bluuebunny/crossref_metadata_2025 huggingface dataset:
Prolonged‐release gonadotrophin‐releasing hormone analogue implants enhance oocyte final maturation and ovulation, and increase plasma concentrations of sulphated C21 steroids in North Sea plaice
Authors: Scott A. P. , Witthames P. R. , Vermeirssen E. L. M. , Carolsfeld J.
Published: April 2005

Reproductively mature female plaice were implanted with or without 50 μg of gonadotrophin‐releasing hormone analogue (GnRHa), suspended in either coconut oil or methacrylate resin. The weight of the GnRHa‐treated fish increased significantly (due to hydration of the oocytes) and reached a peak between 10 and 14 days. The fish produced several batches of eggs, which were consistently bigger than those produced by control fish. Plasma concentrations of free 17β‐oestradiol and glucuronidated testosterone rose briefly (4 days) in response to the GnRHa, but then fell continuously till the end of the experiment (20 days). Plasma concentrations of sulphated 5β‐pregnane‐3α,17,20β‐triol and 5β‐pregnane‐3β,17,20β‐triol (which are putative metabolites of 17,20β‐dihydroxy‐4‐pregnen‐3‐one, the oocyte maturation‐inducing steroid) increased significantly at 4 days and reached a peak between 12 and 16 days. Concentrations were still very elevated on day 20. Plasma concentrations of sulphated 3α,17,21‐trihydroxy‐5β‐pregnan‐20‐one showed a slight increase on day 4 but did not change thereafter. There was a highly significant difference in the amounts of GnRHa released into the bloodstream by the two methods of administration on day 4. However, this was not matched by significant differences in the concentrations of any of the steroids.
Sperm and milt characteristics and male v. female gametic investment in the Caribbean reef fish, Thalassoma bifasciatum
Authors: Schärer L. , Robertson D. R.
Published: April 2005

Individual sperm cells produced by two male morphs of the bluehead wrasse Thalassoma bifasciatum did not differ in size (i.e. cell volume). Initial phase (IP) males (high sperm competition) had a 60% higher sperm concentration in their milt than did terminal phase (TP) males (low sperm competition), which may reflect differences in how accurately the two male morphs need to allocate sperm to their spawns. The energy density of milt was about 16% lower than that of eggs. Estimates of gametic energy investment based on (a) the difference in testis weights between the beginning and the end of the spawning period and (b) the number of sperm released in natural spawns (determined in other studies), suggested that, on a daily basis, IP males invest about 65% of that of females. Estimates based on stripping milt from IP males at the beginning and the end of the spawning period, however, indicated that their daily energy investment in gamete production is about 10% of that of females Gametic investment by TP males is lower than that by both IP males and females.
Adaptive and evolutionary significance of a reproductive thermal threshold in Barbus barbus
Authors: Baras E. , Philippart J. C.
Published: April 2005

From 1989 to 1996, barbel in the River Ourthe started spawning under variable environmental conditions, except for water temperature. Each year, spawning was initiated when water daily minimum temperature reached or exceeded 13·5° C. Any decrease of temperature below this value later in the spawning period caused spawning to be suspended. Analyses of offspring growth provided evidence that 13·5° C was the value below which 0+ barbel stop growing. It was hypothesized that barbel trade off the lower initial probability of survival against a larger size at the onset of winter. To test empirically for this hypothesis, the adequacy of alternative—theoretical—strategies associated with other thermal thresholds (12, 15·0, 17·1 and 20·2° C) was modelled with respect to: (1) the feasibility of spawning (inhibition of sexual maturation by a decreasing photoperiod); (2) the impact of the temperature on embryonic development; (3) the effect of water level variations on the integrity of spawning grounds until the emergence of larvae; (4) the size of the offspring at the onset of winter. On an 8‐year (1989–1996) average, the present spawning strategy would have produced a higher recruitment than alternative strategies (relative adequacy of 33·23, 85·64, 93·17 and 17·62%, respectively). However, alternative strategies would have produced better annual scores on five of eight occasions in the River Ourthe environment, and a better overall score in environments 1·5 or 3·5° C warmer than now. The consistency of the thermal threshold over years, despite a low selection pressure by the environment, was interpreted as the expression of a phenotypic mechanism (thermal homing) promoting the selection of the lowest efficient thermal threshold, and enabling breeders to relay to the next generation some form of thermal stability in a variable environment.
Subordination stress in Nile tilapia and its effect on plasma lysozyme activity
Authors: Caruso D. , Lazard J.
Published: April 2005

Dominant Nile tilapia had significantly higher lysozyme activity than did subordinate fishes (α=0·05). Plasma lysozyme level was not correlated with sex, parental origin, rearing length, weight, condition factor or rearing density.
The chromosomal complement of Aphia minuta, a paedomorphic goby
Authors: Caputo V. , Caniglia M. L. , Machella N.
Published: April 2005

The diploid complement of the paedomorphic goby Aphia minuta ranged from 44 to 41 due to Robertsonian fusions (fundamental number=44). Data on spermatogenesis suggest that structural heterozygotes are fertile and that these chromosomal changes are not involved in a speciation process.
Use of female nest characteristics in the sexual behaviour of male sockeye salmon
Authors: HAMON T. R. , FOOTE†§ C. J. , Brown G. S.
Published: April 2005

On three island beaches in Iliamna Lake, Alaska, large numbers of male sockeye salmon gathered and spawned in artificial excavations that mimicked a female's nest immediately prior to spawning, while apparently ignoring the control site. The number of males attracted was correlated positively with changes in the operational sex ratio. In contrast, on the mainland beach examined, no reaction to the artificial nests was apparent. The results are discussed in terms of mate searching behaviour by males, the duration of the spawning period, and associated selection pressures on males to use characteristics of their environment that provide information on availability of females.
Between‐year variation in community structure and biomass–size distributions of benthic lake fish communities
Authors: Holmgren K.
Published: April 2005

The benthic fish communities of 26 Swedish lakes were monitored annually with multi‐mesh gillnets in a standardized way in the years 1994–1997. No major environmental changes (e.g. in nutrient level or acidity) occurred within the lakes during the 4 years of study. In most of the lakes, the between‐year variation of biomass (per unit of effort) was close to the sampling precision, and biomass was usually less variable than abundance. Median values of lakespecific indices of variance compensation indicated no general covariance of biomass between species, but a tendency for positive covariance between size classes. This indicates that the benthic fish communities of small to intermediate‐sized Swedish lakes most often show low between‐year variation in total biomass of fish older than 0+, and that their biomass–size distributions are not, in general, shaped by periodic strong year‐classes of keystone species. In a few individual lakes, density compensation was indicated as complementary proportions of a pair of species or size classes that made major contributions to the total biomass.
Taxonomic relationships between four species of the Mullidae family revealed by three genetic methods: allozymes, random amplified polymorpic DNA and mitochondrial DNA
Authors: Mamuris Z. , Stamatis C. , Bani M. , Triantaphyllidis C.
Published: April 2005

Genetic distances were lower between Upeneus moluccensis and Pseudopeneus prayensis than between those species and Mullus barbatus and Mullus surmuletus. However, for allozymes, the two Mullus species were found genetically more distinct from U. moluccensis than from P. prayensis, but RAPD and mtDNA analysis showed the opposite. RAPDs revealed less interspecific divergence compared with allozymes and the results they produced were more consistent with mtDNA analysis. Although RAPDs did not add any supplementary taxonomic information, they proved valuable tools for quick and reliable species discrimination compared with allozymes and mtDNA.
Histochemistry of the development of the digestive system of Siberian sturgeon during early ontogeny
Authors: Gisbert E. , Sarasquete M. C. , Williot P. , Castelló‐Orvay F.
Published: April 2005

At hatching, the yolk‐sac matrix of Siberian sturgeon Acipenser baeri contained neutral glycoconjugates, glycogen, proteins rich in arginine, lysine, tyrosine, cysteine and cystine, glycoproteins containing mannose (Man) and/or glucose (Glc), N‐acetyl‐D‐galactosamine (GalNAc), L‐fucose (Fuc), sialic acid and/or N‐acetyl‐D‐glucosamine (GlcNAc) residues, as well as neutral and acidic lipids. Buccopharyngeal and anterior oesophageal goblet cellls produced a combination of neutral and acid sialoglycoproteins, while those from the posterior oesophagus secreted only neutral glycoproteins; both types of secretions contained tryptophan and ‐S‐S‐ groups and were unreactive to lectin techniques. Most intestinal goblet cells secreted mainly carboxylated and sulphated sialoglycoproteins with some rests of neutral glycoconjugates, while few of them produced only acid or neutral glycoproteins. Intestinal glycoproteins were rich in GalNAc, GlcNAc and sialic acid residues. Close relationships between digestive enzymes and morphological development of digestive organs were observed. Histochemistry of enzymes revealed that just after hatching, alkaline and acid phosphatase, ATP‐ase and non‐specific esterase activities were detected in the yolk sac. From the onset of exogenous feeding to the juvenile stage (30 days post‐hatch), an enhancement of enzymatic activities was observed, as alkaline and acid phosphatase, ATP‐ase, aminopeptidase M and nonspecific esterase sharply increased. However, lipase activity decreased in the liver and brush border of enterocytes by 13–14 days post‐hatch. Two types of lipase were detected in the alimentary canal, a non‐pancreatic lipase that was secreted in the cardiac stomach by gastric glands, and a pancreatic lipase, which activity was mainly detected in the brush border of the intestinal epithelium.
Analysis of mtDNA indicates weak temporal genetic heterogeneity in pink salmon spawning runs in two rivers on Sakhalin Island
Authors: Brykov Vl. A. , Polyakova N. , Skurikhina L. A. , Kukhlevsky A. D. , Kirillova O. N. , Churikov D. , Pudovkin A. I. , Gharrett A. J.
Published: April 2005

Both odd‐ and even‐year pink salmon populations were sampled during the spawning runs in Firsovka and Bakhura rivers on Sakhalin Island. Four collections of 30 fish spaced at 2‐week intervals were taken from each river in 2 consecutive years. Four restriction endonucleases were used to examine 2·15% of the mitochondrial genome. Eighteen variable sites and three types of insertion defined 37 haplotypes among 449 fish. Heterogeneity tests showed highly significant differences among temporal collections taken in the odd year from Bakhura River, and no significant differences among temporal collections from the other three spawning runs. However, probabilities of homogeneity among temporal collections were low in all tests, and an integral estimate of the probability of homogeneity for the total set of tests was less than 0·001, indicating highly significant overall temporal heterogeneity. Analysis of molecular variance (AMOVA), revealed that a small portion of the variance was distributed among temporal collections, and small φST values that differed significantly from zero only in the odd‐year population in Bakhura River. Temporal differences in spawning are probably adapative, and allow greater productivity in areas of high spawning densities.
Observations on the ecology of a landlocked population of allis shad in Aguieira Reservoir, Portugal
Authors: Collares‐Pereira M. J. , Cowx I. G. , Luís T. Sales , Pedrosa N. , Santos‐Reis M.
Published: April 2005

A landlocked population of the anadromous clupeid Alosa alosa from Aguieira Reservoir in Portugal is described. The individuals are fast‐growing, mature in their third year of life, live for 5+ years, and consequently spawn more than once.
Ascorbic acid and α‐tocopherol levels in larvae of Atlantic halibut before and after exogenous feeding
Authors: Rønnestad I. , Hamre K. , Lie Ø. , Waagbø R.
Published: April 2005

Ascorbic acid (AA) and α‐tocopherol (α‐TOH) levels in whole Atlantic halibut larvae were constant during the yolk sac stage at 170 and 131 ng individual−1, respectively. At hatching c. 80% of the AA and 97% of the α‐TOH were contained within the yolk‐sac compartment. With development, AA and α‐TOH levels in the yolk decreased, at different rates. At first feeding (at 200 day degrees post hatch, D°PH)>95% of AA but <30% of α‐TOH in the yolk at hatching had been transferred to the larval body. Transfer of α‐TOH was completed at 360 D°PH, when the yolk was completely absorbed. The plankton offered to the larvae at first feeding (chiefly Temora longicornis) contained 756 μg g−1 AA and 120 μg g−1α‐TOH (dry weight). The AA content increased to 472 ng individual−1 within one week after first feeding, while it declined slightly in unfed larvae. In fed larvae the AA content reached c. 3500 ng individual−1 at 580 D)PH. The α‐TOH content increased only slightly in the first week of feeding (206 to 431 D°PH), but then increased to > 800 ng individual−1 at 483 D°PH.
Trade‐off between egg mass and egg number in brown trout
Authors: Jonsson N. , Jonsson B.
Published: April 2005

Individual egg mass and fecundity increased with somatic mass in first time and repeat spawning wild anadromous and freshwater resident brown troutSalmo trutta. The egg mass was larger for similar‐sized trout in south (58° N) than mid Norway (63° N), whereas fecundity was higher in mid‐ than in south Norway, making total gonadal investment similar in the two areas. Repeat spawners had heavier eggs than similar‐sized first time spawners. The egg mass of residents wasc.10% larger than that of similar‐sized first time spawning anadromous trout. Common garden experiments with offspring of wild anadromous trout showed no significant correlation between egg and somatic mass in first time spawners in two of the three populations studied. In the third population, a slight positive correlation was found. Similar results were found for repeat spawners. In the three populations, fecundity increased significantly with somatic mass in both first time and repeat spawners. Wild and hatchery‐reared trout showed negative correlation between egg mass and fecundity when the effect of body size was excluded, indicating a trade‐off between the two parameters. In wild trout, this was caused by variation among populations, whereas in hatchery fish, within population variation was observed in egg mass over fecundity. Furthermore, the egg mass of first time and repeat spawners were positively correlated, when adjusted for fish size. Size‐specific gonadal investment was significantly higher in wild anadromous than resident trout. There was no significant difference in gonadal investment between first time and repeat spawners in wild anadromous trout. However, in the hatchery‐reared trout, gonadal investment was significantly higher at repeat than first time maturation. The hatchery trout did not spawn naturally, but were artificially stripped. Among populations, a part of the variation in egg mass and fecundity is phenotypically plastic, a part appears genetically determined.
Spatial and temporal variations in fish populations in the upper Thames estuary
Authors: Araújo F. G. , Bailey R. G. , Williams W. P.
Published: April 2005

Between February 1989 and August 1990, the upper Thames estuary contained 23 species of fish. Fish numbers were higher and relatively constant in the uppermost part of the estuary. Number of species was augmented in summer from fresh water and from downstream, coinciding with high temperature, low flow and high salinity. The eight most abundant species contributed to 98·5% of the total number. Flounder Pleuronectes flesus, dace Leuciscus leuciscus and perch Perca fluviatilis, recruited from May to August, and common goby Pomatoschistus microps, roach Rutilus rutilus and chub Leuciscus cephalus, from August to November. The upper estuary (salinity 0·34–2·96 p.s.u.) formed a species transition area between the freshwater but salinity‐resistant roach, chub, and gudgeon Gobio gobio upstream, and the estuarine eurhyhaline common goby and flounder downstream. The three‐spined stickleback Gasterosteus aculeatus and cyprinids were more abundant at upstream while perch was more abundant at downstream sites. High abundances of gudgeon, chub and roach were associated with high transparency and dissolved oxygen and low salinity, while high abundances of perch were associated with high salinity and low transparency. Dace and three‐spined stickleback were associated with high dissolved oxygen and low pH, and common goby with high pH. Flounder showed no clear preferences.
Feeding rank and dominance in Tilapia rendalli under defensible and indefensible patterns of food distribution
Authors: McCarthy I. D. , Gair D. J. , Houlihan D. F.
Published: April 2005

In four scatter‐fed groups of Tilapia rendalli, the distribution of food between individuals was not significantly different from that expected if the food was shared uniformly between all the fish in the group for nine of the 12 radiographic assessments of feeding behaviour. Individual fish maintained the same feeding rank over time, indicating a stable feeding hierarchy, in only one of the four scatter feeding groups. In contrast, in four point source feeding groups, the distribution of food between individuals differed significantly from uniformity in 10 of the 12 radiographic assessments of feeding behaviour and stable feeding hierarchies were maintained over time in three of the four groups. Thus, scatter feeding promoted a more uniform distribution of food between individuals within the group and prevented the formation of feeding hierarchies. There was no significant correlation between individual feeding rank and dominance index in all four scatter feeding groups. In contrast, significant positive correlations were found between individual feeding rank and dominance index in all four point source feeding groups. The results of this study confirm that feeding rank can be used as a correlate of relative social status under defensible feeding conditions.
Mate guarding in an Amazonian cichlid, Pterophyllum scalare
Authors: Yamamoto M. E. , Chellappa S. , Cacho M. S. R. F. , Huntingford F. A.
Published: April 2005

Aggression by Pterophyllum scalare to an opposite sexed intruder was markedly reduced when the mate was absent. Territorial defence was not vigorous just after the eggs had been released and fertilized. Fish of both sexes attacked intruders of the same sex more intensely than they attacked those of the opposite sex, but males were more aggressive than females in this context. These results suggest that their aggression toward intruders serves to maintain the pair bond.
Effects of alternative prey on cannibalism in age‐1 bluefish
Authors: Bell G. W. , Buckel J. A. , Stoner A. W.
Published: April 2005

Age‐1 bluefish Pomatomus saltatrix were offered both age‐0 bluefish and age‐1 Atlantic silversides Menidia menidia in the following proportions: 0:1·0, 0·25:0·75, 0·5:0·5, 0·75:0·25, 1·0:0. Atlantic silversides were consumed in greater proportion than offered throughout all treatments suggesting strong selection for silversides. There was no evidence of prey‐switching. The behavioural processes leading to age‐1 bluefish selection of Atlantic silversides was investigated. The proportion of attacks on each prey species was distributed randomly, or slightly higher on age‐0 bluefish; however, capture success was greater on silversides than on age‐0 bluefish prey. Therefore, age‐1 bluefish did not actively select for silversides and the observed selection pattern is a result of passive processes. These findings suggest that prey switching between age‐0 bluefish and an alternative prey probably does not act as a stabilizing mechanism in the bluefish population and confirm the importance of capture success in determining piscivore selectivity patterns.
Influence of sex, body size, and reproduction on overwinter lipid depletion in brook trout
Authors: Hutchings J. A. , Pickle A. , McGregor‐Shaw C. R. , Poirier L.
Published: April 2005

Expressed as percentages of total fresh body weight, lipids of brook trout Salvelinus fontinalis declined between October and April: reproductive males from 2·89 to 1·22%, reproductive females from 3·19 to 1·84%, and non‐reproductive males and females from 2·75 to 2·08%. The absolute and proportional overwinter reduction in lipids among reproductive trout was more than twice that of non‐reproductive trout, with reproductive males losing significantly more lipids than reproductive females. Larger reproductive individuals lost more lipids during winter, relative to body size, than smaller individuals, although such an effect was not evident among non‐reproductive trout. The average overwinter reduction in lipids for reproductive males (58%), females (42%), and non‐reproductive trout (24%) was negatively associated with mark‐recapture estimates of overwinter survival probabilities of 0·27, 0·36, and 0·58, respectively, providing support for the hypothesis that energy is allocated to reproduction to the detriment of post‐reproductive survival. Our emergent hypothesis that reproductive costs differ between sexes, and the life history consequences thereof, merit further study.
Intracellular ion levels in erythrocytes and hepatocytes isolated from three teleost species
Authors: Furimsky M. , Perry S. F. , Moon T. M.
Published: April 2005

Intracellular concentrations of Na+ and K+ were similar (∼75 mmol l−1) in rainbow trout Oncorhynchus mykiss hepatocytes directly following isolation by collagenase digestion, but partial recovery occurred over 6 h with K+ levels increasing to 110 mmol l−1 and Na+ levels decreasing to 42 mmol l−1. Black bullhead Ameiurus melas hepatocytes exhibited higher intracellular concentrations of K+ (90 mmol l−1) than Na+ (55 mmol l−1) with no recovery occurring over 6 h following cell isolation. Concentrations of Na+, K+ and Cl− in eel Anguilla rostrata hepatocytes were similar (∼ 55 mmol l−1) following isolation, with no recovery occurring over time. Erythrocytes from all species apparently did not experience an intracellular ion imbalance following isolation as indicated by high K+ levels (<140 mmol l−1) and low Na+ levels (<40 mmol l−1) during the entire 24‐h monitoring period. Although hepatocytes from all species exhibited an ion imbalance post‐isolation, comparison of their in vitro intracellular Na+ and K+ concentrations with those in plasma demonstrated that directionally correct ion gradients still exist across the cell membrane, albeit differing from those that would be found in the tissue in vivo.
A tool to facilitate implantation of electrodes for electromyographic telemetry experiments
Authors: Bunt C. M.
Published: April 2005

Conventional techniques for implanting electrodes into axial swimming musculature of fish are reviewed. A new device is described that reduces time for electrode implantation, ensures constancy in electrode orientation, implantation depth, and separation distance. This device is inexpensive, simple to build, and easy to use.
The effects of predator size, temperature, and prey characteristics on gastric evacuation in whiting
Authors: Andersen N. G.
Published: April 2005

No effect of prey size on gastric evacuation rate was found in whiting Merlangius merlangus.Prey energy density explained most of the data variation among fish prey, and evacuation time increased by a factor 1·6–1·7 with prey energy density increasing from 3·4 to 5·6 kJ g−1. The power model expanded to include predator size, temperature, and prey energy density could describe gastric evacuation in whiting fed fish prey. Krill Meganyctiphanes norvegica was evacuated at a rate similar to fish prey of equal energy density, while the evacuation of brown shrimp Crangon crangon took almost twice as long.
Use of the lateral line for feeding in two Lake Baikal sculpins
Authors: Janssen J. , Sideleva V. , Biga H.
Published: April 2005

Batrachocottus baicalensis, endemic to Lake Baikal, Russia, has wider lateral line canals than Paracottus kneri, which also inhabits Siberian streams. In quiet water B. baicalensis responded to amphipods at a greater distance than did P. kneri. Batrachocottus baicalensis also moves less often from search positions than does P. kneri. Fish responded to faster moving prey at a greater distance than slower prey. They also responded to a greater distance to prey moving more parallel to the fish's body surface. In an artificial stream B. baicalensis responded only to prey that touched them whilst P. kneri responded to both swimming prey and prey that contacted them. It is argued that B. baicalensis is primarily an ambush predator that is a habitat specialist and P. kneri is a cruising predator that visits many habitats.
Reassessment of the generic position of the Iberian cyprinid alburnoides complex: its return to the genus Leuciscus
Authors: Collares‐Pereira M. J. , Alves M. J. , Coelho M. M.
Published: April 2005

The generic position of the Iberian unisexual fish complex alburnoides is reassessed based on genetic evidence of a hybrid ancestry and of a monophyletic relationship with endemic Leuciscus taxa. There is a continuous movement of genes between the different forms of the complex and the main mode of reproduction is by meiotic hybridogenesis. Thus its return to the original generic position Leuciscus is recommended. © 1999 The Fisheries Society of the British Isles
Genetic and morphological variation between two forms of lacustrine brook charr
Authors: Dynes J. , Magnan P. , Bernatchez L. , Rodríguez M. A.
Published: April 2005

Genetic data suggest that the littoral and pelagic forms of brook charr Salvelinus fontinalis in Lake Bondi are two populations with partial reproductive isolation and non‐random mating. Genetic differentiation between the two groups was supported by differences in allele frequencies and by deviation from Hardy‐Weinberg equilibrium when the two groups were pooled; no such deviation was observed when fish were divided into littoral and pelagic groups. In contrast to Lake Bondi, no clear evidence of genetic differentiation was observed in Lake Ledoux. Discriminant function analyses of morphological characters support the existence of littoral and pelagic groups in Bondi and Ledoux Lakes. In Lake Bondi, the two groups differed significantly in two shape variables (pelagic fish had shorter dorsal fins, and longer body length posterior to the dorsal fin than littoral ones) whereas in Lake Ledoux, the groups differed in four shape variables (pelagic fish had shorter pectoral fins, shorter dorsal fins, and a shorter and higher caudal peduncle than littoral ones). Discriminant analyses of these characters were effective in reclassifying fish into their appropriate groups in both populations, with an efficiency of 78% for juveniles in Lake Bondi and 69% for adults in Lake Ledoux. Differences in morphology between the two forms are consistent with adaptations required to forage in each zone, i.e. benthic form in the littoral zone and planktivorous form in the pelagic zone.
Interannual and regional variations in body length, weight and energy content of age‐0 Pacific herring from Prince William Sound, Alaska
Authors: Paul A. J. , Paul J. M.
Published: April 2005

Age‐0 Pacific herring were surveyed in October of 4 years in a large northern Gulf of Alaska estuary, to determine the range of variations in length, weight and whole body energy content (WBEC). These parameters reflect their preparedness for surviving their first winter's fast. During the surveys there were distinct regional and interannual variations in all three parameters for individual groups of herring in Prince William Sound. Likewise, with each collection there was typically a large range of size and WBEC values. The average standard length was (±S.D.) 80±13 mm (range=40–118), the mean whole body wet weight was 5·7±3·0 g (range=0·7–29·2) and the average WBEC of all age‐0 herring captured, regardless of year or site (n=1471), was 5·4± 1·0 kJ g−1 wet weight (range=2·4–9·4). The large range of WBEC and size indicates that age‐0 herring at different capture sites were not all equally prepared for surviving their first winter.
Correlates of the duration of the egg collecting phase in the three‐spined stickleback
Authors: Kraak S. B. M. , Bakker T. C. M. , Mundwiler B.
Published: April 2005

Individual male three‐spined sticklebacks in the field, often collected eggs for longer (up to 10 days) than had been reported for sticklebacks in captivity (3–6 days). The probability that a male stopped collecting eggs increased with the number of eggs already present, and possibly with the age of the eggs. Males with nests hidden under a plant were more likely to continue collecting than males with exposed nests. These results are discussed in the light of theoretical considerations that predict when males should stop collecting further eggs.
Seasonal leukocyte and erythrocyte counts in fathead minnows
Authors: Thomas M. B. , Thomas W. , Hornstein T. M. , Hedman S. C.
Published: April 2005

Leukocyte and erythrocyte counts on normal fathead minnows Pimephales promelas showed a marked seasonal trend. In a period from June to March, a three‐fold increase in leukocytes was seen during August and September.
The effects of temperature and size on growth and mortality of cod larvae
Authors: Steinarsson A. , Björnsson B.
Published: April 2005

The optimal temperatures for growth of four groups of hatchery‐reared cod larvae (geometric mean weight: 73, 191, 249 and 251 μg), reared on rotifers at four or five constant temperatures between 4 and 16° C for 14, 12, 9 and 16 days were 9.7, 12.3, 12.7 and 13.4° C, respectively. The maximum growth rate also increased with size and was 6.5, 9.6, 11.7 and 11.3% day−1 for the respective size groups. The optimal temperature for survival was 8.5–8.8° C for all size groups. The results indicate an opposite relationship between (1) size and optimal temperature for growth and (2) size and maximum growth rate of cod larvae, to that observed for juvenile and immature cod.
The influence of different parental combinations and incubation temperature on the RNA and DNA content of herring larvae at hatching: a pilot study
Authors: Høie H. , Folkvord A. , Johannessen A.
Published: April 2005

In four half‐sib pairings, herring mothers affected the standard length, dry weight, and RNA and DNA content of their progeny, while fathers affected larval RNA and DNA content. The amounts of RNA and DNA in offspring from one male were also influenced by temperature in that the highest RNA contents were found at the lowest temperature and highest DNA contents at the highest temperature. The results indicate that both environmental and genetic factors influence nucleic acid contents of young herring larvae, and this may limit the suitability of RNA : DNA ratio as a condition measure of newly hatched herring larvae.
Resistance of perch eggs to attack by aquatic fungi
Authors: Paxton C. G. M. , Willoughby L. G.
Published: April 2005

In the distinctive gelatinous Perca fluviatilis egg mass, limited fungal growth by Aphanomyces and Saprolegnia spp. especially S. diclina, occurred within dead eggs but did not spread to adjacent live eggs. Perch eggs exposed to parasitic challenge by Saprolegnia parasitica, S. dieclina (type III) and S. ferax, under fluctuating temperature regimes replicating spring water temperatures, did not have significantly greater mortality than did unchallenged controls. The observations suggest that perch eggs have some anti‐fungal properties which usually prevent the spread of fungus throughout the egg mass and that under normal spring temperatures there should be negligible ecological consequences of fungal infection in perch egg masses.
Mitochondrial DNA diversity in North American and European Atlantic salmon with emphasis on the Downeast rivers of Maine
Authors: King T. L. , Spidle A. P. , Eackles M. S. , Lubinski B. A. , Schill W. B.
Published: April 2005

The displacement loop and NADH‐1 dehydrogenase regions of mitochondrial DNA (mtDNA) were amplified by the polymerase chain reaction in 954 Atlantic salmon and digested with 40 restriction endonucleases. Variation was detected with 10 enzymes, resulting in 21 composite haplotypes which were strongly patterned geographically with a major discontinuity observed between most North American (NA) and European salmon. Significant heterogeneity of haplotype frequencies was found within and among all classification levels (continent, country, and river). Haplotype frequencies were significantly different across continents, within European samples, within NA samples, within Canadian samples, within wild Maine samples, within captive Maine strains, and between captive and wild Maine strains. Nine haplotypes occurred only in NA, seven in Maine, three only in Maine, and 11 occurred only in Europe. Some Maine rivers had only a single haplotype, suggesting that effective population sizes may be low. The second most frequent European haplotype occurred in tributaries to one Newfoundland river. Gene trees based on parsimony and genetic distance suggest that the haplotypes are monophyletic within each continent, and that the haplotype found on both continents is intermediate between those of Europe and NA, suggesting common ancestry of all haplotypes.
Female mate choice and spawning behaviour of Chinook salmon under experimental conditions
Authors: Berejikian B. A. , Tezak E. P. , LaRae A. L.
Published: April 2005

After spawning their first nest, female chinock salmon Oncorhynchus tshawytscha paired with small males (c. 46% of female weight) spent an average of 16·2 h between spawning of successive nests compared with 9·6 h for females paired with large males (c. 112% of female weight) (P< 0·05). Neither frequencies of female nest construction behaviours (digging and probing) nor male courtship behaviour (crossovers and quivers) differed between large‐ and small‐male pairs. Male quivering frequencies were correlated significantly with female digging and probing frequencies, whereas the crossover frequencies were not. It is suggested that delayed spawning by females in the presence of relatively small males is a primary mechanism by which females in the genus Oncorhynchus exhibit mate choice.
Biology and ecology of Nezumia liolepis and N. stelgidolepis from the west coast of North America
Authors: Hoff G. R. , Buckley T. W. , Drazen J. C. , Duncan K. M.
Published: April 2005

Nezumia liolepis and Nezumia stelgidolepis were collected during a National Marine Fisheries Service 1997 groundfish survey along the Pacific coast of North America. Bottom trawling was conducted from 188 to 1260 m depths. Nezumia liolepis were collected from 581 to 1247 m (3·4–5·7°C) and N. stelgidolepis from 285 to 555 m (6·0–8·4°C). The two species had distinct depth and temperature distributions and the majority of the specimens for each species came from narrow depth ranges. Nezumia stelgidolepis attains a larger pre‐anal fin length (117 mm) than N. liolepis (83 mm), and age estimates from otolith ring counts indicate ages from 3 to 9 years for N. liolepis and 7 and 13 years for N. stelgidolepis from specimens collected. The gonads of N. liolepis were not reproductively active, and a single N. stelgidolepis possessed eggs of various sizes suggesting batch spawning. N. liolepis and N. stelgidolepis fed benthically, primarily on crustaceans such as amphipods, shrimp, mysids and polychaete worms. Although diet overlap was high, these two species appear to limit competition for resources by habitat separation.
Influence of different rations and water temperatures on the growth rates of shortfinned eels and longfinned eels
Authors: Graynoth E. , Taylor M. J.
Published: April 2005

Juvenile (12–152 g) shortfinned eelsAnguilla australisand longfinned eelsA. dieffenbachiacaught in New Zealand streams were fed squid mantleNototodarusspp. 4 days per week in laboratory experiments. A linear multiple regression equation showed the amount of food eaten (0–2·7% w day−1) explained 77·7% of the variation in specific growth rates (–0·60 to +1·07% w day−1) among individual eels, while previous growth rates, water temperature (10·0–20·6°C), and eel weight (12–152 g) explained a further 5·6, 1·4 and 0·8%, respectively. Growth in length ranged from –0·3 to +0·9 mm day−1. Eels which were starved and then given high rations grew substantially faster than expected. Once growth rates were adjusted for differences in ration and other factors, there were no significant differences in growth rates between species or individual fish. Growth of shortfinned eels fed maximum rations of commercial eel food depended on fish size and water temperatures and ceased below 9·0°C. Growth rates in the wild were substantially less than the maximum possible, after seasonal changes in water temperatures were taken into account, indicating that food supplies and not low water temperatures were controlling growth rates in the wild.
Salt stress and resistance to hypoxic challenges in the common carp (Cyprinus carpio L.)
Authors: De Boeck G. , Vlaeminck A. , Van der Linden A. , Blust R.
Published: April 2005

Long term exposure to brackish water (171 mm NaCl) affected the capacity of common carp Cyprinus carpio to deal with hypoxic conditions and the critical oxygen concentrations for oxygen consumption increased. In addition, regulation of ammonia excretion was lost. The cytosolic phosphorylation potential (the index of the energy status of a cell in terms of potential transferable phosphate groups) in the lateral muscle on the other hand remained relatively unaffected, indicating that oxygen transport to the tissues was not severely compromised. It appears that exposure to brackish water reduces the capacity of common carp to cope with hypoxic conditions mainly because of the high energetic cost of hyperventilation under conditions where energy stores are depleted, and not because of any impeded oxygen transport mechanisms.
Carotenoid‐based sexual coloration and body condition in nesting male sticklebacks
Authors: Barber I. , Arnott S. A. , Braithwaite V. A. , Andrew J. , Mullen W. , Huntingford F. A.
Published: April 2005

The extent, corrected for body size, and intensity of nuptial coloration of breeding male three‐spined sticklebacksGasterosteus aculeatusL. from a Scottish freshwater population were highly variable but correlated, both in the field and after a period of nest‐building in the laboratory. However, marked changes in coloration occurred between the field and the laboratory screenings and the coefficients of variation amongst males decreased. In general, intensity of coloration increased between the field and laboratory screenings, but changes in size‐corrected extent were not consistently directional. For both indices, there was a negative relationship between the field value and amount by which colour changed between sampling sessions, with fish that were initially the dullest gaining most in colour. Size‐corrected extent and (in particular) intensity of coloration in the field sample were associated positively with body condition measured post mortem and there was a negative, though non‐significant, relationship between the extent of coloration and the proportion of white cells in the blood. No such associations were found for the laboratory colour screening. The concentration of astaxanthin in the lower jaw was related strongly and positively to both size‐corrected extent and intensity of coloration at the laboratory screening and related negatively, though non‐significantly, to proportional white cell counts. These data have implications both for the interpretation of previous laboratory studies and for the design of future experiments, and suggest that coloration is only a true indicator of male quality when measured in the field.
Diet, growth and competitive abilities of sympatric whitefish forms in a dense introduced population: results of a stocking experiment
Authors: Heikineheimo O. , Miinalainen M. , Peltonen H.
Published: April 2005

The food of five whitefish stocks Coregonus lavaretus planted in Lake Vuokalanjärvi consisted mainly of zooplankton and insects taken from the water surface. The amount of benthic food in the diet of the two sparsely gill‐rakered (23 and 28 rakers) stocks increased from the age of 2 years onwards. The growth of whitefish was slow in all stocks. The densely gill‐rakered stock (50–51 rakers) originating from the same lake system as Lake Vuokalanjärvi grew faster than the other stocks, and the food consumption of 4‐ and 5‐year‐old fish belonging to this stock was nearly double compared with the other stocks. The habitat choice of the whitefish differed between the stocks even in the densely‐rakered stocks classified as the same form. A stock with flexible habitat use and feeding habits is most likely to succeed. Introducing whitefish stocks from distant areas is not advisable.
High genetic diversity, large inter‐oceanic divergence and historical demography of the striped mullet
Authors: Rocha‐Olivares A. , Garber N. M. , Stuck K. C.
Published: April 2005

The striped mullet Mugil cephalus, L. is a circumtropical species whose extreme conservative morphology stands in contrast with the degree of genetic differentiation at a global scale. One hundred and fourteen mitochondrial control region DNA sequences were analysed from four localities in the Gulf of Mexico (Texas, Louisiana, Mississippi, Florida), one on the U.S.A. east coast (N. Carolina), and one in Hawaii, giving very high levels of molecular diversity (h=1·0 every haplotype was unique in all samples, π=1·1–2·0% in Gulf–Atlantic and π=3·1% in Hawaii). With no genetic evidence of dramatic population expansions, mismatch distributions were still very different in each ocean. Stable population levels in Hawaii have fostered the generation and persistence of very high molecular diversity, but Gulf–Atlantic samples suggest a shorter span of population stability. Ninety‐five per cent of the molecular variance was allocated between ocean basins and virtually none among Gulf–Atlantic samples. A neighbourjoining reconstruction revealed Atlantic‐ and Pacific‐specific lineages separated by more than 24% uncorrected sequence divergence (d=0·49 Tamura‐Nei Gamma‐corrected). The lack of phylogeographic structure among Gulf–Atlantic samples corroborated the AMOVA results and supported the existence of a single population with high levels of gene flow along the Gulf of Mexico and north‐west Atlantic coasts. The genetic differentiation between oceans points to the absence of gene flow and an accelerated rate of mitochondrial evolution in the genus Mugil.
Vertical distribution and feeding of larval blue whiting in turbulent waters above Porcupine Bank
Authors: Hillgruber N. , Kloppmann M.
Published: April 2005

In April 1995 a patch of blue whiting larvae Micromesistius poutassou was found at low illumination levels below 20 m depth near Porcupine Bank, west of Ireland, together with high densities of copepod nauplii and reduced turbulence rates, suggesting that larval blue whiting vertical distribution was determined by prey concentration, illumination and turbulence. Most (83·8%) larvae (2·0–7·5 mm Ls) had food in their guts. Feeding incidence and feeding intensities increased with increasing larval length. Only larvae >5·5 mm reduced numerical in favour of weight‐based feeding intensity, indicating a shift in dietary composition. Maxima of the diel rhythms of feeding incidence and intensities occurred at 1800 and 2100 hours and minima at dawn (0600 hours). Proportionately, more nauplii were eaten by day but more copepod eggs and tintinnids at night. The distinct diel pattern in larval blue whiting feeding suggests that any analysis of factors mediating feeding must take into account diel feeding cycles. Larval feeding was significantly affected by wind speed. The larvae ate more and larger items at low than at higher turbulence levels. The data suggest that the maximum level of turbulence was not beneficial for larval blue whiting, but more moderate wind speeds could have had an enhancing effect on larval feeding success.
DNA sex identification in the three‐spined stickleback
Authors: Griffiths R. , Orr K. L. , Adam A. , Barber I.
Published: April 2005

Two sex linked DNA markers are isolated in the three‐spined sticklebackGasterosteus aculeatusand a sex identification test is developed.
Fertilization in landlocked sea lamprey: storage of gametes, optimal sperm: egg ratio, and methods of assessing fertilization success
Authors: Ciereszko A. , Glogowski J. , Dabrowski K.
Published: April 2005

Ovulated, unfertilized eggs of sea lamprey Petromyzon marinus could be stored for 1 day at 15° C without significant loss of fertilizing ability. After 2 days storage most eggs could still be fertilized. Lamprey semen could be stored up to 1 day. Thereafter, a decrease in sperm fertilizing ability occurred, accompanied with a decrease in sperm motility. Unlike teleost fish, sea lamprey eggs could still be fertilized after 1 h contact with water. This extended time of gamete fertility after release into water may help to account for the reproductive success of this species. Maximal fertilization rates were obtained at a sperm: egg ratio of 50 000, a ratio recommended for studies on fertility of individual males. Assessing fertilization success 3 min after fertilization (at cytoplasmic bleb stage) or 5 h after fertilization (at two–cell embryo) was strongly correlated (r=0·92 and 0·98) with estimation and fertilization success at hatching. These results offer improvement in artificial fertilization techniques under laboratory conditions and provide new information on the biology of fertilization in sea lamprey.
A long‐term view of density‐dependent recruitment in smallmouth bass from Nebish Lake, Wisconsin
Authors: Gillooly J. F. , O'keefe T. C. , Newman S. P. , Baylis J. R.
Published: April 2005

In a closed population of smallmouth bass Micropterus dolomieui during a 9‐year period in Nebish Lake, Wisconsin, total egg production in spring, the percentage of constructed nests that receive eggs, and the mean number of eggs/nest were inversely related to spawning stock biomass. Yet, there was no relationship between total egg production or spawning stock biomass and total young‐of‐the‐year production in autumn of the same year. Together, these results suggest that density‐dependent processes regulate egg production, but not young‐of‐the year production, in smallmouth bass.