bluuebunny/crossref_metadata_2025 huggingface dataset:
Do the dietary compositions of Acanthopagrus butcheri in four estuaries and a coastal lake vary with body size and season and within and amongst these water bodies?
Authors: Sarre G. A. , Platell M. E. , Potter I. C.
Published: April 2005

The dietary compositions were determined for Acanthopagrus butcheri in four estuaries and a saline, coastal lake, which vary in the extent, if any, of their connection to the sea and amongst which, in spring and summer, their salinities ranged from 2 to 7‰ in an intermittently open estuary to >40‰ in a normally closed estuary. The dietary compositions of A. butcheri in each of the five water bodies were significantly different, which reflected differences in the abundance of different components of the biota in those systems. Biotic differences amongst water bodies thus accounted for the far larger contributions made to the volume of the stomach contents by the macroalgae Cladophora sp. in the Moore River Estuary on the lower west coast of Australia, by amphipods and decapods in the Swan River Estuary 85 km further south and by polychaetes in the landlocked Lake Clifton a further 85 km further south. The diet of A. butcheri in the Nornalup/Walpole Estuary on the south coast of Western Australia contained atypically large volumes of the seagrass Ruppia megacarpa and teleosts, whereas that in the normally closed Wellstead Estuary, 260 km to the east was characterised by large volumes of the macroalgae Chaetomorpha sp. and a tube‐dwelling amphipod. However, there is evidence that A. butcheri selects certain prey, when two or more of the typical prey of A. butcheri are present in the environment, and that it prefers to feed on or above the substratum, rather than within the substratum. The dietary composition of A. butcheri underwent pronounced ontogenetic changes in each water body, these being progressive in estuaries on the lower west coast and abrupt in those on the south coast. Within the upper Swan Estuary, the dietary composition changed in an upstream direction, reflecting changes in the relative abundance of certain benthic macroinvertebrate prey, but did not undergo conspicuous seasonal changes, which is consistent with the lack of any clear cut seasonal changes in the abundance of their major prey.
State‐dependent spawning migration in Norwegian spring‐spawning herring
Authors: Slotte A. , Fiksen Ø.
Published: April 2005

Norwegian spring‐spawning herringClupea harenguswinter in fjords of northern Norway, whereas the subsequent spawning occurs at various locations along the coast with a main bulk off the south‐western coast. The distance of the southward spawning migration tends to increase with the length and condition of the fish. The costs and benefits of the southward migration were modelled in terms of fitness (number of surviving offspring). The model assumes that larvae have increasing growth and survival rates further south as they pass through warmer water during the northward drift in the coastal current. In agreement with the observed spawning distribution, optimal spawning grounds were predicted off the southwestern coast and farther south with increasing fish length and condition. The present study suggests that homing is not a successful strategy for these herring, and instead the selection of spawning grounds depends on individual internal state (length, condition), the cost of migration and the probability of larval survival.
Post‐release adaptation processes of hatchery‐reared honmasu salmon parr
Authors: Munakata A. , Björnsson B. Th. , Jönsson E. , Amano M. , Ikuta K. , Kitamura S. , Kurokawa T. , Aida K.
Published: April 2005

Hatchery‐reared honmasu salmon Oncorhynchus rhodurus × masou parr released into the Yanagisawa River, Tochigi Prefecture on 24 June 1996 increased significantly in length and weight by November, while siblings retained in hatchery tanks did not. Plasma growth hormone (GH) levels of the released parr increased from 1 day after the release until 23 August, while the GH levels of the wild parr in the river did not increase. The released parr started to consume various natural prey organisms within a day after release. However, stomach fullness of the released parr was considerably lower than that of the wild parr during the first week following release. Trypsin activity in the released parr increased after 23 August, 2 months post‐release. The results demonstrate that the released parr adapt to the natural river environment within weeks. Endocrine control by GH and exocrine pancreas activity appear to play important roles in the post‐release adaptation processes.
Distribution of metals during digestion by cutthroat trout fed benthic invertebrates contaminated in the Clark Fork River, Montana and the Coeur d'Alene River, Idaho, U.S.A., and fed artificially contaminated Artemia
Authors: Farag A. M. , Suedkamp M. J. , Meyer J. S. , Barrows R. , Woodward D. F.
Published: April 2005

The concentrations of essential amino acids in three, undigested invertebrate diets collected from the Clark Fork River (CFR) for cutthroat trout were similar to each other, but were c. 25–75% less than Artemia that were exposed to a mixture of arsenic, copper, cadmium, lead and zinc in the laboratory. The Artemia diet appeared less palatable and the texture, quantity and appearance of the intestinal contents differed between fish fed the Artemia and CFR diets. The Pb% in the fluid fraction of the intestinal contents was greater for the Artemia (29%) than for the CFR diets (10–17%), and the Cu% in the amino acid plus metal fraction of the intestinal contents was greater for the Artemia (78%) than for two of the three CFR diets (67% and 70%). Intestinal contents of fish fed invertebrate diets collected from various sites on the Coeur d'Alene River (CDA), Idaho, were similar in texture, quantity, and appearance. For fish fed the CDA diets, differences in the distribution of metals among fractions of the digestive fluids appeared to be related to concentrations of metals in the invertebrate diets. Pb% was lowest of all metals in the fluid portion of the intestinal contents. However, >80% of all metals in the hind gut were associated with the particulate fraction where they may still be available for uptake through pinocytosis.
The emergence period of sea trout fry in a Lake District stream correlates with the North Atlantic Oscillation
Authors: Elliott J.M. , Hurley M. A. , Maberly S. C.
Published: April 2005

The date of fry emergence over 30 years in a sea trout nursery stream, predicted by an individual‐based model, correlated significantly (r=0·660,P<0·001) with an index of the North Atlantic Oscillation. Water temperature is the main driving variable in the model and stream temperature also correlated significantly (r=0·662,P<0·001) with the index, providing a probable causal link. Therefore, the inter‐annual variations in emergence may not be unique to this one stream, but may be typical of other trout streams with similar climatic conditions.
Retrograde peristalsis; a possible mechanism for filling the pyloric caeca?
Authors: Rønnestad I. , Rojas‐Garcia C. R. , Skadal J.
Published: April 2005

A marked, relatively rapid retrograde peristaltic activity was observed in the pyloric region of Atlantic halibut Hippoglossus hippoglossus in vitro and in vivo. This could provide a mechanism for filling the pyloric caeca, and the retrograde contraction could also be involved in mixing the chyme with digestive secretions in the region of the pyloric caeca.
Seasonal changes in intra‐ and interorgan occurrence of rodlet cells in freshwater bream
Authors: Koponen K. , Myers M. S.
Published: April 2005

Significant seasonal differences in intra‐ and interorgan prevalence, abundance and distribution of rodlet cells (RC) were observed in freshwater bream caught in May and August 1997 from a PCB‐polluted lake, Lake Kernaala, Finland. In May, the majority of RCs in liver were seen in blood vessel endothelium, while in August most cells were located in the epithelium of the intrahepatic biliary ducts. In kidney, a significant increase in RCs in the columnar epithelium of the collecting ducts was observed from May to August. RCs in spleen were extremely rare in May, but were seen frequently in the endothelium of the splenic blood vessels in August. In gill and intestine, RCs were found in every tissue sample studied, with no statistical differences in their abundance or distribution between seasons. No RCs were seen in gonads. Total numbers of RCs increased dramatically from May to August in kidney and in spleen. The frequency of RCs corresponded strongly with the current phase of parasitic infections in liver, kidney, and spleen. It is concluded that RCs play a role in host defence mechanisms in fish, displaying induced expression at the times of peak parasitic prevalences.
Geographic variation in growth and food conversion efficiency of juvenile Atlantic halibut related to latitude
Authors: Jonassen T. M. , Imsland A. K. , Fitzgerald R. , Bonga S. W. , Ham E. V. , Nævdal G. , Stefánsson M. O. , Stefansson S. O.
Published: April 2005

Higher growth capacity and food conversion efficiency was observed in populations of juvenile halibut from high Hippoglossus hippoglossus compared lower latitudes. In addition, temperature adaptation shown by the lower temperature optimum for growth in the Norwegian population (mean±S.E. 12·9±0·10 C) compared with the Icelandic and Canadian populations (14·2±0·2 and 13·9±0±30 C respectively), seems to occur. Overall the data support the hypothesis of countergradient variation in growth. These results have implications firstly for selection focusing on growth performance in halibut culture; and secondly, for safe prediction of growth, since if countergradient variation in growth performance occurs one cannot assume automatically that a species will respond to the same set of physiological parameters in the same way throughout its range.
Mitochondrial cytochrome b DNA sequence variation of Atlantic cod from Iceland and Greenland
Authors: ÁRnason E. , Petersen P. H. , Kristinsson K. , Sigurgíslason H. , Pálsson S.
Published: April 2005

Sequence variation of a 250–bp (base pair) fragment of the mitochondrial cytochrome b gene has been studied using polymerase chain reaction and direct sequencing of 519 Atlantic cod Gadus morhua from Iceland and 78 cod from Greenland. Twenty‐four variable nucleotide sites, mostly silent, define 34 haplotypes. The amount of variation is high (?C=0·73, π=0·52 per 100 bp) with five haplotypes at polymorphic frequencies in Iceland and a number of widely dispersed rather rare haplotypes. A tree of genetic relationships among haplotypes has considerable homoplasy yet it is relatively shallow implying a high turnover of variants of the polymorphism. Net nucleotide genetic divergences among localities are nil. Geographic locality overall area, and inshore/offshore comparison explain none of the variation in an AMOVA, all the variation is among individuals and a null hypothesis of non‐differentiation of haplotype frequencies among localities or overall areas cannot be rejected. A temporal year‐class effect is found. The evolutionary difference between Greenland and Iceland cod is not significant and the percentage of variation accounted for by the Greenland/Iceland difference is half of what a temporal effect within Iceland explains. There is no evidence for considering the cod at Greenland and Iceland to consist of separate evolutionary units and the question of separate management units must address the lack of diagnostic genotypes and evidence for gene flow from clinal variation.
Growth rate, age and size of bonefish from the Gulf of California
Authors: Pfeiler E. , Padrón D. , Crabtree R. E.
Published: April 2005

Growth rates of cultured first‐year bonefish Albula sp. averaged 0·32 mm day−1. Maximum theoretical growth (±95% CI) was 278 (±11·2) mm LS (sexes combined), confirming that Albula sp. from the Gulf of California grow less than other species in the‘vulpes’complex.
Nuclear and mitochondrial DNA analyses reveal four genetically separated breeding units of the swordfish
Authors: Chow S. , Takeyama H.
Published: April 2005

Variants in the calmodulin gene intron 4 (CaM) and the mtDNA D‐loop region (D‐loop) detected by RFLP and nucleotide sequence analyses were used to investigate the global stock structure of the swordfish Xiphias gladius. Two alleles (A and B) were observed at the CaM locus among 8 samples (Mediterranean, Tarifa, four Atlantic areas, Indian and Pacific oceans) comprising 567 individuals. Genotype distributions at this locus within samples were in accordance with Hardy‐Weinberg equilibrium. Significant differences in allele frequencies were observed between Mediterranean‐Northwest Atlantic samples (A=0·347–0·493) and those from tropical Atlantic and Indo‐Pacific (A=0·81–1). In the D‐loop region, Alu I and Rsa I digestions detected 4 (A‐D) and 8 (A‐H) genotypes, respectively. The frequency of type C for Alu I was lower in Indo‐Pacific samples (0·2) than Atlantic and Mediterranean samples (0·365–0·643). Frequency of type C for Rsa I increased from the Pacific (0·398) to the Northwest Atlantic (0·698) and Tarifa (0·949) samples, and the Mediterranean sample was fixed for type C. These samples were classified into three groups (Mediterranean‐Tarifa, Atlantic and Indo‐Pacific) using a heterogeneity test of mtDNA genotype distributions. Combined analysis of the CaM and D‐loop loci indicated that there are at least four breeding units: Mediterranean, northwestern Atlantic, tropical to South Atlantic, and Indo‐Pacific.
Hormonal regulation of the European sea bass reproductive cycle: an individualized female approach
Authors: Asturiano J. F. , Sorbera L. A. , Ramos J. , Kime D. E. , Carrilo M. , Zanuy S.
Published: April 2005

Fifteen tagged female sea bass Dicentrarchus labrax were sampled weekly from September to April and plasma vitellogenin (VTG), testosterone (T), 17β‐estradiol (E2), and two potential maturation inducing steroids (MISs): 17,20β‐dihydroxy‐4‐pregnen‐3‐one (17,20βP) and 17,20β,21‐trihydroxy‐4‐pregnen‐3‐one (20βS) assayed. An oocyte sample was obtained via intraovarian cannulation at each sampling time from every female and the stage of development of the most advanced clutch of oocytes determined and related to VTG and hormone plasma levels for each female. The mean number of ovulations per female was 1·75+0·25 when those females that did not present ovulations were excluded and up to 4 ovulations detected in some females. The highest plasma levels of T (c. 6 ng ml‐1) were observed during postvitellogenesis and the beginning of maturation while maximum plasma levels of E2 (>5 ng ml‐1) were obtained during late vitellogenesis. VTG plasma levels increased throughout vitellogenesis peaking (c. 2·5 mg ml‐1) at postvittelogenesis. For the first time significant changes of plasma progestogens were detected in European sea bass during the sexual cycle. The highest plasma level of 17,20βP (c. 1·1 ng ml‐1) was observed during postvitellogenesis while the highest level of 20βS (c. 1·4 ng ml‐1) coincided with final maturation. These results suggest that 17,20βP and 20βS play a role in the early and final maturation, respectively, in the European sea bass.
Ontogenetic changes of learning capability and stress recovery in Pacific threadfin juveniles
Authors: Masuda R. , Ziemann D. A.
Published: April 2005

Time taken by Pacific threadfin Polydactylus sexfilis juveniles to learn a conditioning reward was taken as the criterion for learning capability. Fish of 50 mm and 90 mm LF had a better learning capability than did smaller (22 mm, 36 mm) or larger (130 mm) size classes. Larger fish (90 mm and 130 mm) were quicker to recover from handling stress than were smaller fish. Based on these experiments it is suggested that 90 mm size class should have the highest adaptability when released into the wild.
Sediment selection in juvenile plaice and its behavioural basis
Authors: Gibson R.N. , Robb L.
Published: April 2005

In the laboratory juvenile plaicePleuronectes platessa(13–114 mm) were consistently found on the finest of four sediments after 24 h both in the light and the dark. Preference when assessed both by the fish's final position and by the amount of time it spent on each sediment agreed on 72% of occasions. Size did not affect preference, which was determined principally by a fish's ability to bury in a sediment. Burial reduces activity and thereby increases the time that fish spend on sediments in which they can bury. Activity level, which is dependent on light intensity and endogenous factors, therefore determines the degree of selectivity shown. Swimming duration and resting by the largest fish (71–114 mm) did not differ among sediments. Field experiments produced results similar to those obtained in the laboratory.
A preliminary investigation to compare metabolic heat dissipation by quiescent and activated spermatozoa of landlocked salmon
Authors: Penttinen O‐P. , Hyväurinen H. , Piironen J.
Published: April 2005

Variation of metabolic heat dissipation between quiescent and active spermatozoa of Salmo salar m. sebago was investigated by direct calorimetry. The technique offers some promise to monitor energy metabolism of teleost sperm.
Southernmost occurrence of the aguavina on the western Atlantic coast of Argentina
Authors: Figurroa D. E. , Diaz De Astarloa J. M. , Ccousseau M. B.
Published: April 2005

The southernmost record of aguavina Diplectrum radiale(Quoy & Gaimard, 1824) is reported for the American Atlantic coast, from Mar Chiquita lagoon, Argentina.
Muscle fibre types and size distribution in sub‐antarctic notothenioid fishes
Authors: Fernandez D. A. , Calvo J. , Franklin C. E. , Johnston I. A.
Published: April 2005

The presumptive tonic muscles fibres of Cottoperca gobio, Champsocephalus esox, Harpagifer bispinis, Eleginops maclovinus, Patagontothen tessellata, P. cornucola and Paranotothenia magellanica stained weakly or were unstained for glycogen, lipid, succinic dehydrogenase (SDHase) and myosin ATPase (mATPase) activity. Slow, intermediate and fast twitch muscle fibres, distinguished on the basis of the pH stability of their mATPases, showed intense, moderate and low staining activity for SDHase, respectively. Slow fibres were the major component of the pectoral fin adductor profundis muscle. The proportion of different muscle fibre types varied from the proximal to distal end of the muscle, but showed relatively little variation between species. The myotomes contained a lateral superficial strip of red muscle composed of presumptive tonic, slow twitch and intermediate fibres, thickening to a major wedge at the horizontal septum. All species also had characteristic secondary dorsal and ventral wedges of red muscle. The relative abundance and localization of muscle fibre types in the red muscle varied between species and with body size in the protandric hermaphrodite E. maclovinus. The frequency distribution of diameters for fast twitch muscle fibres, the major component of deep white muscle, was determined in fish of a range of body sizes. The absence of fibres <20 μm diameter was used as a criterion for the cessation of muscle fibre recruitment. Fibre recruitment had stopped in P. tessellata of 13·8 cm LT and E. maclovinus of 32·8 cm LT, equivalent to 49 and 36·5% of their recorded maximum sizes respectively. As a result in 20‐cm P. tessellata, the maximum fibre diameter was 300 μm and 36% of fibres were in excess of 200 μm. The unusually large maximum fibre diameter, the general arrangement of the red muscle layer and the extreme pH lability of the mATPase of fast twitch fibres are all common characters of the sub‐Antarctic and Antarctic Notothenioids, including Cottoperca gobio, the suggested sister group to the Notothenidae.
Aspects of the early life history of European hake from the central Adriatic
Authors: Arneri E. , Morales‐Nin B.
Published: April 2005

During early development, the left and right sagittae of European hake Merluccius merluccius showed dimorphism in both size and shape due to the different number and size of accessory primordia. Juvenile hake reached the total length (LT) of 15 cm in c. 1 year, with monthly growth rates ranging from 1·6 cm month‐1 in the third month of life to 1·1 cm month‐1 towards the end of the first year. Back‐calculated hatch‐date distribution indicated continuous spawning with a peak in summer and a second, less evident, peak in February–March. The presence of early demersal juveniles (16–30 mm LT, c. 40 days old) very close to the Pomo pit area (Central Adriatic Sea) at c. 140 m depths indicates that the change from the pelagic to the demersal phase takes place at c. 40 days close to the area of concentration of juveniles. The daily‐increment hypothesis was validated indirectly.
Shoaling behaviour of the two‐spotted goby
Authors: Svensson P. A. , Barber I. , Forsgren E.
Published: April 2005

Naturally formed shoals of adult Gobiusculus flavescens in a Swedish fjord ranged in size from a few individuals to several hundred fish and were sorted by body size. Shoal composition was highly dynamic and any particular group was unlikely to remain together for more than a few hours. Shoaling tendency of juveniles in laboratory experiments was high, and consistent preferences were demonstrated for numerically larger shoals. Large test fish preferred to associate with shoals composed of large, over shoals composed of small fish, whereas small test fish associated with both size classes equally. The ecological importance of shoaling in small shallow water fish is discussed, and possible mechanisms for the observed patterns are proposed.
Increased turning per unit distance as an area‐restricted search mechanism in a pause‐travel predator, juvenile plaice, foraging for buried bivalves
Authors: Hill S. , Burrows M. T. , Hughes R. N.
Published: April 2005

During searching, discovery of a prey patch by juvenile plaice Pleuronectes platessa was associated with a change from extensive to intensive search behaviour several moves before an attack on a prey. Intensive search behaviour was characterized by reduced distance of moves, a greater rate of turning per unit distance and shorter pauses between moves. The increase in turn rate was associated with area‐restricted seaching, while a decrease in distances moved suggests that plaice search more efficiently for prey when stationary than while moving. The klinokinetic mechanism that appears to regulate search behaviour in juvenile plaice should allow efficient exploitation of a range of prey distribution patterns based on localized cues alone. Such a mechanism is especially useful to a migratory predator, like plaice, whose foraging is subject to time constraints imposed by tidally available feeding areas.
Contribution to the phylogeny of pangasiid catfishes based on allozymes and mitochondrial DNA
Authors: Pouyaud L. , Teugels G. G. , Gustiano R. , Legendre M.
Published: April 2005

Phylogenetic inferences based on molecular data provide support for the recognition of some Pangasius subgenera and, or species groups as distinct genera. It is suggested that Pangasiidae and Schilbeidae have diverged from a common ancestor probably since late Miocene. Moreover, the data provide evidence for the existence of two distinct episodes of speciation in Pangasiidae. The most ancient occurred in the middle Miocene and concerned emergence of the different genera, while the second referred to an intense speciation event in the genus Pangasius, probably between the early Miocene and the late Pliocene. Finally, this study revealed the existence of two new species of Pangasius.
Influence of growth rate on white muscle dynamics in rainbow trout and brook trout
Authors: Rasmussen R. S. , Ostenfeld T. H.
Published: April 2005

In trout, fast growth stimulated white muscle fibre hypertrophy (P 0·001) and hyperplasia (P<0·01) in outer fibres but not in deep fibres. Glycogen was most prevalent in outer fibres (P<0·01) and in brook trout (P<0·01) that on average had three to four times larger fibres than rainbow trout.
Partial molecular cloning and tissue distribution of hexokinase I cDNA in common carp
Authors: Blin C. , Panerat S. , Kaushik S. , Krishnamoorthy R.
Published: April 2005

The full C‐terminal half of HK‐I cDNA was cloned from common carp Cyprinus carpio. This HK‐I cDNA is homologous to mammalian HK‐I, in its sequence and tissue distribution and probably derives from duplication and fusion of an ancestral gene.
Helminth communities of native and introduced fishes in Lake Pátzcuaro, Michoacán, México
Authors: de Leóan G. Péarez‐Ponce , Garcíaa‐Prieto L. , Leóan‐Réggagnon V. , Choudhury A.
Published: April 2005

In Lake Pátzcuaro in the Mesa Central of México, a total of 19 species of helminths was found in 598 fishes and comprised five digeneans, two monogeneans, four cestodes, one acanthocephalan and seven nematodes, of which ten species were represented by larval or immature states. The richest and most diverse helminth communities were found in the native carnivorous goodeid Alloophorus robustus. In general, the helminth communities in the different fish species were not particularly species rich and the parasite assemblages were numerically dominated by larvae of the bird trematode, Posthodiplostomum minimum. Patterns of helminth community richness and diversity were similar to those previously observed in north‐temperate freshwater fishes. Most enteric helminths occurred with low abundance and only a small proportion of the gut helminth communities was numerically dominated by any one species. Helminths dominating their enteric communities showed some level of host specificity. Helminth communities in carnivorous fish species were generally richer than those in herbivores and detritivores, with the exception of the predominantly herbivorous Goodea atripinnis. The helminth fauna of introduced fishes, Cyprinus carpio, Micropterus salmoides and Oreochromis niloticus, consisted of either few or no host‐specific adult helminth(s) translocated from their original geographical areas and by larval stages of helminths of piscivorous birds. Based on the geological history of the area and the biogeography of the endemic fish fauna, it is hypothesized that host‐switching and relationships with the nearctic fauna have been fundamental in determining the helminth fauna of the endemic fish hosts.
The effects of capture, handling, confinement and ectoparasite load on plasma levels of cortisol, glucose and lactate in the coral reef fish Hemigymnus melapterus
Authors: Grutter A. S. , Pankhurst N. W.
Published: April 2005

Tropical labrids Hemigymnus melapterus sampled underwater had low plasma levels of cortisol, glucose, and lactate. Plasma cortisol levels were elevated by capture stress within 5–6 min, while glucose and lactate levels were not. Plasmalevels of cortisol and glucose increased after 2–4 h of handling and transport to the laboratory. Levels of cortisol and glucose fell with laboratory acclimation back to values similar to those found in wild fish. Parasitism by gnathiid isopods across an order of magnitude of isopod numbers had no effect on plasma levels of cortisol or glucose. Thus, H. melapterus has a stress response similar to that shown by temperate species, and relatively high parasite loads are not apparently stressful to fish in the wild. This may be related to the counterproductive effects of physiological stress responses on the immune system or behaviour‐modulated processes that counter parasitic invasion.
Effects of 11‐ketotestosterone on genital papilla morphology in the sex changing fish Lythrypnus dalli
Authors: Carisle S. L. , Marxer‐Miller S. K. , Canario A. V. M. , Oliveira R. F. , Carneiro L. , Grober M. S.
Published: April 2005

Five days after implantation with 11‐ketotestosterone (KT) female Lythrypnus dalli exhibited elevated urinary KT levels and male‐like genital papilla morphology. Papilla length increased, width decreased, and length : width ratio increased. Control fish exhibited increases in papilla length, and length : width ratio on day 3, but not on day 5. Changes in the total area of the papilla were not statistically significant. It is suggested that KT mediates genital papilla morphology rapidly and thus may be a useful indicator of circulating KT in L. dalli.
Infection of sardine eggs by the protistan endoparasite Ichthyodinium chabelardi off Portugal
Authors: Stratoudakis Y. , Barbosa A. , Meneses I.
Published: April 2005

In 1997 and 1999 around 30% of the stations off Portugal sampled for sardine eggs Sardina pilchardus included eggs infected with Ichthyodinium chabelardi. A randomization test on the mean nearest neighbour distances of parasitized stations did not reveal evidence of significant spatial clustering. The mean prevalence of infection was c. 0·05 for both years, but the probability of parasite detection increased considerably with egg age. Eggs in their first day of development (before the embryo is formed) were not parasitized; most parasitized eggs were in the cohorts close to hatching. Although the reasons for age‐dependent detection are unknown, if all parasitized eggs of the cohort ready to hatch were to die, infection by Ichthyodinium chabelardi would lead to mortality rates similar to those reported for the average daily mortality of sardine eggs and early larvae.
Respiratory characters of three species of haplochromine cichlids: Implications for use of wetland refugia
Authors: Rosenberger A. E. , Chapman L. J.
Published: April 2005

Respiratory characters of three east African haplochromine cichlid species that differ in their use of hypoxic wetlands were examined to consider the potential of dissolved oxygen as one factor affecting habitat use. All three species had a large gill surface area, ranging from the 67th (Pseudocrenilabrus multicolor victoriae) to 98th (Astatotilapia velifer) percentile of the known gill size range for freshwater fishes. Pseudocrenilabrus multicolor victoriae was the most tolerant to hypoxia exhibiting the lowest aquatic surface respiration (Rs)thresholds and lowest critical oxygen tension of the three species. Astatotilapia velifer had the highest ASR thresholds, gill ventilation rates, and level of surface activity of the three species, indicating a relatively low tolerance to hypoxia. Prognathochromis venator was intermediate in its response to hypoxia. These findings are discussed in light of survivorship and distribution patterns of these species following Nile perch introduction into Lake Nabugabo.
The Role of gastric evacuation rate in handling time of equal‐mass rations of different prey sizes in northern pike
Authors: Nilisson P. A. , Bröunamark C.
Published: April 2005

In a laboratory experiment, northern pike Esox lucius gastric evacuation rates did not differ between equal‐mass rations of small and large prey. In a comparison between intermediate and large prey, the pike were unable to fit two intermediate prey completely into the stomach at the same time, resulting in two consecutive evacuations, and changes in patterns of gastric evacuation. Thus, total gastric evacuation time was not affected by prey size composition in equal‐mass rations, but patterns in evacuation rate may depend on the size ratio between predator and prey. Cumulative manipulation time between strike and complete swallowing of prey differed between equal‐mass rations of small, intermediate and large prey, in that small prey took the shortest time to manipulate. Pike had problems striking and redirecting intermediate prey to swallow them head first, and the manipulation times for intermediate prey were as long as for large prey. Since an increased time manipulating prey in the mouth increases risk of predation and intraspecific interactions in pike, it is concluded that risks associated with long manipulation times, and not only energy per total handling time, determine prey value and prey size preference in this piscivore.
Corynosoma spp. may be useful biological tags for saithe in the northern North Sea
Authors: Comiskey P. , MacKenzie K.
Published: April 2005

The acanthocephalan parasites Corynosoma spp. could be useful biological tags for estimating the proportions of saithe recruiting from nursery areas in Scottish and Norwegian coastal waters to the central northern North Sea.
First record of Argulus foliaceus on the European eel in the British Isles
Authors: Evans D. W. , Matthews M. A.
Published: April 2005

In summer 1998 European eels infected with Argulus foliaceus (L.) were detected in the Erne catchment, Ireland. This is the first documented report of A. foliaceus parasitizing eels in Ireland or the U.K.
Effects of telemetry transmitters on swimming performance of adult Atlantic salmon
Authors: Thorstad E. B. , ØKland F. , Finstad B.
Published: April 2005

Swimming performance and blood physiology of adult Atlantic salmon (1021–2338 g, total body length 45–59 cm) were not affected when equipped with external (two sizes) or body‐implanted telemetry transmitters compared with untagged controls.
A new species of Encheloclarias from Sumatra
Authors: Ng H. H. , Tan H. H.
Published: April 2005

Encheloclarias velatus sp. nov. is described from central Sumatra. It diers from its congeners in having confluent anal‐ and caudal‐fin bases, number of anal‐fin rays, number of caudal vertebrae, length of anal‐fin base, body depth at anus, head length, snout length, and interorbital distance.
Sex differences in behaviour as an indirect consequence of mating system
Authors: Magurran A. E. , Garcia C. Maciás
Published: April 2005

A considerable literature has been devoted to documenting differences between the sexes. However, relatively little attention has hitherto been directed towards those differences that arise as an indirect consequence of mating system even though they can have profound implications for the daily lives of the animals involved. In this review we focus on differences in the non‐reproductive behaviour of fish and relate these to sexual dimorphism in size and morphology, and to variance in fitness between the sexes. In line with our expectation, differences in distributional ecology, schooling, aggression, predator avoidance and foraging are exaggerated in sexually dimorphic species and polygamous mating systems. Nonetheless, the behaviour of males and females may also differ in sexually monomorphic and monogamous species. We conclude by highlighting promising directions for further research.
The biology of Mustelus schmitti in southern Patagonia, Argentina
Authors: Chiaramonte G. E. , Pettovello A. D.
Published: April 2005

The relationship of body weight and total length (LT) of Mustelus schmitti in southern Patagonia was different between sexes. Changes in maturity stages in males appear at larger sizes in Ría Deseado specimens than in the Mar del Plata area. Mature females ranged from 795 to 913 mm while all male specimens >759 mm LT were mature. The data suggest that mating occurs before parturition, with simultaneous ovulation. The diet of adult M. schmitti was mainly carcinophage and the diet of young‐of‐the‐year and adults differed. The young‐of‐the‐year use the Ría Deseado as a pupping area.
Suitability of pharyngeal bone measures commonly used for reconstruction of prey fish length
Authors: Radke R. J. , Petzold T. , Wolter C.
Published: April 2005

Three measures (gape, tip and tooth row) of pharyngeal bones from 13 Eurasian cyprinid fish species caught in north‐eastern Germany were used to establish species specific bone measurelength relationships for reconstruction of prey fish length. Left and right bones were symmetrical in the case of gape, tip and length of tooth row in 69, 46 and 8%, respectively. Gape and tip showed significantly lower maximum values of relative error than the tooth row measure. A comparison of bone measures established for roach Rutilus rutilus (L.) and bream Abramis brama (L.) from north‐eastern and from southern Germany showed significant differences. Left and right bone measure‐length relationships are not generally identical. Gape and tip measures allow more accurate back‐calculation of length than tooth row measures and locality specific relationships should be established.
Modulatory effect of temperature on the influence of dietary linolenic (18 : 3 n‐3) and linoleic (18 : 2 n‐6) acids on the gonadal recrudescence in Clarias batrachus (L.)
Authors: Acharia K. , Lal B. , Singh T. P.
Published: April 2005

During the late postspawning phase, freshwater catfish Clarias batrachus fed a diet rich in linseed oil (18: 3 n‐3) (LSO) and 13L : 11D photoperiod and at 28° C showed increases in ovarian weight and plasma levels of testosterone and oestradiol‐17β, and in concentrations of free fatty acids (FFA), monoglycerides (MG), diglycerides (DG), triglycerides (TG), phospholipids (PL) and esterified cholesterol (CE) in the liver, plasma and ovary. In fish fed a diet rich in sunflower oil (18: 2 n‐6) (SFO) under the same conditions, plasma testosterone decreased sharply, concentrations of FFA, DG and TG increased in the liver and plasma and ovarian levels of TG and CE decreased. Neither diet was gonadostimulatory when fed at 18°C.
Using truss networks to estimate the biomass of Oreochromis niloticus, and to investigate shape Characteristics
Authors: Hockaday S. , Beddow T. A. , Stone M. , Hancock P. , Ross L. G.
Published: April 2005

Truss and length measurements were made on 463 tilapia Oreochromis niloticus of known mass. These measurements were then used to build mathematical models to estimate tilapia biomass. Two different approaches were used to build the models. The first was to take some simple mathematical models, and to optimize them using least squares regression. The second approach was to build models using artificial neural network software. Models were built for two different but overlapping size ranges and both approaches were successful in creating models that estimated the total biomass to within ±1%. The truss measurements were also used to assess the principal shape components of different sized tilapia.
Sibling cannibalism in dorada under experimental conditions.
Authors: Baras E. , Ndao M. , Maxi M. Y. J. , Jeandrain D. , Thomé J. P. , Vanadewalle P. , Mélard C.
Published: April 2005

Cannibalism among embryos and larvae of Brycon moorei (Characidae) occurs during daytime and night‐time, and persists under permanent darkness. Embryos and larvae of dorada provisioned with formulated feed over the first week of exogenous feeding did not survive, except for those exerting cannibalism. When oered alternative fish prey [embryos ofProchilodus magdalenae(0·5–0·8 mg) andOreochromis niloticus(9·10 mg)], 1‐day‐old embryos of dorada preferred preying on these, thereby reducing early cannibalism. However, this promoted depensatory growth and more intense cannibalism later in the larval stage. Dorada provisioned withArtemianauplii in excess showed more homogeneous growth and higher survival, most cannibalistic acts being restricted to the first 24 h of exogenous feeding, just after oral teeth were fully developed (21 h after hatching). Provisioning dorada with Artemia nauplii a few hours before their oral teeth were fully developed reduced early cannibalism from 41 to 15%. High proportions of deformed fish caused higher mortality, both directly and indirectly, as they promoted early cannibalism, depensatory growth and more intense cannibalism among larvae. The initial sorting of embryos, based on their occupation of the water column improved survival significantly during the first week of exogenous feeding, up to 52% in progenies containing <10% of deformed fish. Size‐grading of larvae and young juveniles over the next 2 weeks reduced cannibalism to 2·6 and 1·9% day−1, in the first and second weeks, respectively. These results indicate that cannibalism in dorada can be mitigated eciently through appropriate rearing procedures, and open promising perspectives for the intensive culture of this fast‐growing tropical species.
Lunar synchronization of testicular development and plasma steroid hormone profiles in the golden rabbitfish
Authors: Rahman M. S. , Takemura A. , Takano K.
Published: April 2005

Weekly changes in the gonadosomatic index (IG) of male golden rabbitfish Siganus guttatus showed two peaks corresponding with the new moons in June and July. The testes developed synchronously toward the first lunar quarter in June and July. After the second spawning, the sperm duct and the seminiferous tubules were occupied by residual spermatozoa and spermatogonia, respectively. Weekly changes of plasma testosterone, 11‐ketotestosterone and 17,20β‐dihydroxy‐4‐pregnen‐3‐one coincided with those of testicular activity. They reached their peaks 1 week before spawning coinciding with the peaks of IG and testicular development. These cyclical changes in plasma steroid hormones suggest that lunar periodicity is a major factor that synchronizes testicular activity of S. guttatus.
Diet of broadstripe cleaning gobies on a Barbadian reef
Authors: Arnal C. , Côté I. M.
Published: April 2005

Gnathiid isopod larvae constituted the majority of countable food items taken by broadstripe gobies, Elacatinus prochilos, on Barbadian coral reefs, which confirms their important role in cleaning interactions. However, E. prochilos does not rely exclusively on cleaning for food since a large amount of benthic material, mainly sponge and coral polyps, was observed in the stomach contents of all cleaners. Less than one‐third of cleaners had ingested ectoparasites. Elacatinus prochilos appears to consume few ectoparasites compared with other Elacatinus species elsewhere in the Caribbean and with Indo‐Pacific cleaner species.
Near‐surface captures of post‐juvenile anglerfish in the North‐east Atlantic—an unsolved mystery
Authors: Hislop J. R. G. , Holst J. C. , Skagen D.
Published: April 2005

Thirty four well‐grown (length range 24–103 cm) individuals of the demersal anglerfish Lophius piscatorius were captured close to the surface at widely scattered locations in the North‐east Atlantic, some over considerable depths (to 2600 m).
Microsatellite allelic heterogeneity among hatchery rainbow trout maturing in different seasons
Authors: Fishback A. G. , Danzmann R. G. , Ferguson M. M.
Published: April 2005

Allele frequencies were determined at 14 microsatellite loci in 284 female and 50 male rainbow trout that were sampled throughout the spawning season from a commercial trout farm. Phenotypic selection has expanded the spawning season of the broodstock from 2 weeks to 8 months. Females maturing in different seasons showed significantly different allelic distributions (P<0·001) at all loci. The spawning time for the majority of females sampled could be predicted based on their genotypic information [chromosome segment sharing coefficient (CSSC) values]. CSSC analyses assigned 100, 56, 76 and 68% of summer, fall, winter, and spring spawning females, respectively to the season from which their gametes were actually collected. Alternatively, only 38 and 14% of summer and spring spawning XY males respectively, were assigned to the correct season. Loci linked to thermal tolerance and spawning time quantitative trait loci (QTL) showed significantly greater heterogeneity (higher average Ds values) in allele frequencies than those not known to be linked to QTL based on previous work. Thus, phenotypic selection for spawning time has led to concomitant changes in allele frequencies at markers of QTL. This suggests that the QTL detected in our previous work have detectable effects in fish from other genetic backgrounds.
Early development of Zingel streber
Authors: Kováč V.
Published: April 2005

Zingel streber eggs contained a relatively large yolk (1·63–1·83 mm diameter after activation) and were strongly adhesive. The egg envelope was thick and not transparent. Embryos hatched very late–from 14 to 19 days after activation. Embryonic development was long (23 days at mean water temperature 14·3°C). The circulatory system appeared early, being characterized by a complex anastomosing vitelline system and by well‐developed segmental vessels. This suggests that Z. streber embryos can exploit available oxygen sources very efficiently, unlike Gymnocephalus spp. whose respiration efficiency does not increase dramatically until the first larval step. Skeletal development is also described and discussed. High investment into the quality of sexual products, relatively fast development of sense organs and swimming abilities, way of spawning, long embryonic period, short duration of two vulnerable steps, and early development of spiny structures on the head provide the embryos and larvae with relatively efficient protection against predators. On the other hand, low fecundity together with highly specialized habitat requirements make Z. streber a vulnerable species that is very sensitive to perturbations in its environment.
Male mating success in the Azorean rock‐pool blenny: the effects of body size, male behaviour and nest characteristics
Authors: Oliveira R. F. , Miranda J. A. , Carvalho N. , Gonçalves E. J. , Grober M. S. , Santos R.S
Published: April 2005

Larger male Azorean rock‐pool blenniesParablennius sanguinolentus parvicornisreceived more female visits, were courted more often by females and received more spawnings. Larger males also received a higher number of male intrusions, attacked more conspecifics and defended larger territories. Larger males showed more nest cleaning behaviour and a marginally non‐significant trend for higher egg fanning rate. Male courtship, male attack rate against conspecifics and parental behaviour were all correlated with the frequency of female spawnings received by each male even when controlling for male size, suggesting that these behaviour patterns influence male mating success. On the other hand, a positive partial correlation was found between female courtship and the frequency of female spawnings, controlling for the number of female visits, which suggests a role for female mate choice on male mating success. Finally, males nesting in chambers in the bottom of pools received more spawnings than males nesting either in crevices or under boulders. However, nest opening area was associated significantly negatively with male mating success, when controlling for male size. Thus, the present data suggest strongly that male characteristics overrule nest characteristics in determining male mating success in the Azorean rock‐pool blenny.
The use of clove oil as an anaesthetic and method for sampling intertidal rockpool fishes
Authors: Griffiths S. P.
Published: April 2005

A suitable concentration of clove oil for anaesthetizing eight common Australian intertidal fishes was 40 mg l−1. Induction and recovery times at this concentration varied markedly interspecifically, although were <3 and 5 min, respectively for all but Enneapterygius rufopileus. The number of species in clove oil samples was remarkably similar to bilge pumping samples in both small and large pools, although the number of individuals was significantly lower than bilge pumping in large pools. Number of species and individuals recorded by visual census differed from clove oil and bilge pumping methods in both large and small pools. Failure to detect all fish in pools by clove oil sampling and visual census was due to the secretive behaviour of many species and the tendency for such species as Bathygobius cocosensis not to emerge from under rocks during induction to anaesthesia. Complete draining of pools by bilge pumping, although time consuming, was a more accurate method of sampling rockpool fish assemblages than clove oil. However, clove oil is an effective stand‐alone sampling method because the number of fish and individuals are remarkably similar to samples obtained by bilge pumping. Clove oil is a favourable anaesthetic for temperate Australian intertidal fishes as mortality is extremely low, it is inexpensive and user‐safe, and induction and recovery times are short, although still sufficient to record biological information and identifications of fish whilst under anaesthesia.