bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of seawater‐acclimatization and release sites on survival of hatchery–reared brown troutSalmo trutta
Authors: Jonsson N. , Jonsson B. , Hansen L. P. , Aass P.
Published: April 2005

To test whether seawater–acclimatization of hatchery–reared anadromous and freshwater resident brown trout before release increased the survival of adults, smolts were retained 0, 2, 4 and 8 weeks in sea water before release. Total recapture rate increased for smolts retained 4 and 8 weeks in sea water before release relative to the controls. This trend was more pronounced for Freshwater resident than for anadromous stocks, Offspring of anadromous fish stayed longer at sea than offspring of freshwater resident fish. Recapture rates in fresh water were higher for brown trout released in the river than in the fjord in the R, Drammen area, but not in the R. Imsa. In both cases, most fish were recaptured in the sea. Moving into the R. Imsa (relative to other rivers) appeared higher for fish released at the mouth of the river (93%) than in the fjord (47%). Judged from the recapture rates, sea survival appeared to be the same whether released in the fjord or at the mouth of the river.
Relationship of plasma steroids to germ cell development and the presence of protamine mRNA in rainbow trout during the induction of spermatogenesis with partially purified salmon gonadotropin
Authors: Budworth P. R. , Senger P. L. , Griswold M. D. , Donaldson E. M.
Published: April 2005

The gonadosomatic index (GSI) of pre–pubertal male rainbow trout, which had been injected biweekly with partially purified salmon gonadotropin (sG–G100, 50 μ mUg kg−1 body weight), increased from 0.05 to 1.85 over 21 weeks from injection, while control GSI remained below 0.05. Plasma testosterone (T) increased from 2 to 11.34 ng ml−1 by week 21 in injected fish, while control level remained below 1.5 ng ml−1. In injected fish plasma 11–ketotestosterone (KT) and 17,20–dihydroxyprogesterone (17α20βP) levels increased from 20.2 to 41.9 and 8.9 to 219.7 ng ml−1 respectively. Plasma T, 11–KT, and 17α20βP were all correlated with the GSI (P<0–001) in injected fish. The most advanced stage of germ cells present in the control fish were spermatogonia. However, in injected fish spermatozoa were present by week 21. Eggs fertilized at this time with spermatozoa from injected fish achieved a 78% fertilization rate, whereas the testicular homogenate was incapable of fertilizing eggs.
Timescale of ovarian maturation in Notothenia coriiceps; evidence for a prolonged adolescent phase
Authors: Everson Inigo
Published: April 2005

Ovarian maturation in Notothenia coriiceps is known to include a period during which yolk deposition begins to take place. This ‘adolescent’ phase was thought originally to last for about 1 year. The results from a 2–year study at Signy Island indicate that this adolescent phase lasts for about 4 years. There is also some evidence to indicate that not all sexually mature fish spawn each season. Two reproductive strategies are considered, one where adverse conditions are accompanied by a failure to spawn and an alternative where fecundity is controlled by the number of small oocytes which ripen.
Energy and ration requirements of juvenile Pacific halibut (Hippoglossus stenolepis) based on energy consumption and growth rates
Authors: Paul A. J. , Paul J. M. , Smith R. L.
Published: April 2005

Growth of captive juvenile Pacific halibut was linearly related to energy consumption (J g−1 day−1) at 4°C by the following equation: growth (% body weight (b.w.) day−1)=0–007 (consumption J g−1 day−1)– 0.192; r2=0.81. Weight gain was independent of size for fish between 9 and 7000 g when growth was expressed as a function of consumption in J g−1 day−1. Maintenance ration determined in feeding–growth experiments averaged 27.4 J g−1 day−1 at 4–0°C. Small halibut ate significantly more food than large fish. Single meals following 2 day fasts averaged 4.1% b.w. for halibut under 100 g, 1.72% b.w. for 1.2 kg fish and 1.1% B.W. for 6.8 kg fish. Both large and small size categories of halibut tended to evacuate their meal in about 3 days even though small fish ate relatively larger meals. Minimum estimates for daily ration to achieve growth rates observed in the Gulf of Alaska were approximately 0.5 to 2.4% b.w. day−1 depending on fish size and whether northern shrimp or yellowfin sole were their prey.
An ultrastructural and immunocytochemical study on the lymphomyeloid tissue in the embryonic kidney of the dogfish, Scyliorhinus canicula
Authors: Lloyd‐Evans P.
Published: April 2005

The central role of the kidney during early development in the dogfish, Scyliorhinus canicula, is haemopoietic. The kidney is the first tissue to become lymphomyeloid and lymphocytes and developing granulocytes are found in the interstitial tissue surrounding the renal tubules. The lymphomyeloid role of the kidney is transient and does not persist after hatching. The kidney is a major immunoglobulin (Ig) containing tissue during early development as evidenced by increasing numbers of Ig–positive cells.
Minisatellite DNA fingerprints of Atlantic cod (Gadus morhua)
Authors: Dahle G.
Published: April 2005

The human minisatellite probes 33.6 and 33.15 cross–hybridized to Hae III and Hinf I digested cod DNA, revealing complex fragment patterns in both Arctic and coastal cod. The DNA fingerprints were highly polymorphic, individual specific and stable in the germline. The potential applications of multi locus probes in cod research are discussed.
Effect of temperature on the drinking rates of two species of flatfish, flounder and turbot
Authors: Carroll S. , Kelsall C. , Hazon N. , Eddy F. B.
Published: April 2005

Flounders responded to a temperature change of 10° C by increasing drinking rate with a Q10 value of about 1.5 while turbot showed a limited capacity to respond to a similar temperature change. Drinking as an indicator of osmoregulatory performance is well developed in the euryhaline flounder compared to the stenohaline turbot indicating fundamental differences in the physiological response to temperature.
Freshwater larval fish from Lake Trichonis (Greece)
Authors: Economou A. N. , Daoulas Ch. , Psarras Th. , Barbieri‐Tseliki R.
Published: April 2005

The larvae of 15 freshwater fish species from Lake Trichonis (western Greece) are described from field samples and laboratory‐raised fish. Larval morphologies are compared to identify distinguishing characters. The potential utility of these data sets for assessing phylogenetic relationships is discussed.
Food of Iago omanensis, a deep water shark from the northern Red Sea
Authors: Waller G. N. H. , Baranes A.
Published: April 2005

Stomach contents of 252 lago omanensis were examined. Sharks were collected in deep water between 150 and 450 m depth off the Marine Laboratory of Eilat. This species feeds on benthopelagic fishes, deep water cephalopods, crustaceans, benthic molluscs and polychaetes. Cephalopods were the main food of I. omanensis, except during the summer when fishes (mainly myctophids) were ingested in greater quantity. Stomachs also contained terrigenous plant matter, animal remains and large quantities of mud. Prey taxa included two new cephalopod records for the Red Sea.
The spread of furunculosis in salmonids in Norwegian rivers
Authors: Johnsen B. O. , Jensen A. J.
Published: April 2005

Furunculosis was first discovered in a fish farm in Norway in 1964, following the importation of rainbow trout from Denmark. The disease spread to several farms and to wild fish in the River Numedalslågen, occurring there until 1979. It was eradicated at several farms, the last being disinfected in 1969. In 1985, furunculosis was discovered in marine fish farms in Nord‐Trøndelag, following importation of salmon smolts from Scotland. The disease reached Møre og Romsdal in 1988, by which time 32 fish farms were infected in the two counties. By the end of 1992, 550 farms were infected. The disease spread concurrently in natural watercourses, from 22 in 1989, to 74 by the end of 1992. Rapid spread of the disease was associated with several factors including escapes from fish farms, possibly via transport of fish between farms, and natural movement of wild fish in the sea. The disease was not associated with particular physical characteristics in these watercourses, but large aggregations of fish beneath waterfalls combined with high water temperature may trigger disease outbreaks. The ecological consequences of furunculosis are not known. However, some river populations of adult salmon, sea trout and brown trout have suffered. Furunculosis may result in serious negative consequences for populations if a significant number of the brood stock die before spawning.
Reproductive biology and larval development of the terapontid Amniataba caudavittata, including comparisons with the reproductive strategies of other estuarine teleosts in temperate Western Australia
Authors: Potter I. C. , Neira F. J. , Wise B. S. , Wallace J. H.
Published: April 2005

Samples collected monthly from the Swan Estuary between March 1978 and May 1979, together with environmental data for 1977 to 1980, have been used to elucidate various aspects of the reproductive biology of Amniataba caudavittata in this estuary. The gonads of A. caudavittala started to develop rapidly in the spring, when day length, water temperatures and salinities were increasing markedly. Spawning, which occurred mainly towards the top end of the upper estuary, was initiated in November, when water temperatures and salinities in that region were c. 24° C and 9‰, and it peaked in December/January when they were c. IT C and 17%○, Maturity is attained by at least the majority offish at the end of the second and each subsequent year of life. Although some of the larger 1‐year‐old fish attained maturity, this occurred in only one of the two tributary rivers, possibly reflecting differences in the salinity regimes in these rivers. Fecundities ranged from 50 000 in a 150‐mm fish to 705 000 in a 254‐mm fish, with a mean of 310 000. The mature, unfertilized eggs are small and spherical and have a diameter of 560 μm. The larvae are pelagic and characterized by an elongate body, which becomes moderately deep and laterally compressed during development, a short to moderate, tightly‐coiled gut, a distinct gap between the anus and the origin of the anal fin and 25 or 26 myomeres. The development of fins and settlement of A. caudavittata larvae occurs at a smaller size than in the larvae of other terapontid species previously described. The success of A. caudavittata in the Swan Estuary can be attributed in part to its production of very large numbers of eggs at a time when, due to low fresh water discharge and a smait tidal range, conditions in the estuary are relatively stable. Comparisons between the biology of A. caudavittata and that of other abundant teleosts that spawn in south‐western Australian estuaries show that these species exhibit a wide range of reproductive strategies.
The effects of extremely alkaline water (pH 9·5) on rainbow trout gill function and morphology
Authors: Wilkie M. P. , Wood C. M.
Published: April 2005

Rainbow trout that were held under control conditions, at pH8·0, in moderately hard Hamilton tap water, had Cl− and Na+ influx rates (JCLin and JNa, respectively) of 270 and 300 μmol kg−1 h−1, respectively. Exposure to pH 9·5 water led to an immediate 67% decline in JCLin and a 45% reduction in JNain at 0–1 h. Influx rates declined further and by 4–5 h the net decreases in both JCLin and JNain approximated 80%. By 24 h JCLin had recovered to rates not significantly different from those at pH 8·0; while JNain only partially recovered and remained about 50% lower than control measurements through 72 h. The complete recovery of JCLin and partial recovery of JNain may have been related to a fourfold greater branchial chloride cell (CC) fractional surface area observed in rainbow trout exposed to pH 9·5 for 72 h. Ammonia excretion (JAmm) was about 170 μmol N kg−1 h−1 at pH 8·0 but was initially reduced by 90% over the first hour of high pH exposure. JAmm rapidly recovered and by 24 h it had returned to pre‐exposure levels. This recovery tended to parallel the partial recovery of JNain. However, subsequent addition of amiloride (10−4M) to the water at 75 h led to no change in JAmm, despite a 50% reduction in JNain. Thus, it does not appear that there is a linkage between Na+ influx and the recovery of ammonia excretion under highly alkaline conditions.
Dispersal of wild and domestic masu salmon fry (Oncorhynchus masou) in an artificial channel
Authors: Nagata M. , Nakajima M. , Fujiwara M.
Published: April 2005

The day and night pattern of upstream and downstream dispersal of masu salmon fry of wild and domestic origin was compared in artificial channels (45 m long), for two ages of planting: unfed alevins and eyed eggs. Early dispersal was important for the wild stock (48–50%) compared with the domestic one (16–36%). More wild fry moved downstream than upstream, and more domestic fry dispersed upstream. Upstream movement in wild and domestic fry was more active by day than by night, except for wild fry planted as eyed eggs, where upstream migration was higher at night. In contrast, downstream movement in wild and domestic fry was more common by night than by day, but daylight catches were not negligible for the wild stock.
Behaviour and swimming performance of elvers of the American eel, Anguitta rostrata, in an experimental flume
Authors: Barbin G. P. , Krueger W. H.
Published: April 2005

Migrating elvers of the American eel, Anguilla rosirata, were examined in an experimental flume to determine the effect of water speed and presence of substrate on swimming performance. Use of the substrate as a resting area between movements increased with increasing water speed. The number of elvers moving in the boundary layer above the substrate was significantly greater than those moving in the water column. Swimming speed in the water column and along the substrate increased with water speed. Rate of progress over ground in the water column and boundary layer increased slightly with water speed initially, but subsequently declined in the boundary layer. Overall, swimming speed increased linearly with increasing water speed and net upstream progress remained constant with increasing water speed. Use of the boundary layer probably was restricted by the thickness of the layer as a function of water speed. The boundary layer should be used to maximize distance and minimize energy expense when migrating upstream. Elvers appear to use substrate to avoid free stream velocities and not as a medium for movement. Fifty per cent of all elvers tested in a chamber without substrate, which had no resting places, were unable to swim; thus migrations may be limited by the need to rest. The potential migration rate was estimated to approach 100m per day, based on movements in the substrate chamber.
The functional grazing response of a phytoplanktivorous fish Oreochromis mloticus to mixtures of toxic and non‐toxicstrains of the cyanobacterium Microcystis aeruginosa
Authors: Keshavanath P. , Beveridge M. C. M. , Baird D. J. , Lawton L. A. , Nimmo A. , Codd G. A.
Published: April 2005

Small (10 g) tilapia (Oreochromis niloticus) were exposed to pure and mixed populations of toxic and non‐toxic strains of the cyanobacterium Microcystis aeruginosa (100% toxic, 50% toxic, 25% toxic, 0% toxic) at two particle concentrations (1 × 106 and 5 × 10sparticles ml−1). At both concentrations there was a progressive decrease in grazing rate as the percentage of toxic cells increased. Differences in opercular beat rates, and hence the volumes of water passed over the gills, were also recorded among treatments, opercular beat rates decreasing as the percentage of toxic cells increased. Although in all treatment groups with toxic cells present, the medium had detectable levels (>250 ng I−1) of extracellular microcystin‐LR toxin present, grazing was correlated with particle‐bound rather than extracellular levels.
Fatty acid content of the dorsal muscle—an indicator of fat quality in freshwater fish
Authors: Ahlgren G. , Blomqvist P. , Boberg M. , Gustafsson I.‐B.
Published: April 2005

In 56 samples of freshwater fish, most were low in fat, ≤ 5% of dry weight (D.W.), and the sum of all fatty acids (ΣFA) was about 2% of D.W. Trout, whitefish, and grayling had the highest content of the long‐chained FA. of ω3 type, EPA and DHA (1·7–2·6% of D.W.). Two large, low‐fat pikes with ΣFA of about12–3% of D.W. and a medium‐fat whitefish had the highest ω3/ω6 ratios, 8–9, whereas the fattiest fishes, eels from two lakes and the Baltic (ΣFA =17–26% of D.W.) had lower ω3/ω6 ratios, 1·1–1·8 (ω3 and ω6 FA are two important series of FA). The results indicate that ΣA controls the content of saturated FA (SAFA) and monounsaturated FA (MUFA), whereas the polyunsaturated FA (PUFA) was independent of ΣFA after a break point of about 10%ΣFA of D.W. The P/S ratio (PUFA/SAFA) and the PUFA/ΣFA ratio decreased with increased ΣFA, whereas the ω3/ω6 ratio showed no clear correlation to ΣFA.

The difference in fatty acid patterns lay between low‐fat and high‐fat fishes, rather than between marine and freshwater fishes. The variation, both within and between species of the separate FA is small in fish with similar ΣFA content. Also, low‐fat and medium‐fat fishes tend to be more dietarily favourable than high‐fat fishes, when considering the latest criteria for high nutritional value to humans.

Abbreviations used in the text: FA, fatty acids; ΣFA, sum of all FA; AA, arachidonic acid (20 : 4ω6); EPA, eicosapentaenoic acid (20 : 5ω3); DHA, docosahexaenoic acid (22 : 6ω3); SAFA, saturated fatty acids; MUFA, monounsaturated fatty acids; PUFA, polyunsaturated fatty acids; D.W., dry weight; F.W. fresh weight; CV, coefficient of variation; ω3 FA, series of PUFA with the first double bond located at carbon number 3; ω6 FA, series of PUFA with the first double bond located at carbon number 6. The fatty acids are described by three numbers, x:ywz, where x=number of carbon atoms, y=number of double bonds, and z=position of the first double bond counted from the methyl end of the molecule.
Application of semi‐quantitative electrofishing to juvenile salmonid stock surveys
Authors: Crozier W. W. , Kennedy G. J. A.
Published: April 2005

A semi‐quantitative electrofishing technique is described, which has applications for assessing distribution and densities of 0+ salmonids in streams. Linear regressions of logarithmically‐transformed data satisfactorily described the relationship between numbers of 0+ Atlantic salmon (Salmo salar L.) and 0+ brown trout (Salmo trutta L.) captured in a standard 5 min fishing and quantitative population estimates obtained using a commonly used method. Applications of the semi‐quantitative technique to management are discussed and a categorization system proposed.
Heavy infection of Diodon hystrix by the copepod Peniculisa wilsoni (Siphonostomatoida, Pennellidae
Authors: Chandran A. , Natarajan P.
Published: April 2005

Heavy infections of the copepod Peniculisa wilsoni are reported from the fins of Diodon hystrix.
The effect of high dietary zinc on trypsin activity in carp (Cyprinus carpio)
Authors: Brafield A. E. , Koodie A. V.
Published: April 2005

Carp fed pellets containing a range of zinc concentrations showed a significant increase in trypsin activity in the intestine with increasing zinc in the diet.
The use of a perfused, whole‐body preparation to measure the branchial and intestinal influx of 137‐caesium in the rainbow trout (Oncorhynchus mykiss)
Authors: Morgan I. J. , Tytler P. , Bell M. V.
Published: April 2005

The branchial and intestinal influx of caesium (Cs) in the rainbow trout (Oncorhynchus mykiss) were measured using a perfused whole‐body preparation. The branchial influx of Cs was small, 0–31 μmoles kg−1 h−1 at an external concentration of 1 mm. Branchial Cs influx was saturable, with a Km of 1–92 mm and a Jmax of l.05μmoles kg−1 h−1. Intestinal Cs influx was not saturable, but was directly proportional to the mucosal Cs concentration. Intestinal Cs influx was approximately 10–40 times greater than branchial Cs influx over a wide range of external Cs concentrations. These results are discussed with respect to mechanisms of Cs uptake and to the relative accumulation of radiocaesium from water and food in the environment.
Effects of experimental anaemia on intra‐erythrocytic phosphate levels in rainbow trout, Oncorhynchus mykiss
Authors: Val Adalberto L. , Mazur Carl F. , de Salvo‐Souza Roberto H. , Iwama George K.
Published: April 2005

The concentrations of intra‐erythrocytic adenylates (ATP, ADP and AMP) and guanylates (GTP, GDP and GMP) were determined in rainbow trout subjected to 10% blood removal every 12 h for 96 h. Haemoglobin concentration, [Hb], decreased from 6·043±0·617 to 0·957 ± 0·195 g dl−1. This decrease in [Hb] was followed by a continuous increase in total organic phosphates, e.g. adenylates plus guanylates. Intra‐erythrocytic NTP (ATP plus GTP) levels increased significantly after 48 h when haemoglobin concentration was 2·427 ± 0·256 g dl−1. Although a significant increase in GDP levels in animals with [Hb] less than 1·677 ± 0·235 g dl−1 was observed, the general increase in guanylate level was mainly due to the GMP which increased about 85‐fold during the experimental period. It is suggested that the erythrocytes of anaemic rainbow trout have the capacity to increase NTP/Hb4 ratios which may represent an advantage for anaemic fish.
Genic diversity in Red River pupfish Cyprinodon rubrofluviatilis (Atheriniformes: Cyprinodontidae) and its implications for the conservation genetics of the species
Authors: Ashbaugh Nicholas A. , Echelle Anthony A. , Echelle Alice F.
Published: April 2005

Starch gel electrophoresis of proteins was used to study geographic variation at 26 gene loci in the Red River pupfish (Cyprinodon rubrofluviatílís), a species restricted to west Texas and Oklahoma. Marked differences were detected between populations in the Red and Brazos river drainages, with fixed or nearly fixed differences occurring at five gene loci. In addition, mean heterozygosity was uniformly high for the Red River form (H̄= 0·076–0·101) while samples of the Brazos River form were genetically depauperate (H̄=0·00–0·017). Introduced populations in the South Canadian and Colorado river drainages appear to have been derived from the Red River drainage. The presence of alleles diagnostic of the Red and Brazos river forms supports the suggestion from previous work that they may represent cryptic species. Regardless of taxonomy, however, the presence of two genetically distinct forms must be taken into consideration by those concerned with maintenance of biotic diversity.
Pattern formation of the ‘Tilapia mark’ in the tilapia fish, Oreochromis mossambicus
Authors: Lim K. E. K. , Lam N. H. , Phang V. P. E. , Lim T. M.
Published: April 2005

The dorsal fin of the larval and juvenile Oreochromis mossambicus exhibits a unique black spot known as the ‘Tilapia mark’. We traced its development and found that it occupied a specific position in the dorsal fin bounded by rays 15 and 20. Ablation experiments carried out on the larval dorsal fin showed that this spot region constituted a developmental positional field. This positional field in the fin could regenerate and re‐establish the spot pattern despite repeated perturbation. The re‐establishment of spot was not simply due to fin injury since ablation of the non‐spotted region of the dorsal and the tail fin did not result in aggregation of melanophores. We propose that that‘Tilapia mark’ is a result of positional information in operation.
Epinephrine, norepinephrine, and cortisol concentrations in cannulated seawater‐acclimated rainbow trout (Oncorhynchus mykiss) following black‐box confinement and epinephrine injection
Authors: Gamperl A. K. , Vijayan M. M. , Boutilier R. G.
Published: April 2005

The present study investigates the effect of cannulation and chronic‘black‐box’ confinement, as well as epinephrine administration (4–0 μg kg−1), on the degree and time‐course of alterations in trout (Oncorhynchus mykiss) catecholamine and cortisol concentrations. Plasma cortisol concentrations in seawater trout acclimated to 3–6° C reached 104 ng ml−1 1 day after cannulation/confinement and remained elevated above resting levels (8 ng ml−1) until 6 days post‐confinement. Although plasma epinephrine and norepinephrine generally declined over the period of confinement (day 1 approx. 12 nM; day 7 approx. 6 nM), norepinephrine titres were usually higher and more variable. Epinephrine injection caused elevations in plasma epinephrine levels but not in norepinephrine levels; epinephrine titres reaching 107 ± 26 nM (range 65–238 nM) at 2 min post‐injection and returning to pre‐injection levels by 30 min post‐injection. Plasma cortisol increased by 20 ng ml−1 following epinephrine administration. Based on the time‐course for post‐confinement alterations in plasma cortisol, it appears that up to a week may be required before cannulated fish are completely acclimated to ‘black‐box’ confinement. The findings suggest that meaningful results from experiments utilizing epinephrine injection and ‘black‐box confinement are contingent upon: (1) knowledge of circulating epinephrine levels shortly after injection (i.e. within 2 min post‐injection); and (2) an experimental design that takes into account the elevated cortisol titres that are inherent with cannulation/confinement and epinephrine injection.
Activity and swimming speed at time of first feeding of halibut (Hippoglossus hippoglossus) larvae
Authors: Skiftesvik A. B. , Bergh ø. , Opstad I.
Published: April 2005

Atlantic halibut larvae show an increase in activity, together with a decrease in swimming speed during active periods, occurring from day 26 onwards, which corresponds approximately to 50% yolk absorption.
Further data on the reproduction and larval development of Knipowitschia caucasica (Gobiidae)
Authors: Economou A. N. , Daoulas C. , Psarras T. , Barbihri‐Tseliki R.
Published: April 2005

The courting spawning and parental care behaviours of Knipowitschia caucasica (Kawrajsky) in an aquarium are described and the earliest stages of ontogenetic development are illustrated.
The effects of repeated physical stress or fasting on catccholamine storage and release in the rainbow trout, Oncorhynchus mykiss
Authors: Reid Steve G. , Furimsky Marosh , Perry Steve F.
Published: April 2005

Rainbow trout, Oncorhynchus mykiss, were subjected to either physical stress (twice daily chasing to exhaustion for 5 days) or a period of 2 months of fasting. Following these treatments, the levels of catecholamines, adrenaline and noradrenaline, stored within the kidney and posterior cardinal vein (PCV) were determined. The ability of the catecholamine‐storing chromaffin cells to release catecholamines in response to cholinergic stimulation was measured using an in situ saline‐perfused PCV preparation.

In the physically stressed fish, the concentration (μg catecholamine g−1 tissue) of noradrenaline within the anterior and middle thirds of the kidney increased; the concentration of adrenaline was unchanged in all tissues. The content (μg) of noradrenaline or adrenaline, within the various tissues, was similar in both groups of fish with the exception of a higher noradrenaline content in the middle third of the kidney in the physically stressed fish. The total catecholamine content (μg catecholamine) of these tissues (kidney+PCV) was unaffected by physical stress.

With the exception of a lower concentration of adrenaline in the middle third of the kidney, the concentrations of catecholamines were unaffected by fasting. There was a trend towards a greater content (μg) of noradrenaline within all of the tissue regions of the fed fish, however, a significant difference was only observed in the anterior third of the kidney. The content of adrenaline in the fed fish was greater in all regions of the kidney as well as the middle third of the PCV. The total catecholamine content (kidney + PCV) was lower in the fasted fish owing to significantly lower PCV and kidney masses.

Prolonged physical stress caused a decrease in the responsiveness of the chromaffin cells to the cholinoceptor agonist carbachol (10−8 to 10−4mol). The ED50 (the dose of carbachol required to elicit a half maximal response) for catecholamine release was 0·96 ± 10−6mol carbachol in the physically stressed fish and 0·84 ± 10−7 in the control fish. Fasting did not alter the pattern of catecholamine release. The ED50 values were 0·96 ± 10−7 and 1·24 ± 10−7 mol for fasted and fed fish, respectively. Thus, a physical stress affected both catecholamine storage and release whereas fasting affected only storage and not the release process.
Racial differences in eggs and juveniles of Windermere charr, Salvelinus alpinus
Authors: Baroudy E. , Elliott J. M.
Published: April 2005

At least four races of charr occur in Windermere, the largest natural lake in England: north basin and south basin autumn spawners, north basin and south basin spring spawners. This study examines racial differences between eggs and juveniles, and relates juvenile size and survival to egg size. There were no major differences between races for egg incubation times and the percentage of eggs hatching successfully, the latter being high (mean values 76–96%) with a negligible proportion of abnormal alevins (<0.8%). Although there were no significant differences in the lengths of the female parents, both eggs and alevins were significantly larger for the autumn spawners than the spring spawners. Size differences in alevins, especially live weight, were positively related to egg size but not female parent size. Mean percentage survival for juveniles attaining the independent feeding stage was higher for the progeny of autumn spawners (32%) than spring spawners (3%). Racial differences in the egg and alevin stages therefore appear to have a significant effect on subsequent survival, and could be ultimately responsible for the relatively small proportion of spring spawners (only 4–6%) in the Windermere population of charr.
Individual recognition of juvenile salmonids using melanophore patterns
Authors: Garcia de Leaniz Carlos , Fraser Neil , Mikheev Victor , Huntingford Felicity
Published: April 2005

This article describes two small scale experiments designed to test whether variation in melanophore patterns could be used to identify individual juvenile salmonids that are too small for conventional marking methods. Three independent observers were able to identify 30 individual 0+ Atlantic salmon (Salmo solar) parr from photographs taken over an 8‐week period with 100% accuracy, on the basis of patterns of melanophores in the region of the eye and jaw. Counts of the number of melanophores in two particularly variable regions of the head of 14 newly‐emerged brown trout (Salmo trutta) from photographs of the same individuals taken on different occasions were strongly correlated. Eighty‐four per cent of the fry were correctly identified on the basis of spot number alone, without any reference to their patterns. Thus a combination of the number and position of head melanophores can be used for recognition of relatively large samples of very young salmonids. Problems with, and potential applications of this method are discussed.
Effect of reward level on individual variability in demand feeding activity and growth rate in Arctic charr and rainbow trout
Authors: Brännäs E. , Alanärä A.
Published: April 2005

Groups of Arctic charr and rainbow trout were fed by using demand feeders and their individual trigger actuations registered with a PIT‐tag (Passive Integrated Transponder) system. Food was supplied at two reward levels, low and high, to five replicate groups of each species for 21 to 27 days. The reward level was defined as the amount of food obtained in response to a single trigger actuation. The effects of reward level on individual demand feeding activity and growth rale were assessed.

As a result of high demand feeding activity, the daily food rations for trout were in excess of their needs at both reward levels. This can be ascribed to the fact that they compensated a low reward level by increasing their bite activity. In contrast, demand feeding activity in charr did not differ significantly between reward levels. Instead, resulting food rations were limiting and excessive, at low and high reward levels, respectively. The variation in bite activity between individuals (measured as their proportional contribution to the total number of trigger actuations within a group) for charr was significantly higher in the low‐reward treatment than in the high‐reward level. For trout, the variation in bite activity did not differ significantly between treatments. Differences in response to reward level are suggested to be due to the fact that the social hierarchy is weaker in trout than in charr; i.e. the differences in bite activity between dominant and non‐dominant individuals are smaller in trout. At both reward levels, the benefit of being dominant, measured in terms of growth rate was significant for charr but non‐significant for trout.
Survival, activity and feeding ability of Baltic cod (Gadus morhua) yolk‐sac larvae at different salinities
Authors: Nissling Anders , Solemdal Per , Svensson Mikael , Westin Lars
Published: April 2005

Due to unfavourable conditions (declines in salinity and water oxygen content) in the spawning areas, there has been a considerable decrease in the Baltic cod stock since the beginning of the 1980s, and consequently a decrease in catches. In order to examine the feasibility of introducing yolk‐sac larvae in areas of low salinity to improve the stock, laboratory experiments were performed on the effects of salinity on the survival, level of activity and feeding ability of larvae. Yolk‐sac larvae from spawning cod caught off northern Gotland, Sweden, were exposed to four different salinities: 10 and 15%○ (salinities of the main spawning areas); and 5 and 7%○ (salinities in the Bothnian Sea and the Baltic proper respectively).

The survival of yolk‐sac larvae was high at all salinities, even though there was an indication of higher mortality at low salinities in less viable larval groups. No differences were found in swimming speed or feeding ability at the four salinities, but a significant difference in vertical distribution was recorded. There were significant differences in survival, vertical distribution and feeding ability among larval groups, which indicates that larval quality or viability is of greater importance for larval survival than salinity, in the range of 5–15%○.
Juvenile Atlantic salmon in the Varzuga River (White Sea Basin)
Authors: Kazakov R. V.
Published: April 2005

In the Varzuga River (Kola Peninsula), juvenile Atlantic salmon occur at a high mean density of 1·1 individuals per m2, with a relatively low growth rate, reaching c. 8 g at age 3. They migrate to sea at ages 2–4 before they are fully silvered. Mortality is not high and the fish forage in the estuary where they grow fast and acclimate to the pelagic and high salinity habitat.
An electrophysiological study on the effects of pH on olfaction in mature male Atlantic salmon (Salmo salar) parr
Authors: Moore A.
Published: April 2005

The olfactory responses of mature male Atlantic salmon (Salmo salar L.) parr to known odorants were studied after exposure of the olfactory epithelia to water of varying pH. Electrophysiological recordings from the olfactory epithelia indicated that the responses of fish to both testosterone and urine from ovulated female Atlantic salmon were significantly reduced at pH 5·5 and 4·5 and abolished at pH 3·5. Concentration response studies indicated that at pH 5·5 and 6·5 significantly higher concentrations of testosterone and urine were required to produce the same amplitude responses as controls. Both testosterone and urine have previously been shown to be important chemical cues eliciting behavioural and physiological responses in Atlantic salmon. The results are therefore discussed in relation to the possible sublethal effects of acidification on reproduction and behaviour of Atlantic salmon and the effects on salmonid stocks.
Niche separation between colonizing and indigenous goatfish (Mullidae) along the Mediterranean coast of Israel
Authors: Golani D.
Published: April 2005

The present study assesses the resource partitioning between two Red Sea colonizers, the goldband goatfish Upeneus moluccensis and the brownband goatfish U. pori, and the two indigenous Mediterranean goatfishes, the red mullet Mullus barbatus and the striped mullet M. surmuletus, along the Mediterranean coast of Israel.

Niche separation was studied along three axes: habitat selection, feeding habits and spawning season. Habitat selection is the most significant parameter separating the species. The two colonizing species occupy a shallow habitat, U. pori dominating the primarily sandy bottom at 20–30 m and U. moluccensis at 40–50 m, at which depth the sea bottom becomes increasingly silty. Of the two indigenous species, M. barbatus is dominant in depths below 55 m, while M. surmuletus appears at low abundance in all depths.

Niche separation by feeding habits is much less evident. All four species feed primarily on macrurid crustaceans and thus the values of diet overlap are rather high (0·666≤T≤0·928). Prey size is not an important factor in niche separation. Young fishes (S.L>,115 mm) of all four species feed upon prey of similar size (20–160 mg). Among older individuals (S.L.>115 mm) three species continue to feed upon the same size prey, while U. moluccensis feeds upon considerably larger prey (600–2200 mg).

The difference between the spawning seasons of the colonizing vs indigenous species and consequent timing of benthic settling may contribute to niche separation.

The results of this study suggest that success in colonization by Red Sea goatfish may be due to the existence of unexploited niches in the eastern Mediterranean ecosystem.
Volatile fatty acids in the hindguts of herbivorous fishes from temperate and tropical marine waters
Authors: Kandel J. S. , Horn M. H. , Van Antwerp W.
Published: April 2005

Relative volatile fatty acid composition in the hindgut of four seaweed‐eating fishes ranged from acetate only in the cool temperate species to a full array of six types in the warm temperate species and the two tropical/subtropical species.
A reappraisal of activity metabolism in Atlantic cod (Gadus morhua)
Authors: Tang Y. , Nelson J. A. , Reidy S. P. , Kerr S. R. , Boutilier R. G.
Published: April 2005

Atlantic cod (Gadus morhua) were forced to swim in a swim tunnel respirometer until fatigued; oxygen consumption rate (ṀO2) was measured during swimming at incremental speeds until the fish was exhausted and during recovery from exhaustion. Maximal oxygen consumption (ṀO2max) occurred during maximal activity as has been found for other fish species, but at odds with the current paradigm for Atlantic cod. Earlier experiments had drawn the conclusion that ṀO2max in Atlantic cod occurs during recovery from exhaustive exercise. We found no support for this paradigm in our experiments and we propose that the respiratory physiology of Atlantic cod is not unlike that of other fishes.
The age, growth and reproduction of Chondrostoma polylepis willkommi in a seasonal stream in the Guadalquivir River basin (southern Spain)
Authors: Herrera M. , Fernández‐Delgado C.
Published: April 2005

The age, growth and reproduction of Chondrostoma polylepis willkommi, an endemic cyprinid from the Iberian Peninsula, was studied for 2 years in a seasonal stream in the Guadalquivir River basin. Annual growth was low. Maximum ages observed were 5+ in males and 7+ in females. There was no significant difference in growth between sexes. Seasonal growth period started in May and continued for 2 to 6 months depending on age. The mean lengths of 1 + and 2+ age‐groups decreased once the growth period had finished, probably related to reproductive stress and adverse ecological conditions, and this could explain the occurrence of Rosa Lee's phenomenon. Both sexes matured at the end of their second year of life (1+). There was a significant difference from 1: 1 in the overall sex ratio of 334 males to 464 females. Reproductive period started in March and lasted until May. Ch. p. willkommi was a multiple spawner that released two batches of eggs per female each year. The regression between fecundity (F) and fork length (l., mm) was: F=6.20 103 L.2.78. In females from age 2 + onwards, relative annual investment in somatic growth and reproduction was equivalent, implying that the same energy was allocated to reproduction as to maintenance/growth. Compared with other Ch. polylepis populations, the life‐history patterns of this population, located in a small and seasonal stream in a southern latitude, were characterized by a low annual growth, a trade‐off between reproduction and growth/maintenance, early maturity, low number of age‐groups and high fecundity from multiple spawnings.
Diel variability in catch rate of juvenile flatfish on two small nursery grounds (Port Erin Bay, Isle of Man and Porto Pirn Bay, Faial, Azores)
Authors: Nash R. D. M. , Santos R. S. , Geffen A. J. , Hughes G. , Ellis T. R.
Published: April 2005

Variation in beach seine catches was examined in two juvenile flatfish populations (Port Erin, Isle of Man and Porto Pirn, Azores) to determine the importance of diel cycles while controlling for tidal rhythmicity. At Port Erin sampling was undertaken at each low water on consecutive days over a 2‐week period in May/June and September 1991. There was no periodicity in the catches of plaice (Pleuronectes platessa) in May/June, but in September catches were higher at night. Other flatfish species (Limanda limanda, Pleuronectes flesus, Scophthalmus maximus and S. rhombus) sampled at Port Erin were nocturnal. At Porto Pirn, Azores, fish were sampled over 24 h each month from July 1989 to June 1990 and at each low water over a 2‐week period in July 1991. The only flatfish species present was Bothuspodas, which had a diurnal pattern in catches over a 1‐year period. Sampling at low water in July gave high catches at both midnight and midday.
Pronounced genetic structure of mitochondrial DNA among populations of the circumglobally distributed grey mullet (Mugil cephalus)
Authors: Crosetti D. , Nelson W. S. , Avise J. C.
Published: April 2005

Mitochondrial (ml) DNA genotypes of grey mullet (Mugil cephalus) from ocean basins around the world were analysed to estimate the amount of genetic differentiation in this cosmopolitan but mostly coastally‐restricted species. Extensive genetic diversity was observed. Among 115 specimens from nine locales, 26 different haplotypes were detected using a battery of 13 restriction endonucleases. In phenetic analyses, these haplotypes grouped into seven distinct clusters whose members were in almost perfect accord with the geographic sources of the samples. Thus contemporary gene flow between the widespread collection locales must be absent or nearly so. Results contrast with the relative uniformity in mtDNA composition previously reported for populations of some circumglobally distributed pelagic fishes, and demonstrate that certain marine fishes with cosmopolitan distributions can exhibit pronounced population genetic structure even in the face of morphological conservatism.
Morphology, body size and behaviour of recently‐metamorphosed sea lampreys, Petromyzon marinus, from the lower River Severn, and their relevance to the onset of parasitic feeding
Authors: Bird D. J. , Potter I. C. , Hardisty M. W. , Baker B. I.
Published: April 2005

Several hundred recently‐metamorphosed Petromyzon marinus were caught during heavy freshwater discharge in the River Severn on the night of 30 November/1 December 1988. The total lengths of a subsample of 42 males and 82 females ranged from 155 to 218 mm, with a mean of 182 mm in both sexes. The buccal funnel, eyes, fins and the teeth on the suctorial disc and tongue‐like piston were very well‐developed. When placed in full‐strength sea water, the lampreys fed on bass (Dicentrarchus labrax), leaving prominent scars on these hosts. The morphology, body size and time of capture of the River Severn sea lampreys provide very strong circumstantial evidence that these lampreys had been feeding for some weeks. Since they were caught when moving downstream and were capable of feeding in sea water, they were presumably about to begin their parasitic marine life.
Drinking and water absorption by the larvae of herring (Clupea harengus) and turbot (Scophthalmus maximus)
Authors: Tytler P. , Ireland J.
Published: April 2005

The efficiencies of water absorption from the guts of the larvae of herring (Clupea harengus L.) and turbot (Scophthalmus maximus L.) were estimated by two methods, The first method was based on the differences in the rates of accumulation, by drinking, and clearance from the gut of radiolabelled inert markers. The second method used the equilibrium level of radioactivity in the larvae to measure the concentration of the markers in the gut above background as water is absorbed from the gut. Water absorption efficiencies for herring larvae drinking sea water were estimated to be 77% using both methods. When external salinity was reduced to 50% sea water, drinking rates and water absorption efficiency in herring larvae fell substantially.

Estimates of water absorption efficiency of seawater‐adapted turbot larvae were similar (71–84%) to that of herring using both methods. Although temperature had a marked effect on both the rate of drinking and water absorption, there was no significant thermal effect on the efficiency of absorption from the guts of turbot larvae. The limitations of the techniques and the implications of the estimates in terms of water balance in fish larvae are discussed.
Dynamics of excretion of 17α,20β‐dihydroxy‐4‐pregnen‐3‐one 20‐sulphate, and of the glucuronides of testosterone and 17β‐oestradiol, by urine of reproductively mature male and female rainbow trout (Oncorhynchus myklss)
Authors: Scott A. P. , Liley N. R.
Published: April 2005

Levels of sulphated 17α20β‐dihydroxy‐4‐pregnen‐3‐one (17,20β‐P; the oocyte maturation inducing steroid) in blood plasmas of sexually mature male and female rainbow trout Oncorhynchus mykiss, were very low in comparison to those of the free steroid. However, relatively large amounts were found in urine of both sexes.

Catheters were inserted into the urinary bladders of unovulated and ovulated females and of ripe‐running males, and the fish then placed in spawning channels. Three‐hourly urine samples were collected between 09.00 and 18.00 hours and then a 15‐h sample between 18.00 and 09.00 hours the next morning. Measurements were made of 17,20β‐P‐sulphale, testosterone glucuronide (T‐G) and 17β‐oestradiol glucuronide (E2‐G). In females, the highest rates of excretion of E2‐G, T‐G and 17,20β‐P‐sulphate were found in unovulated, ovulating and ovulated females, respectively. The rates of excretion of 17,20β‐P‐sulphate, T‐G and E2‐G in ovulated females were unaffected by the presence of a male. id males, however, there was a sharp increase in the rate of excretion of 17,20β‐P‐suiphate and T‐G in fish which were paired with an ovutated (nesting) female. A similar increase was found in males injected with male trout pituitary extract.