of mixed meals composed of fish prey with different energy densities could be described as a function of the overall energy density. The evacuation rate of each of the prey could be described directly by their share of the stomach content. A full gastric evacuation model including predator size, temperature and prey energy density was established for whiting, saithe and cod. It was demonstrated that estimates of food rations might be severely biased by use of mean values for prey composition and total mass of stomach contents.
Dynamics of the shallow‐water fish assemblage of the Patos Lagoon estuary (Brazil) during cold and warm ENSO episodes
Authors: Garcia A. M. , Vieira J. P. , Winemiller K. O.
Published: April 2005

In southern Brazil, cold (La Niña) and warm (El Niño) episodes of the El Niño Southern Oscillation (ENSO) phenomenon cause drought and high rainfall, respectively. The low precipitation and freshwater outflow associated with La Niña during 1995–1996 were associated with an increase in the abundance of marine species in the Patos Lagoon estuary. During the 1997–1998 El Niño, high precipitation and river discharge were associated with low abundance of marine species in the estuary. ANOVA results showed a higher abundance during La Niña than El Niño for estuarine resident (RES) and estuarine dependent (DEP) fishes. During La Niña catch per unit of effort (CPUE) of RES increased from the marine to estuarine area, but during El Niño CPUE increased at the marine area and diminished during summer and autumn in some estuarine sites. DEP fishes had an opposite abundance pattern. During La Niña, these fishes were abundant at the coastal marine area and along some estuarine sites, but during El Niño, CPUE remained almost the same at the marine area but dropped along some estuarine sites. These different abundance patterns for dominant fish groups yielded a positive interaction between stations and climatic events. With higher river discharge and the consequent decline of dominant euryhaline fishes, such as Mugil platanus and Atherinella brasiliensis, freshwater species increased in abundance and richness in the shallow waters of the stuary. The ENSO phenomenon influences precipitation and estuarine salinity in southern Brazil and thereby seems to have a strong influence on recruitment, immigration, and emigration dynamics of fish species living within and adjacent to estuarine habitats.
Changes in ion content and transport during development of embryonic rainbow trout
Authors: Barrett K. J. , McDonald D. G. , O.'Donnell M. J.
Published: April 2005

Wet mass and water content of four lots of whole eggs did not change throughout embryonic development of rainbow trout Oncorhynchus mykiss. Eggs in all four lots accumulated Na+. Eggs in lots 2 and 4 also accumulated Ca2+ and Cl‐, whereas eggs in lot 1 showed no significant change in Ca2+ or Cl‐ and eggs in lot 3 showed no change in Cl‐and a small loss of Ca2+. Although the Na+ content of embryonic tissues increases in the later stages of development, the yolk sac content remained constant, indicating uptake of Na+ from the environment. Na+ uptake by whole eggs was non‐saturable, consistent with diffusion of Na+ across the chorion into the perivitelline fluid. Na+ uptake in dechorionated embryos was saturable, as was Ca2+ uptake by both whole eggs and dechorionated embryos, consistent with active uptake or facilitated diffusion mechanisms at the surface of embryos. Very low Ca2+ uptake rates in dechorionated embryos suggest that the Ca2+ uptake mechanism is not fully developed until after hatching.
The influence of fish size size on the avoidance of hypoxia and oxygen selection by largemouth bass
Authors: Burleson M. L. , Wilhelm D.R. , Smatresk N. J.
Published: April 2005

When an oxygen gradient ranging from c. 10 to 95% air saturation was formed in a 5 m chamber, largemouth bass Micropterus salmoides avoided water in which dissolved oxygen values were <27% air saturation. There was a significant (P<0·05) correlation between fish mass and the level of dissolved aquatic oxygen that was selected. Small fish (23–500 g) utilized waters of lower oxygen levels than did the larger fish (1000–3000 g). The results of this study suggest that largemouth bass are able to sense and avoid hypoxic water, and select aquatic oxygen tensions that maintain their metabolic scope for growth and activity.
Development of the bony skull in common sole: brief survey of morpho‐functional aspects of ossification sequence
Authors: Wagemans F. , Vandewalle P.
Published: April 2005

The postembryonic development of the bony cephalic skeleton in the common sole Solea solea, observed from hatching to the juvenile stage or postmetamorphic larva, appears to follow a similar chronological order to that observed in other Pleuronectiformes and Perciformes and the sequence in bone formation is a response to functional demands. At hatching, S. solea has no bony structure. On day 4, only the outlines of maxillaries and opercular bones are visible. On day 6, a thin parasphenoid appears between the orbits and isolates the braincase from the buccal cavity making food ingestion possible without any impact on the brain. On day 8, the dentaries form and two small preopercular bones appear on each side of the head. On day 9, at weaning from the yolk sac, branchial arches support the gill filaments (used for respiration and trapping phytoplankton which pass through the open mouth). On day 10, the premaxillaries develop in front of the maxillaries. The superimposing of the maxillaries and the premaxillaries is a typical feature of species possessing an acanthopterygian protractile mouth at the adult stage. On day 12, the frontals develop above the orbits and the set of opercular bones is complete. On day 18, the migration of the left eye begins. On day 20, the left eye has moved to the median crest of the head. On day 23, both eyes are located on the same side. On day 26, the braincase is formed by a basioccipital, exoccipitals, pterotics, sphenotics and a supraoccipital. On day 50, new structures have appeared, others have developed and have undergone an extensive remodeling due to metamorphosis.
Microhabitat use by longfin eels in New Zealand streams with contrasting riparian vegetation
Authors: Broad T. L. , Townsend C. R. , Closs G. P. , Jellyman D. J.
Published: April 2005

Longfin eels Anguilla dieffenbachii caught by electrofishing, in Lee Stream, a tributary of the Taieri River, New Zealand, were significantly longer in pools than in riffles, particularly in summer. Longfin eels were generally shorter in sites with willow. More longfin eels were caught at pasture sites than tussock sites with fewest at sites with willow. Sites judged difficult to access by commercial fishermen had longfin eels that were significantly longer than those in easy‐access sites. More than 80% of longfin eels were captured within 270 mm of banks. The first three components of a principal component analysis explained 40·3% of the variability in microhabitat character recorded at both the capture location and within 0·5 m of capture, and from random locations in each riparian category. Variables strongly associated with longfin eel capture locations were maximum depth (longfin eels used microhabitat of intermediate depth), distance to pool (intermediate), sediment size (finer), sediment depth (deeper), stream idth (intermediate) and flow velocity (slower). Overall there was a greater icrohabitat range in tussock sites but diurnal microhabitat use was most similar to what was available in pasture streams. Winter longfin eel locations were characterized by deeper and finer sediments in contrast to summer and spring locations.
The regurgitation of stomach contents in trawl caught whiting, evidence of a predator size effect
Authors: Staniland I. J. , Hart P. J. B. , Bromley P. J.
Published: April 2005

The rate of regurgitation of food from the stomachs of trawl caught whiting Merlangius merlangus was negatively correlated with fish size. Increased musculature of the oesophageal sphincter in larger fish may enable them to resist the forced expulsion of their stomach contents to a greater extent.
Species‐specific releaser effect of urine from ovulated female masu salmon and rainbow trout
Authors: Yambe H. , Yamazaki F.
Published: April 2005

MT (17α‐methyltestosterone)‐treated immature masu salmon Oncorhychus masou and rainbow trout Oncorhynchus mykiss, exposed to the urine of ovulated females in their non‐reproductive season, made significantly more entries into the channel, of a Y‐maze preference trough, conditioned by the urine of conspecific females than by heterospecifics. Immature, non‐treated controls in both species showed no preference for the urine of ovulated females. These results suggest that, for both species, the releaser pheromones that attract males in the urine are species‐specific. Therefore, utilization of species‐specific chemical signals may be one of the mechanisms of the reproductive isolation in Oncorhynchus species.
Competitive ability and social behaviour of juvenile steelhead reared in enriched and conventional hatchery tanks and a stream environment
Authors: Berejikian B. A. , Tezak E. P. , Riley S. C. , LaRae A. L.
Published: April 2005

SteelheadOncorhynchus mykissfry reared in an enriched hatchery environment (overhead cover, submerged structures and underwater feeders) and a natural stream both achieved significantly greater social dominance ranks than fry reared in a conventional hatchery environment. Dominant fry from enriched tanks and natural stream exhibited greater frequencies of threat displays than dominant fry reared in conventional tanks. Fry reared in the natural stream exhibited greater territory overlap than fry from either hatchery environment. Overall, the results suggest that enriched hatchery environments may act to ameliorate some but not all changes in social behaviour that result from hatchery rearing.
Sexual size dimorphism and male contest in wild Siamese fighting fish
Authors: Jaroensutasinee M. , Jaroensutasinee K.
Published: April 2005

Larger males of the wild Siamese fighting fish Betta splendens were more successful in male contests. There were no differences in fighting duration among treatments. Comparing agonistic behaviour between large and small males in ±1 and ±2 S.D treatments, larger males attacked, chased and performed total agonistic behaviour more than smaller males. There were no differences between larger and smaller males concerning other agonistic behaviour during fighting. Females presented with two potential mates of different sizes did not prefer larger males.
Mitochondrial phylogeny and biogeographic affinities of sea breams of the genus Diplodus (Sparidae)
Authors: Summerer M. , Hanel R. , Sturmbauer C.
Published: April 2005

Phylogenetic analyses, using 482 bp of the mitochondrial 16S rDNA and 461 bp of the control region of 16 Diplodus species and Oblada melanura, Pagellus bogaraveo and Pagellus acarne, all close relatives of Diplodus, identified the two representatives of Pagellus as the sister group of Diplodus. Oblada melanura was confirmed as the sister taxon of D. puntazzo, despite its different dental morphology and ecology. Within the genus Diplodus, three clades were identified, the first containing D. annularis and D. bellottii, the second D. vulgaris and D. prayensis, and the third comprising three subclades. These were formed by O. melanura clustering with D. puntazzo, D. fasciatus with D. cervinus, and by the Diplodus sargus sub‐species assemblage which also included the West Atlantic taxa D. argenteus, D. bermudensis, D. holbrooki, and the Red Sea endemic D. noct. All members of the D. sargus assemblage were genetically closely related. Among them, D. sargus lineatus from the Cape Verde islands was resolved as most ancestral branch, pointing to the possibility that the diversification and spread of the D. sargus assemblage originated in this region. The hypothesis of stepwise speciation following colonization events within the D. sargus complex is fully supported by phylogenetic reconstruction.
Investigating a major assumption of predictive instream habitat models: is water velocity preference of juvenile Atlantic salmon independent of discharge?
Authors: Holm C. F. , Armstrong J. D. , Gilvear D. J.
Published: April 2005

The mean column velocity preference of juvenile Atlantic salmon Salmo salar (LF 30–55 mm) was investigated by observing their spatial pattern of habitat use in a laboratory flume while varying discharge (Q) over a 18‐fold range (Q=2·6–46·8l s‐1). Based on 341 fish observations at three discharges (Q=2·6, 15·0 and 46·8l s‐1), three separate velocity preference curves were developed using standard procedures. The mean column velocities measured at 0·6 depth for the fish positions at the set low, medium and high discharges had medians of 7, 10 and 24 cm s‐1, respectively, and varied significantly between the discharges. Across the range of flows, the fish utilized mean column velocities between 0 and 56 cm s‐1, but the three velocity preference curves differed. Differences between juvenile Atlantic salmon use of habitat, defined according to mean column velocities at different discharges, were greatest at the lower end of the available range of velocities (<20 cm s‐1). Weighted usable area (WUA), the output of the instream flow model PHABSIM that is used to describe the available habitat at a given discharge, was calculated for the flume using the preference curves built at the three set discharges. The model was highly sensitive to differences between the three preference curves and WUA varied by up to a two‐fold difference. Furthermore, habitat‐discharge relationships derived from the three preference curves were very different. Predicted habitat losses across the modelled range of discharges varied by up to 150% depending upon which velocity preference curve was used in the model. Thus, the assumption that a single preference curve can be applied across a range of discharges is not valid and is likely to result in large errors when employing PHABSIM and other models that use similar principles.
Reproductive apparatus and mating system in two tropical goby species
Authors: Mazzoldi C.
Published: April 2005

Field observations demonstrated that two gobiid species Amblygobius nocturnus and Valenciennea muralis have a monogamous mating system. Histological analyses showed an extreme reduction of male accessory organs relative to other gobiids in A. nocturnus, and their complete absence in V. muralis.
Stress induced by hooking, net towing, elevated sea water temperature and air in sablefish: lack of concordance between mortality and physiological measures of stress
Authors: Davis M. W. , Olla B. L. , Schreck C. B.
Published: April 2005

In a series of laboratory studies designed to simulate bycatch processes, sablefish Anoplopoma fimbria were either hooked for up to 24 h or towed in a net for 4 h and then subjected to an abrupt transfer to elevated sea water temperature and air. Mortality did not result from hooking or net towing followed by exposure to air, but increased for both capture methods as fish were exposed to elevated temperatures, reflecting the magnifying effect of elevated temperature on mortality. Hooking and exposure to air resulted in increased plasma cortisol and lactate concentrations, while the combination of hooking and exposure to elevated temperature and air resulted in increased lactate and potassium oncentrations. In fish that were towed in a net and exposed to air, cortisol, lactate, potassium and sodium concentrations increased, but when subjected to elevated temperature and air, no further increases occurred above the concentrations induced by net towing and air, suggesting a possible maximum of the physiological stress response. The results suggest that caution should be exercised when using physiological measures to quantify stress induced by capture and exposure to elevated temperature and air, that ultimately result in mortality, since the connections between physiological stress and mortality in bycatch processes remain to be fully understood.
Diet of post‐smolt and one‐sea‐winter Atlantic salmon in the Bothnian Sea, Northern Baltic
Authors: Salminen M. , Erkamo E. , Salmi J.
Published: April 2005

Until July, post‐smolt salmon Salmo salar (n=337; 129–375 mm LT, mean 225 mm) in the Bothnian Sea relied largely on surface fauna (mainly terrestrial insects). From August onwards, fish was the principal food type. The smallest piscivorous post‐smolts were <200 mm, but the main shift to piscivory occurred at sizes of 240–320 mm. Piscivory was promoted by a large smolt size. Almost all one‐sea‐winter (1‐SW) salmon (n=316; 278–524 mm, mean 397 mm) were piscivorous. Over 70% of the post‐smolt and 96% of the 1‐SW salmon with identifiable fish species in their stomachs had preyed on herring Clupea harengus. Other fish prey included the ten‐spined Pungitius pungitius and three‐spined sticklebacks Gasterosteusaculeatus but no sprats Sprattus sprattus. The results support earlier observations of a close relationship between recruitment of herring and production of salmon in the Bothnian Sea, and of the crucial role of smolt size in determining the ability of feeding salmon for utilizing the food resources of the area.
Stock‐specific changes in growth rates, food conversion efficiencies, and energy allocation in response to temperature change in juvenile Atlantic cod
Authors: Purchase C. F. , Brown J. A.
Published: April 2005

Under common environments, populations of laboratory reared (Grand Banks, GB and Gulf of Maine, GOM) and wild caught (Fortune Bay, FB and Bonavista Bay, BB; Newfoundland) juvenile cod Gadus morhua responded similarly to temperature change in specific growth rates, food conversion efficiencies, condition factors, liver water content, and muscle water content. However, GOM cod had higher condition factors, and showed differences from GB cod in phenotypic plasticity of hepatosomatic index to temperature. These differences were not present in a different population comparison between FB and BB cod. All populations had higher growth rates and food conversion efficiencies at warmer temperatures, and exhibited compensatory growth when temperature was increased. The results suggest relatively larger genetic differences between GB and GOM cod than between FB and BB cod, and indicate that the faster growth of southern populations in the wild is not due to a higher genetic capacity for growth rate.
A histological description of intersexuality in the roach
Authors: Nolan M. , Jobling S. , Brighty G. , Sumpter J. P. , Tyler C. R.
Published: April 2005

This paper is an illustrative guide to intersex in the roach Rutilus rutilus, based on 150 intersex individuals. Most intersex roach had female germ cells, or oocytes, within a predominantly male gonad (testis), and/or malformed/intersex reproductive ducts. The number, pattern and developmental stage of oocytes within testicular tissue in intersex fish varied greatly. In most intersex fish, a few primary oocytes, or numerous primary and secondary oocytes, were scattered randomly throughout the testicular tissue (multifocal intersex). In other, more severely feminized individuals, large areas of ovarian tissue were separated clearly from testicular tissue (focal intersex). Almost all intersex individuals had a female‐like reproductive duct (ovarian cavity). In mild cases of intersex (in which the majority of the germ cells were male) the ovarian cavity was present together with the male sperm duct/vas deferens, whilst in certain severe cases, the sperm duct was absent or vestigial.
Environmental factors affecting the spawning burrow selection by the gobiid Valenciennea longipinnis
Authors: Takegaki T.
Published: April 2005

Spawning burrow selection by the longfinned goby Valenciennea longipinnis was studied in the near‐shore moat on coral reefs, Okinawa, Japan. The gobies make several burrows within their home range, and spawn in one of them. To examine the factors important for spawning burrow selection three characteristics were investigated: current strength, burrow length and effect of underground water on the burrow. Among the burrows, pairs tended to spawn in a larger burrow irrespective of their body sizes. Most of the other non‐spawning burrows were too small for a pair to stay together, because hard substrata may prevent the fish from excavating and shaping the burrow as they like. Moreover, pairs preferred to spawn in burrows where the underground water was oozing out, probably because the male's parental burden will decrease due to the higher dissolved oxygen concentration in such burrows. Although current strength may affect a water‐exchange in a V. longipinnis burrow in relation to water‐exchange function of a mound, it did not affect the spawning burrow selection because of the smaller velocity difference among the burrows relative to the daily fluctuation of tidal current.
Respiration rates, ATP content and ionic regulation in hepatocytes of starving lamprey during the pre‐spawning period of their life cycle
Authors: Gamper N. L. , Savina M. V. , Brailovskaya I. V. , Vereninov† A. A.
Published: April 2005

During the winter pre‐spawning migration, lampreys Lampetra fluviatilis stop feeding, and their liver metabolism is reduced substantially. Aerobic ATP production in hepatocytes decreased to one third and ATP content decreased by 50% as compared with the values in autumn. In spite of the decrease of endogenous and phosphorylating (oligomycin‐sensitive) respiration in winter, the oxygen consumption used to drive sodium and potassium pumping through Na,K‐ATPase activity (ouabain‐sensitive respiration) remained virtually constant. Consequently its share in phosphorylating respiration increased from 16·3% in November to 54·2% in February. Potassium influx was similar within the range of ATP content between 2·5 and 1 nmol 10−6 cells and decreases only in hepatocytes which contained <0·8 nmol ATP 10−6 cells.
Relationship between freshwater angling catch of Atlantic salmon and stock size in the River Bush, Northern Ireland
Authors: Crozier W. W. , Kennedy G. J. A.
Published: April 2005

Over 25 years rod catches of Atlantic salmon Salmo salar increased proportionately as stock size increased (r2=0·581, P<0·001), with no overall trend between exploitation rate and stock size (r2=0·016, P>0·5). On a 15 year sub‐set of these data annual effort (P=0·804) and flow (P=0·339) had little significance relative to stock size (P<0·01) on variation in rod catches. Stock size, time, effort and flows had no influence on inter‐annual variation of rod exploitation rate (r2=0·094, P=0·880). Pairwise correlation between variables confirmed these results. In 1998, weekly effort contributed significantly to overall catch variation (P<0·001), while weekly flow did not (P=0·438). These results are discussed in relation to the utility of rod catch data for deriving estimates of stock for spawning target compliance purposes.
The effects of meal size, body size and temperature on gastric evacuation in pikeperch
Authors: Koed A.
Published: April 2005

Prey size had no effect on the gastric evacuation rate of pikeperch Stizostedion lucioperca. The gastric evacuation was adequately described applying an exponent of 0·5 in the power model. Applying length instead of weight of pikeperch in the gastric evacuation model resulted in a change of estimated parameters, in accordance with the weight–length relationship of pikeperch.
Second record of the toadfish Chaunax suttkusi Caruso, 1989 in the Mediterranean Sea
Authors: Ragonese S. , Giusto G. B. , Caruso J. H.
Published: April 2005

A 146 mm, 48 g toadfish Chaunax suttkusi Caruso, 1989 was caught in January 2000 by a commercial bottom trawler o. the Northern Tunisian coast. This is the second record of C. suttkusi in the Mediterranean, caught about 50 km west of the first, 3 years later.
Rainbow trout display a developmental shift in red muscle kinetics, swimming kinematics and myosin heavy chain isoform
Authors: Coughlin D. J. , Burdick J. , Stauffer K. A. , Weaver F. E.
Published: April 2005

Both activation and relaxation times of rainbow trout Oncorhynchus mykiss red muscle were shorter in parr than in older juveniles. Furthermore, parr red muscle had a faster maximum shortening velocity than that of older fish, as estimated with the force‐clamp technique. Parr swam with higher tailbeat frequencies and lower tailbeat amplitude than did older fish across a range of length‐specific steady swimming speeds. The developmental shift in contraction kinetics of red muscle and steady swimming kinematics was associated with a reduction from two or three myosin heavy chain isoforms in parr to one in older juveniles. This transition provides a mechanism to explain the variations in muscle contraction kinetics and swimming performance.
Bile salt‐dependent lipase in larval turbot, as influenced by density and lipid content of fed prey
Authors: Hoehne‐Reitan K. , Kjørsvik E. , Reitan K. I.
Published: April 2005

Turbot larvae were fed three different densities of rotifers (1000, 3000 and 7500 rotifers 1−1) with a low lipid level (< 15% of dry weight) or 7500 rotifers 1−1 with a high lipid level (∼30% of dry weight). The larval consumption of rotifers increased with increasing prey densities and the content of bile salt‐dependent lipase (BSDL) in larvae was correlated positively with the ingestion rate from days 6 to 8. This suggests that BSDL synthesis was stimulated by the amount of ingested prey in the early larval phase. However, growth was highest in larvae receiving the medium prey densities, which indicates that the larvae were not able to digest properly the ingested prey at the higher density. No significant effect on the BSDL content was seen in turbot larvae fed rotifers with a high or low lipid content.
The costs of reproduction to males and females of a paternal mouthbrooding cardinalfish Apogon notatus
Authors: Okuda N.
Published: April 2005

In the cardinalfish Apogon notatus, starving males mouthbrood the eggs, and females are more active than males in courtship and in attacks against conspecific intruders upon their breeding territory, but sexual ornaments are developed in males. Condition factor, hepatosomatic index and fat body‐somatic index declined in both sexes during the breeding season. The deterioration of somatic condition was more severe in females, suggesting that the overall energetic costs were larger for females which produced more than twice as many clutches as males brooded in a season. Selective mortality of females could be due primarily to the depletion of their energy reserves. The increased mortality in females is a possible mechanism for the male‐biased operational sex ratio which may provide the potential for sexual selection on males.