bluuebunny/crossref_metadata_2025 huggingface dataset:
The impact of the introduction of Nile perch, Lates niloticus (L.) on the fisheries of Lake Victoria
Authors: Achieng A. P.
Published: January 2006

The piscivorous Nile perch was introduced into Lake Victoria some 30 years ago, since when it has completely transformed the fishing industry and the species composition of the fish fauna of the lake. The original multispecies fishery, based mostly on cichlids (haplochromines, tilapias), cyprinids (Barbus, Labeo, Rastrineobola) and siluroids (Bagrus, Clarias, Synodontis, Schilbe), has changed dramatically to one based on three species: the introduced Nile perch, the cyprinids, Rastrineobola argenrea (Pellegrin), and the introduced Nile tilapia, Oreochromis niloticus (Linnaeus).

Within 25 years of its introduction the Nile perch became ubiquitous and now occurs in virtually every habitat with the exception of swamps and affluent rivers. It has preyed on all other species with profound effects, especially on the stocks of haplochromines. These originally comprised 80% of the total fish biomass in Lake Victoria, but have now decreased to less than 1% offish catches from the Kenyan waters of the lake. The fishermen of Lake Victoria have adjusted to this ecological crisis by using large‐meshed nets to catch Nile perch, which has become the most important commercial species. For the first time in the history of Lake Victoria, fish fillets are now being exported to several overseas countries: the fillets are all from Nile perch.
Introductions of distinct stocks of chum salmon, Oncorhynchus keta (Walbaum), into natural populations of the species
Authors: Altukhov Yu. P. , Salmenkova E. A.
Published: January 2006

Populations of chum salmon, Oncorhynchus keta, are recognizable by the allelic frequencies of allozyme loci. Identification of these was used to assess the return of spawning adults to alien rivers into which they were introduced via hatchery‐reared, artificially‐fertilized eggs obtained from populations elsewhere in the Soviet Far East. Coefficients of return to spawn in the alien rivers were much lower than returns for the native fish, and in succeeding generations the alien fish disappeared from the spawning runs. It is concluded that transplanting salmonid eggs between populations is ineffective as a means of establishing new stock in territory already occupied by another stock, and the practice is deplored on grounds of conserving unique gene pools within species.
Genetic approaches to conservation of rare fishes: examples from North American desert species
Authors: Meffe G. K.
Published: January 2006

Long‐term prospects for conservation of rare fishes depends, in part, on the availability of genetic variation within populations as the raw material to respond to natural selection and allow continued evolutionary change. It is thus important to obtain information on the extent and distribution of genetic variation in rare fishes. There are at least six applications of such genetic data in recovery efforts: description of the quantity and distribution of genetic variation in a species; estimation of historical levels of isolation and gene flow; identification of unique gene pools for special protection; contributions to taxonomic clarifications; information for choosing brood stocks; and monitoring of hatchery populations. It is only through such informed management and with an evolutionary perspective that we can maximize probabilities for conservation in perpetuity of rare fishes.
Captive breeding for the conservation of cichlid fishes
Authors: Reid G. McGregor
Published: January 2006

Cichlid fishes are by far the largest familial group of endangered vertebrates, especially the haplochromines. This paper concerns the organization and management of captive breeding of haplochromine cichlids. The setting up of a small‐scale laboratory programme for the conservation of endangered species is described in terms of funding, staffing, installation and livestock husbandry. Breeding is discussed in the context of the selection of broodstock, basic reproductive biology, rearing, disease, pathological disorders and the arrangements necessary for the transfer and documentation of progeny. There are already indications in Africa and elsewhere that the dramatic decline and demise of cichlid taxa in Lake Victoria will not be an isolated phenomenon. There is no prospect that the captive breeding of cichlids can alone resolve such large‐scale problems in fisheries management and ecology, or prevent the loss of taxa in nature. Nevertheless, captive breeding provides conservation options which are otherwise limited or unavailable regarding the saving of individual ‘heritage’ species, restocking to the wild, fundamental laboratory research and, finally, public education on the grave issue of actual and prospective mass extinctions of cichlids and other rare fishes.
Attraction of zebrafish, Brachydanio rerio, to alanine and its suppression by copper
Authors: Steele C. W. , Owens D. W. , Scarfe A. D.
Published: January 2006

Preference responses of zebrafish to 10−3, 10−4 and 10−5M alanine (Ala) were concentration‐ dependent. Behavioural responses to copper (Cu) and Cu + Ala mixtures were also assessed. Zebrafish avoided 100 and 10 μg Cu l−1, but not 1 μg l−1. Mixtures of 10−3 m Ala+ 100 μg Cu l−1 and 10 4 M Ala + 10 μg Cu 1−1 were avoided as intensely as was Cu alone. Responses to 10−3 M Ala + 10 or 1 μg Cu l−1 and 10 4 M Ala +1 μg Cu l−1 did not differ statistically from controls (no detectable preference or avoidance). These results demonstrate, firstly, that a concentration of a pollutant avoided by itself (10 μg Cu l−1) may not be avoided when encountered with an attractant chemical stimulus (Ala) and may suppress the preference for an attractant stimulus, and secondly, that a concentration of a pollutant not avoided by itself and not considered deleterious (1 μg Cu l−1) suppresses attraction to Ala (an important constituent of prey odours for many fishes).
Recognition of cohorts and growth of larval and juvenile roach Rutilus rutilus (L.), using size‐class ordination of developmental steps
Authors: Copp G. H.
Published: January 2006

Roach larvae and 0+ juveniles were sampled weekly in three different floodplain channels (stagnant, semi‐lotic, lotic) of the Upper Rhône River, France, from spring to autumn 1985 using Point Abundance Sampling by electrofishing. Length‐frequency analysis by size‐class ordination of developmental steps successfully distinguished both overlapping and non‐overlapping histograms within the data matrix and revealed the temporal and spatial segregation of a number of cohorts, individuals born at a common site on the same day, which in some cases presented significant differences in standard length within a given developmental step. Despite these initial differences, the various cohorts converged to form one relatively homogeneous cohort around the moment of transition to the juvenile period. Significant differences in standard length were found between populations in the open lotic channel (relatively cooler) and those in the closed, stagnant (relatively warmer) former channel, suggesting that fish growth in isolated ecosystems is influenced by higher or periodically elevated temperatures and by greater levels of resource competition and predation. A similar pattern of differences in length was also observed in 0+ juvenile roach collected from 18 other floodplain channels of the Upper Rhône.
Back‐calculation of fish length: a critical review
Authors: Francis R. I. C. C.
Published: January 2006

A review is made of the literature on the back‐calculation of fish body length from marks on scales or other hard parts (otoliths, vertebrae, fin rays, etc.). Though the technique is widely used it does not appear to be well understood. Regression methods are commonly used, apparently in ignorance of the more realistic proportional methods. It is not generally recognized that there are two equally plausible back‐calculation hypotheses which can lead to significantly different back‐calculated lengths. The Fraser‐Lee equation, the most commonly used back‐calculated formula, follows neither of these hypotheses but is based on a misuse of linear regression. It is recommended that back‐calculation be restricted to procedures following one of the proportional hypotheses; that the difference between lengths calculated using the two hypotheses is a useful measure of the minimum uncertainty in back‐calculation lengths; and that more attention be paid to validating back‐calculation hypotheses by comparing observed and back‐calculated lengths for individual fish. The pattern of heteroscedasticity in body length–scale radius plots is noted as a useful diagnostic in evaluating back‐calculation hypothesis.
Genetic basis of life‐history variation of dwarf and normal Arctic charr, Salvelinus alpinus (L.), in Stora Rösjön, central Sweden*
Authors: Svedäng H.
Published: January 2006

The genetic basis of life‐history variation of dwarf and normal Arctic charr forms in Stora Rosjon was studied by means of two separate rearing experiments on the progeny of artificially bred wild fish. The concept of differential life‐strategies gained support, since the progeny of the normal charr form had a higher growth rate and became sexually mature at a larger size and later age than the progeny of the dwarf charr form. The hybrid progeny (dwarf × normal parental charr) was recognized as intermediate in growth as well as in size and age at maturity, compared to the normal and dwarf progeny. However, a dominance effect of the growth and maturation pattern of the dwarf charr was revealed, since hybrid progeny were more similar to dwarf than to normal progeny. The rearing experiments also support the view that the dwarf and normal charr forms are inherited characteristics of one population, since any individual progeny cannot be assigned to a certain form according to its size and age at maturity.
Effects of temperature on the food processing of three species of seaweed‐eating fishes from European coastal waters
Authors: Horn M. H. , Gibson R. N.
Published: January 2006

Food consumption, gut transit times and assimilation efficiencies of the temperate fishes Lipophrys pholis and Parablennius sanguinolentus (Blenniidae) and Gobius cobitis (Gobiidae. when fed the green alga Ulva lactuca were determined at four temperatures in the laboratory. Food consumption increased and gut transit times decreased with increase in temperature in all three species. Assimilation efficiencies for algal carbon and nitrogen did not vary with temperature in G. cobitis. Carbon but not nitrogen assimilation efficiency varied with temperature in P. sanguinolentus, and both carbon and nitrogen assimilation efficiencies changed broadly with temperature in L. pholis, the most omnivorous of the three fishes. Assimilation efficiencies of all three species were generally within the previously reported ranges for herbivorous marine fishes. These species are thus clearly capable of extracting energy from algal food sources.
Ophidian lozanoi (Pisces: Ophidiiformes) an undescribed ophidiid from the North East Atlantic
Authors: Matallanas J.
Published: January 2006

Ophidion lozanoi n.sp. is characterized by four rakers in the lower limb of the first gill arch; a large rostra1 spine; 24–26 pectoral rays; four rows of palatine teeth, and body squamation beginning at the occiput.
The effect of humic substances on the toxicity of aluminium to adult rainbow trout, Oncorhynchus mykiss (Walbaum)
Authors: Witters H. E. , Van Puymbroeck S. , Vangenechten J. H. D. , Vanderborght O. L. J.
Published: January 2006

Some physiological parameters were measured in adult rainbow trout during a 10‐day exposure to 180 μg Altotal l−1 in acid water (pH 4.7) with or without humic substances (10 mg l−). The fish were acclimatized to pH 5.0 for 7 days prior to the experimental treatments.

Chemical analyses revealed that, in the presence of human substances, 74–80% of the A1 was organic bound, while in the absence of humic substances most of the Al(987percnt;) occurred in the inorganic form.

Al bound to humic substances (13–150 μg l−1) did not alter the plasma NaCl‐concentration, nor the haematocrit value, of rainbow trout during an exposure period of 10 days. This contrasts with the high death rate obtained within 2–3 days when most of the A1 (175 μg l−1) was in the inorganic form. The lethality was accompanied by a 25% decrease in the plasmaconcentration of NaCl and a doubling of the haematocrit value. Bulk analysis revealed that when the metal was present in inorganic forms the total Al content of the gills (75 μg A1 g−1 wet weight) was 15 times higher than when it was present as bound to the humic substances. These experiments showed that the accumulation of A1 at the gills was accompanied by physiological disturbances, both being a function of the chemical speciation of Al.
Changes in the prey ingested and the variations in the Nile perch and other fish stocks of Lake Kyoga and the northern waters of Lake Victoria (Uganda)
Authors: Ogutu‐Ohwayo R.
Published: January 2006

The fish stocks of Lakes Kyoga and Victoria have changed since Nile perch, Lates niloticus (L.), was introduced, and this is reflected in the prey ingested by the predator. Initially, haplochromine cichlids constituted the main prey of most sizes of Nile perch. As the stocks of these have declined, Caridina nilotica (Roux) and Anisopteran nymphs have become the dominant food of the juveniles, while Rastrineobola argentea (Pellegrin), juvenile Nile perch and Oreochromis niloticus (L.) have become the main food of larger Nile perch. Apart from R. argentea, most of the native fish species of these lakes have disappeared. The stocks of Nile perch in Lake Kyoga, to which it was introduced earlier than to Lake Victoria, have declined after dominating the fishery since 1965. and have been superseded by O. niloricus. an introduced herbivore. Similar changes are now occurring in Lake Victoria. The Nile perch might not maintain the high yield realized in the two lakes when haplochromines were abundant. It is therefore necessary to exercise caution with high and long‐term investments aimed specifically at developing the Nile perch fishery.
Hexaploidy in yellowfish species (Barbus, Pisces, Cyprinidae) from southern Africa
Authors: Oellermann L. K. , Skelton P. H.
Published: January 2006

Five small‐scaled yellow fish (large Burbus spp.) from southern Africa are shown to have modal 148 or 150 chromosomes. Themajority ofcyprinid species have 2N = 50 chromosomes, indicating that the yellow fish karyotype is hexaploid in origin. However, as there is no indication that the species are unisexual or that normal reproduction occurs by any means other than bisexual fertilization, the yellowfish karyotype is considered to have reverted to a diploid condition.
American plaice, Hippoglossoides platessoides (Fabricius), predation on green sea urchins, Strongylocentrotus droebachiensis (O. F. Muller), in eastern Newfoundland
Authors: Keats D. W.
Published: January 2006

Green sea urchins were the most abundant food species (62% by weight) in American plaice (all female) collected from an area in eastern Newfoundland where sandy bottom abuts urchin dominated bedrock. Of secondary importance were capelin (12.9% by weight), which were spawning in the area when the samples were obtained. The results suggest that American plaice may be important predators of urchins in such habitats.
Evidence of a genetic component in the seasonal return pattern of Atlantic salmon, Salmo salar L.
Authors: Hansen L. P. , Jonsson B.
Published: January 2006

We tested the null hypothesis that differences in the seasonal return patterns between stocks of Atlantic salmon, Salmo salar L., are a result of a direct response to the environment, and not under genetic control. Two stocks were used in the experiments, originating from the R. Figga and R. Imsa, respectively. In their native habitat fish from the former are known to return to the home stream as adult salmon early in the summer, while from the latter return during late summer and autumn. By rearing these stocks in the same hatchery and releasing smolts of both stocks together at three sites in southern Norway, it was demonstrated that salmon from the R. Figga stock returned earlier to coastal Norway than salmon from the R. Imsa stock, as maturing adults. Thus, we reject the hypothesis that these stocks are genetically identical in this trait. Within both stocks, multi‐sea‐winter fish returned earlier than one‐sea‐winter fish. Within stocks, there was no significant difference in time of return between salmon released as 1‐ and 2‐year‐old smolts, or between fish reared from parents ascending the R. Imsa early or late in the season.
Effect of habitat types on survival, spatial distribution and production of an allopatric cohort of Atlantic salmon, Salmo salar L., under conditions of low competition
Authors: Heggenes J. , Borgstrøm R.
Published: January 2006

An allopatric cohort of Atlantic salmon, Salmo salar L., introduced to a small previously fishless stream was studied from parr to the smolt stages. In May 3900 0+ parr (mean total length 30mm) were planted at three different densities in habitats with slow, intermediate and fast water velocities. During the first year, high mortality occurred during the first 7 weeks after planting in May, and in September–October. Survival from May 1985 to April 1986, before the smolt emigration, was24.8%. The smolt yield 1 year after planting was 15.5%. It is suggested that the high survival was caused by low competition. Most of the redistribution of the fish took place during the first months. Type of planting habitat affected the timing of redistribution. The parr left slow‐flowing, deep habitats with fine substrate soon after planting, while redistribution was slowest in the fastest flowing habitats with coarse substrate. The observed avoidance of slow, deep habitat types in the absence of interspecific competition, suggests that this may be a fixed behavioural response, and not due to competition. Long movements, up to 800 m, were recorded only within the first 7 weeks after planting. The effect of planting densities on population density was most pronounced immediately after planting in the fast and also intermediate habitats. Planting density effects declined and were not detectable after 1 year. The effect of habitat type on fish numbers and biomass was pronounced irrespective of planting densities. Growth was fastest in the intermediate habitat, and at the lower planting densities. Production was 7.2 g m−2 the first summer‐autumn. Due to smolt emigration, few fish remained in the stream the second summer‐autumn, and the production was 1.0 g m−2.
Adrenergic responses and the Root effect in erythrocytes of freshwater fish
Authors: Cossins A. R. , Kilbey R. V.
Published: January 2006

The effects of adrenergic‐stimulation upon the oxygen‐binding capacity of fish erythrocytes have been investigated. The oxygen capacity of rainbow trout, Oncorhynchus mykiss (Walbaum), erythrocytes was lowered by 44% on extracellular acidification (the so‐called ‘Root effect’). Addition of isoproterenol at 20° Ccaused an acid shift of the curve relating oxygen capacity to pH0 by approximately 0.2 pH units, a value which was similar to the change in intracellular pH caused by adrenergic stimulation (Cossins & Kilbey Journal of Experimental Biology, 148, 303–312, 1990). Moreover, when plotted as a function of pHi, the curves for control and adrenalinstimulated erythrocytes were superimposable suggesting that the adrenergic shift in the Root curve was a result of the change in pHi caused by activation of the adrenergic Na+/H+ exchanger.

A similarly large adrenergic shift in the Root curve was observed for pike, Esox lucius L., erythrocytes, though not for erythrocytes of carp, Cyprinus carpio L., and tench, Tinea tinea (L.). The pH for the mid‐point of the Root effect in pike erythrocytes was distinctly more acid than for trout, but in both cases corresponded closely with the optimal pH for the adrenergic Na+/H+ exchange mechanism. This suggests a link between the functional characteristics of the exchanger and the oxygen‐binding properties of haemoglobin.
Ontogenetic change in the relationship between metabolic rate and body mass in a sea bream Pagrus major (Temminck & Schlegel)
Authors: Oikawa S. , Itazawa Y. , Gotoh M.
Published: January 2006

Ontogenetic changes in the relationship between resting rate of oxygen consumption and wet body mass were examined at 20° C with the sea bream Pagrus major ranging from 0.00020 g (weight just after hatching) to 270 g (weight at 530 days old). There was a triphasic relationship between oxygen consumption of an individual fish M (μl min−1) and body mass W(g). During a very early stage (weight 0.00020–0.00025 g), corresponding to the pre‐larval stage and with the transitional period to the post‐larval stage, there was no substantial change in body mass. The mass–specific metabolic rate M/W (μl g−1 min 1) showed no clear relationship to body mass as expressed by the equation M/ W=4.86 + 1.47 D, where D is age in days. During the post‐larval stage (weight 0.00031–0.005 g), M/W remained almost constant independent of body mass following the expression M= 12.5 W0.949. During the juvenile and later stages (weight 0.005–270 g), M/ W decreased with increasing body mass following the expression M= 6.3 W0.821 which is significantly different from the expression for the post‐larval stage (P < 0.001). Ontogenetic changes in the metabolism‐body mass relationship are discussed from the viewpoint of relative growth of organs with different metabolic activities.
Mechanisms of aluminium extraction and accumulation at the gills of rainbow trout, Oncorhynchus mykiss (Walbaum), in acidic soft water
Authors: Playle R. C. , Wood C. M.
Published: January 2006

Rainbow trout were fitted with latex masks for the measurement of ventilatory flow rate (V̇w) and with opercular catheters for sampling expired water from close to the branchial surface. Fish were exposed for 6 h to pH 5.1, 4.7 or 4.1 in the presence (138 μg l 1) or nominal absence (1 μg 1–1) of Al. Inspired and expired Al concentrations and water pH were measured via the opercular catheters. Gills were sampled for accumulated Al at the end of the experiments. V̇w increased during Al exposures at all three pHs. However, in the absence of Al, V̇w increased only at pH 4.1. Aluminium extraction from the water and Al accumulation on the gills were highest at inspired pH 5.1 and lowest at pH 4.1, and correlated well with expired pH, which was 0.2–0.7 pH units higher than inspired pH. Gill Al accumulations amounted to only about one‐tenth of deposition calculated from Al extraction from the water and V̇w, and gill Al was tightly bound to the branchial surface.

Calculations of Al solubility, oversaturation, and species composition were made using measured expired pH values, and were compared with Al extraction from the water and measured gill Al concentrations. In general, these analyses indicated that reduced Al solubility near the gills is a reasonable explanation of Al extraction from the water, and that Al(OH)2+ and Al(OH)3° are the Al species most likely to interact initially at the gills. It is suggested that mucus sloughing removes most precipitated Al, and that only the charged form persists, bound to structural elements on the gill surface. A model incorporating these results, and pH changes in the fish gill micro‐environment in general, is presented to explain previously‐reported ionoregulatory and respiratory effects of Al.
Biology of the sweeper,Pempheris vanicolensisCuvier & Valenciennes, a Lessepsian migrant in the eastern Mediterranean, with a comparison with the original Red Sea population
Authors: Golani D. , Diamant A.
Published: January 2006

Various aspects of the biology ofPempheris vanicolensisCuvier & Valenciennes, a recent Lessepsian (Suez Canal) immigrant into the Mediterranean, are given. Red Sea and Mediterranean populations were compared, and the results indicate that the spawning season is shortened in the Mediterranean, continuing from April to September, as opposed to year‐round in the Red Sea. Descriptions of a ripe ovary and post‐larva from the Mediterranean are given. Individuals reach a mean size of 108 mm (t.l.) in their first year, and 144 mm in the second year. Little change has occurred in the diet of the immigrant population, and both populations feed nocturnally, chiefly on larval and adult stages of planktonic crustaceans. Direct underwater observations on the diurnal behaviour of the species show that the fish leave their daytime cave shelter at sunset, congregate at a nearby site and then migrate inshore and disperse into small groups to feed. Before dawn, they reassemble at the cave's entrance, and finally enter it at sunrise, after the school has built up. Observations on Mediterranean sweepers show that the fish are segregated into size groups, ranging from 30 mm juveniles in the high littoral to 100–150 mm adults at depths of 4–5 m.
A comparison of circatidal rhythmicity and entrainment by hydrostatic pressure cycles in the rock goby, Gobius paganellus L. and the shanny, Lipophrys pholis (L.)
Authors: Northcott S. J.
Published: January 2006

The intertidal teleosts Gobius paganellus and Lipophrys pholis show endogenous circatidal activity rhythms when recorded in constant conditions. Under these conditions, the rhythm of L. pholis is the more precise which may indicate stronger coupling between underlying circalunadian oscillators in this species. In G. pagunellus the inter‐oscillator coupling may be weaker and this could enable a more subtle interpretation of tidal fluctuations than in L. pholis. The oscillators may, however, be fundamentally different in the two species; circalunadian in G. paganellus and circatidal in L. pholis.

When exposed to hydrostatic pressure cycles of tidal frequency both species responded pre‐ dominantly to increasing pressure, which suggests that in the wild they are likely to be most active on the rising tide. Hydrostatic pressure cycles are confirmed as a zeitgeber for both species by the successful entrainment of some individuals. The lack of entrainment of others impIies that additional zeitgebers are required for complete entrainment.
Stocking experiments with 0 + and 1 + trout parr, Salmo trutta L., of wild and hatchery origin: 1. Post‐stocking mortality and smolt yield
Authors: Berg S. , Jorgensen J.
Published: January 2006

Wild and hatchery‐reared 8–12‐month‐old (5–8 cm) trout, Salmo frurta L., were stocked in tributaries of the River Gudenb. Mortality was examined by means of electrofishing. Repeated electrofishing and handling caused a small increase in mortality. The daily instantaneous mortality rate Z was high during the first 2 months after stocking, ranging from 0.0070 for wild trout to 0.0326 for domestic trout at a stocking density of one trout per m2 and from 0.0206 (wild trout) to 0.0888 (domestic trout) at a stocking density of two trout per m2. Two months after stocking, Z decreased drastically ranging from 0.0007 (wild trout) to 0.0067 (domestic trout). When stocked, first‐generation hatchery trout showed Z equal to domestic trout. Wild trout resident in the experimental stream were negatively affected by the introduction of domestic trout and wild trout from another stream. at a stocking density above the carrying capacity. It is concluded that the higher mortality of domestic trout was caused by changes in food, feeding and exercise, possibly combined with the lack of selection in the hatchery. Smolt yield at age 2+ was 3.2% (0+ trout stocked in the fall)‐7.0% (1 + trout stocked in the spring) of the domestic trout stocked (approx. one‐sixth to one‐third of natural populations) and 65.2–68.7% of the domestic trout present before the smolt run. For first generation hatchery trout of wild origin the corresponding figures were 7.3% (age 0 +) and 93.4%, and for wild trout introduced to the experimental stream they were 11.1% (age0 +)and39.8%.
Identification of a new granulocyte type in the skin of carp Cyprinus carpio (L.)
Authors: Cross M. L. , Matthews R. A.
Published: January 2006

The skin of carp Cyprinus carpio (L.) was investigated by electron microscopy. A new granulocyte cell type was identified, and is described as being similar to the eosinophilic granular cell (EGC) of salmonids.
Behavioural thermoregulation and homing by spring chinook salmon,Oncorhynchus tshawytscha(Walbaum), in the Yakima River
Authors: Berman C. H. , Quinn T. P.
Published: January 2006

Temperature‐sensitive radio transmitters were employed to study the patterns of behavioural thermoregulation, habitat preference and movement of 19 adult spring chinook salmon,Oncurhynchus tshawytscha(Walbaum), in the Yakima River. During the 4 months prior to spawning, fish maintained an average internal temperature 2.5°C below ambient river temperature. This represented a 12 to 20% decrease in basal metabolic demand or a saving of 17.3 to 29.9 calkg−1h−1. Fish were most commonly associated with islands, pools, and rock out‐croppings along stream banks. Homing behaviour appeared to be modified to optimize temperature regimes and energy conservation. As the time of spawning approached, fish left thermal refuges and migrated to spawning grounds upstream and downstream of refuge areas. Although spring chinook salmon residing within cool‐water refuges may be capable of mitigating sub‐lethal temperature effects, cool‐water areas need to be abundant and available to the fish. The availability of suitable thermal refuges and appropriate holding habitat within mainstem rivers may affect long‐term population survival.
Cortisol stimulates hypo‐osmoregulatory ability in Atlantic salmon, Salmo salar L.
Authors: Bisbal G. A. , Specker J. L.
Published: January 2006

Hypo‐osmoregulatory ability in juvenile Atlantic salmon, Sulrno salur L., was improved by cortisol treatment. Implantation of a vegetable shortening pellet containing cortisol (50 mg kg−1) resulted in elevated plasma cortisol titres. Maximum cortisol levels (160–170ngml−1) were observed at days 6 and 12 after the implantation and dropped significantly by day 55. Cortisol‐implanted fish in fresh water developed a twofold increase in gill Na+/K+‐ATPase activity at days 6 and 12, and a threefold increase by day 55. Intestinal mucosa Na+/K+‐ATPase activity was not affected by cortisol. Cortisol‐implanted fish exposed to 28 ppt sea water for 48 h tended to show an improved ability to regulate their plasma osmolarity and reduce their ionic load. The osmo‐regulatory ability attained at days 12 and 55 was further evaluated by exposing fish to 37 ppt sea water for 96 h. While all the control fish died relatively early in these tests, cortisol‐implanted fish showed a clear reduction in their mortality rate. These results indicate that cortisol can induce biochemical and organismal changes during winter months that typify preadaptive events normally occurring in the spring.
Sexual maturity in sea trout, Salmo trutta L., running up the River Calonne (Normandy, France) at the ‘finnock’ stage
Authors: Maisse G. , Mourot B. , Breton B. , Fostier A. , Marcuzzi O. , Le Bail P. Y. , Baglinière J. L. , Richard A.
Published: January 2006

Sexual maturation in sea trout (Salmo trutto L.) running up the River Calonne (Normandy, France), at the finnock stage, is characterized. Autopsy of 118 finnock in summer showed that 87 ± 7% aged 2+ and 33 ± 15% aged 1 + were undergoing gametogenesis. In autumn all the fish were maturing. The analysis of plasma levels of 11‐ketotestosterone, 17β‐oestradiol, maturational gonadotropin and vitellogenin showed that only females in vitellogenesis can be well identified in summer (plasma vitellogenin greater than 0.30 mg ml‐1). The morphological recognition of females among 134 autumn finnock and the ELISA assay of plasma vitellogenin of 814 summer finnock, demonstrated that vitellogenic females represented 12 ± 2%0 of the 1 + individuals and 46 ± 2% of 2+ fish captured during the 1985 run. The question of a possible relationship between the salinity tolerance ofjuvenile trout migrating towards the sea in the spring and their age on first migration in the river is discussed.
School size affects individual feeding success in three‐spined sticklebacks (Gastevosteus aculeatus L.)
Authors: Ranta E. , Kaitala V.
Published: January 2006

The effect of school size on the feeding success of individual three‐spined sticklebacks was studied. We found that the proportion of fish feeding on benthic prey increased with school size and that fish in large schools tended to start feeding sooner than fish in small schools. The total number of strikes also increased in larger schools. Despite this evidence for a foraging benefit associated with school membership we propose that improved feeding returns do not alone explain stickleback schooling.
Accumulation and effects of aluminium in the minnow (Phoxinus phoxinus L.) at different pH levels
Authors: Norrgren L. , Wicklund Gl A. , Malmborg O.
Published: January 2006

The accumulation and effects of 150 pg All‐1 on minnows (Phoxinus phoxinusL.) were studied in soft water at pH 7, 6 and 5. The fish were kept in a flow‐through water system for up to 48 days. Addition of aluminium to the water resulted in poor appetite, passivity and a tendency for the fish to gather as far as possible from the aluminium inlet. The mortality was high at pH 5 and also after addition of aluminium at pH 6. Severe lesions were noted in the gills and olfactory organs after exposure to aluminium. The concentration of aluminium in the gills, liver and kidney was increased at low pH. A large proportion of the aluminium was located on the surface of the gill epithelium. The recovery capacity was pronounced when the aluminium exposure was terminated and the pH was increased from 5 to 7. No further mortality occurred and gill and olfactory organ structure returned to near normality in about 36 days.
Occurrence and seasonal dynamics of Pseudodactylogyrus anguillae (Yin & Sproston) (Monogenea) in eel, Anguilla anguilla (L.), in England
Authors: Nie P. , Kennedy C. R.
Published: January 2006

Established populations of Pseudodacrylogyrus anguillae are reported from eels in England for the first time. Prevalence and abundance peak in late summer in all three localities and the parasite overwinters at low levels on eels.
Genetic stock structure of odd‐year pink salmon, Oncorhynchus gorbuscha (Walbaum), from Washington and British Columbia and potential mixed‐stock fisheries applications
Authors: Shaklee J. B. , Klaybor D. C. , Young S. , White B.A
Published: January 2006

We used electrophoresis to determine the number and characteristics of genetically distinct stocks of odd‐year pink salmon in Washington and southern British Columbia. We analysed 5128 fish from 52 collections (taken in 1985, 1987 and 1989). We observed genetic variation at 53 enzyme‐coding loci, 19 of which were polymorphic at the Po‐95 level in at least one stock. Genotypic proportions conformed to Hardy‐Weinberg expectations in nearly all cases. The genetic profiles of individual populations were generally stable over the three cycle years studied. Significant differences in allele frequencies at sAAT‐3*, PEP‐LT* and PGDH* for several stocks were, however, noted between this study and previously reported data for pink salmon. We used G‐tests and cluster analysis of genetic distances to evaluate genetic interrelationships among collections and to define genetically distinct stocks. Differentiation among stocks exhibited a clear geographic pattern with three major clusters of stocks recognizable: (1) Hood Canal and Washington Strait of Juan de Fuca stocks, (2) Puget Sound, Fraser River, and southern Canada South Coast stocks, and (3) northern Canada South Coast stocks and Canada North Coast stocks. Computer simulations using 14 and 28 loci, and sample sizes of 15C600, demonstrated that accurate estimates of stock‐group composition could be obtained for pink salmon fisheries having a considerable range of stock compositions. The simulations revealed that approximately 50% fewer fish were required to obtain a given level of precision of stock group composition estimates with 28 loci as with the set of 14 loci used in previous investigations.
Failure of a stocking policy, of hatchery reared brown trout, Salmo trutta L., in Asturias, Spain, detected using LDH‐5* as a genetic marker
Authors: Morán P. , Pendás A. M. , Garcia‐Vázquez E. , Izquierdo J.
Published: January 2006

A useful genetic marker exists through the apparent fixation of the LDH‐5*100 allele in wild populations of brown trout in rivers from Asturias, Spain, contrasted with the near fixation of the LDH‐5*90 allele in hatchery populations used to stock these rivers. In sampling locations where natural reproduction occurred, the *100 allele was found exclusively in all areas having no record of hatchery stocking. The *100 allele also predominated in three stocked areas having natural reproduction; in two of these areas a few individuals of the 0 + age class were homozygous for the *90 allele. These data indicated that all catchable and reproductive fish originated from indigenous populations and thus the policy of hatchery supplementation was a failure in these areas.
Fine‐spotted brown trout: genetic aspects and the need for conservation
Authors: Skaala Ø. , Jørstad K. E. , Borgstrøm R.
Published: January 2006

In Lake Svartavasstjønn on the Hardangervidda plateau, a fine‐spotted variant of brown trout has been found. The spotted variability shows a classical Mendelian mode of inheritance. In this population genetic variability was found in LDH‐5*, MDH‐3* and MDH‐3*. The fast allele at LDH‐5* had a frequency of 0,913. This is remarkable, as this allele has been found in frequencies above 0.4 in only five out of 50 investigated populations in Norway. The genetic characteristics of brown trout from Lake Svartavasstjønn were compared with 11 other populations sampled from a broad geographical area of Norway. Among these was Lake Setningen, where fine‐spotted individuals occur at low frequency. Using a cluster analysis based on eight loci found to be polymorphic in brown trout, we found no indication of a close relationship between the fine‐spotted brown trout from Lake Svartavasstjønn and the population in Lake Setningen. During a field survey in 1990 we found that the reproduction of fine‐spotted trout in Lake Svartavasstjønn had terminated. The fine‐spotted trout represents a valuable but threatened genetic resource, and attempts are carried out to conserve it.
Repetitive DNA sequences and the divergence offish populations: some hopeful beginnings
Authors: Turner B. J. , Elder J. F. , Lauchlin T. F.
Published: January 2006

Repetitive sequences are predominant components of eukaryotic genomes, including those of fishes, but they represent largely unchartered territory for the student of fish evolution and population differentiation. Three examples of the use of repetitive sequences are presented. In one, a Hind 111 monomeric unit of an adjacent repeat (satellite) sequence was characterized, by cloning and sequencing, from the genome of the sheepshead minnow, Cyprinodon variegates, a species which ranges from Cape Cod to Mexico. The characteristic monomeric sequence of each population sample (termed the ‘canonical sequence’) is divergent. The data demonstrate that molecular drive, usually invoked only for interspecific divergence, can apparently produce characteristic suites of repetitive sequences in conspecific local populations. The two other examples deal with dispersed simple‐sequences and minisatellites which provide individual‐specific DNA fingerprint phenotypes. In both cases, previous allozyme studies failed to resolve potentially important variation. In Rivulus marmoratus, a selling hermaphroditic species with homozygous, clonal population structure, fingerprinting demonstrates unprecedented levels of intrapopulation genetic heterogeneity, and strongly suggests that there are significant mutational distances between even sympatric clones. The data warrant serious re‐evaluation of the genetic variation of this species, its adaptive significance and its origins. In the striped bass, Morone saxatilis, a species of enormous economic and recreational importance, fingerprinting demonstrates that even hatchery stocks have very high levels of genetic variation. Though the species essentially lacks allozyme variation, it is apparently not approaching genome‐wide homozygosity. Taken together, the data argue that the analyses of various kinds of repetitive sequences will play an increasingly greater role in future attempts to understand the structure and differentiation offish populations.
Genetic protein variation and natural selection in Atlantic salmon (Salmo salav, L.) parr
Authors: Jordan W. C. , Youngson A. F.
Published: January 2006

The principal focus of this study was an examination of the relationship between diallelic variation at the MEP‐2* locus and growth and survival in Atlantic salmon parr. In addition, patterns of growth and survival among genotypes at the AAT‐I*, IDDH‐I* and ZDHP‐2* loci were also examined. Significant differences in growth were found among MEP‐2* genotypes, with *100/ 100 homozygotes largest in one of two independent comparisons and the *125/I25 homozygotes largest in the other. No growth differences were observed among genotypes at any other locus. Although no significant differences were found in survival among genotypes at any locus, results of joint analysis of the patterns of growth and survival among MEP‐2* genotypes were consistent with a model of positive size‐selective mortality. The demonstration of growth differences among MEP‐2* genotypes in parr and smolts may indicate an association between selection on this locus in fresh water and previously reported differences in sea‐age at maturity among MEP‐2* genotypes in Atlantic salmon.
Genetic changes in a vendaceCovegonus albula(L.) population, 92 years after introduction
Authors: Vuorinen Jukka , Næsje Tor F. , Sandlundt Odd Terje
Published: January 2006

The Osensjmn vendace,Coregonus albula(L.), population was founded in 1895 by introduction of about 90 000 fry from Lake Mjøsa. After 92 years, or about 46 generations of isolation, remarkable genetic changes were evident among the transplants compared to their source population. Electrophoresis of 33 enzyme loci revealed that allele frequencies differed significantly in eight of the 10 polymorphic loci. Nei's unbiased genetic distance wasD= 0.012, representing the level of population differentiation usually observed among distant watercourses in vendace. Genetic variability was clearly higher among the transplants: average observed heterozygosity was 14.8% compared with 11.2% among Lake Mjøsa vendace. The high genetic variation among Osensjoen vendace shows that the divergence is not due to a small number of founders or bottlenecks in later generations. Selection by the contrasting environmental conditions between the habitats of the donor and transplanted populations is the most plausible hypothesis to explain the genetic changes in the Osensjsen vendace.
Population differentiation in Trinidadian guppies (Poecilia reticulata): patterns and problems
Authors: Shaw P. W. , Carvalho G. R. , Magurran A. E. , Seghers B. H.
Published: January 2006

Populations of the guppy, Poecilia reficulata, in N. Trinidad exhibit marked population differentiation in allozyme frequencies. Here we investigate six further populations electrophoretically at 25 enzyme‐coding loci to examine patterns in geographical structuring, genotypic distributions and genetic diversity. With one exception, possibly related to an experimental introduction, populations divided broadly (dendrogram of Nei's mean genetic identity, Ī) in accordance with proposed ancestral colonization. Most populations were in Hardy Weinberg equilibrium, though some significant deficits in heterozygotes were detected. Incorporating information from published data, markedly hjgher levels of genetic diversity (mean observed heterozygosity, H̄o) were recorded in lowland [H̄o= 0.0382 ± k0406 (s.e.), n= 9] compared with upstream populations [H̄o= 0.0112 ± 00034 (S.E.), n = 9]. Patterns are discussed in relation to historical and present‐day evolutionary forces.
Phylogenetic relationships among four members of Stizostedion (Percidae) determined by mitochondrial DNA and allozyme analyses
Authors: Billington N. , Danzmann R. G. , Hebert P. D. N. , Wards R. D.
Published: January 2006

Phylogenetic relationships among four Stizostedion species were examined using mitochondrial DNA (mtDNA) and allozyme analyses. Twenty‐six allozyme loci were scored, and mtDNA variation was examined using 24 restriction endonucleases, yielding 48–57 restriction sites among the species. Genetic distance analyses show that the two North American species (S. canadense and S. vitreum) cluster in one group, while the two European species (S. hciopercu and S. vogense) form a second group. Nei's genetic distance between these two groups was 0.7 ± 0.2 for allozymes, while the corresponding mtDNA sequence divergence was 14.8 ± 2.0%, suggesting that these two groups diverged approximately 10 million years ago. Thus, these data are consistent with the hypothesis that Stizostedion colonized North America during the Pliocene.
A salmon id phylogeny inferred from mitochondrial cytochrome b gene sequences
Authors: Mcveigh H. P. , Davidson W. S.
Published: January 2006

Partial mitochondrial cytochrome b gene sequences of eight salmonid species were used in a PAUP analysis to generate a phylogeny of the group. The four genera represented are Salmo, Salvelinus, Oncorhynchus and Thymallus. The inferred phylogenetic tree coincides well with the classically derived one for these genera. The recent reclassification of the rainbow trout as a member of the genus Oncorhynchus is supported. The assignment of grayling as the outgroup is vindicated. The utility of gene sequence data to infer the phylogenetic relationships of the Salmonidae is discussed.
Retention of intragastric transmitters after voluntary ingestion by captive cod, Gadus morhua L.
Authors: Armstrong J. D. , Johnstone A. D. F. , Lucas M. C.
Published: January 2006

Squid‐encapsulated acoustic transmitters were ingested by Atlantic cod, Gadus morhua, (3128–10 221 g) held in captivity at 12° C. Retention times ranged from 5 to > 21 days. There was no significant change in feeding rate after transmitter ingestion.
Selection of prey from a seagrass/mangrove environment by golden lined whiting, Sillago analis (Whitley)
Authors: Brewer D. T. , Warburton K.
Published: January 2006

Most previous studies of food selection by fishes have been conducted on visually‐feeding species in relatively unstructured environments. The food selection behaviour ofSillago analis(Whitley), feeding nocturnally in a complex seagrass/mangrove environment, was assessed. Crustacean prey were relatively accessible and displayed the highest electivity values. Annelids were usually buried at least 30 mm below the substrate surface and, like potential fish prey, were either not taken or showed consistently negative electivities. Although many mollusc species were accessible, only the siphon tips of the bivalveGlauconome virens(Linnaeus) were positively selected. Results from both field and laboratory indicated thatS. analisis not a strongly size‐selective predator. However, in contrast to the field study, the laboratory results showed thatS. analishad a strong preference for annelids [Marphysa sanguinea(Montague)] as well as crustaceans. The food selection patterns of S. analis could not be clearly described in terms of single parameters such as prey size, prey abundance or prey energy content, which have been used in the context of optimal foraging theory and are often described as strong determinants of food selection in visual predators. Instead, this nocturnally‐feeding species takes a variety of the more vulnerable prey (i.e. those which are spatially accessible, weakly motile or thinly shelled) in an apparently opportunistic fashion.