bluuebunny/crossref_metadata_2025 huggingface dataset:
Behaviour and diet of sea trout post‐smolts in a Norwegian fjord system
Authors: Lyse A. A. , Stefansson S. O. , Fernö A.
Published: April 2005

In order to study the behaviour of sea troutSalmo truttaL., in the early post‐smolt phase, reared smolts were tagged with acoustic transmitters and released in the estuary of the River Aurland (Western Norway) and observed for 31–137·5 h. The study was conducted in May‐June 1991 and 1995 on a total of seven tagged smolts. The fish moved back and forth along the littoral zone close to the surface and migrated net distances of 100–8000 m. In 1991 the tagged fish were usually observed in schools averaging 24–55 fish, while the tendency to school was less pronounced in 1995. Post‐smolts of wild and reared origin were caught by 25 m long gillnets in the littoral zone. In 1991 the mean distance to shore at capture was 4·3 m and the mean depth 0·6 m, and the corresponding numbers in 1995 were 8·0 and 0·8 m. The distribution of the post‐smolts is explained by a general preference for shallow water caused by osmoregulatory problems in high‐salinity deep water, together with a preference for the sheltered littoral zone and a strong predation pressure in the open sea from fast swimming pelagic fish predators and gulls Larus sp. Schooling seemed to restrict predation by codGadus morhuaL., in the littoral zone in 1991, while no cod were observed in this habitat in 1995. In both years the stomach contents of the netted fish consisted mainly of terrestrial insects. Reared fish chose prey items similar to those taken by wild fish, but consumed less food.
Leuciscus torgalensis, and L. aradensis, two new cyprinids for Portuguese fresh waters
Authors: Coelho† M. M. , Bogutskaya N. G. , Aodrigues J. A. , Collares‐Pereira M. J.
Published: April 2005

The description of two new Portuguese freshwater fish species is presented. Leuciscus torgalensis occurs in the Mira basin and Leuciscus aradensis in the Arade basin and in two other small southern basins. The type material is deposited in the collections of the Museu Bocage, Lisbon (MB). The general external similarity between L. torgalensis and L. aradensis and two further species, L. carolitertii and L. pyrenaicus is high. The main external diagnostic character for both new taxa is the lower number of scales of the lateral line, despite the slight differences between them. Head form is a distinctive character between the two new species; such that head width is greater in L. aradensis. Distinct osteological characters between both L. torgalensis and L. aradensis and the other Iberian Leuciscus species are: the supraorbital canal and the modal vertebral formula that are shorter and lower in the new species, respectively. The preopercular–mandibular canal communication exists in L. aradensis, but not in L. torgalensis. Allozyme and mitochondrial DNA data also supported a monophyletic clade of Mira and Arade and the distinction of the two new species. The differentiation of the new species occurred either by an early isolation of the Mira and the Arade basins or by ecological conditions after the disjunction of all basins in Portugal, during the early Quaternary.
Effects of gravidity on habitat use and antipredator behaviour in three‐spined sticklebacks
Authors: Rodewald A. D. , Foster† S. A.
Published: April 2005

Habitat use was examined in six Alaskan populations of three‐spined sticklebacksGasterosteus aculeatus. In three lakes with predatory fishes, gravid female sticklebacks remained closer to refuge than did non‐gravid females, while those in lakes devoid of piscivores did not display this shift in behaviour. Gravid females in a lake with predatory rainbow troutOncorhynchus mykissused different evasive manoeuvres than did non‐gravid females duringin situencounters with a model rainbow trout. Gravid females were more likely to incorporate a protean element in their flight moffements than were non‐gravid females. Offerall, these data suggest that gravid female three‐spined sticklebacks modify habitat use and escape behaviour to reduce vulnerability to predators.
Commensalism between cichlid fishes through differential tolerance of guarding parents toward intruders
Authors: Ochi H. , Yanagisawa Y.
Published: April 2005

In the shallow waters of Lake Tanganyika, a benthic cichlidXenotilapia boulengerirests in a cluster around the nesting sites of substrate‐brooding cichlidsLepidiolamprologus attenuatusandL. elongatus. Experimental removal of parentLepidiolamprologusguarding free‐swimming young drastically reduced the number ofX. boulengeriaround these nesting sites within a few days, suggesting that their presence has a positive effect on attractingX. boulengeri.Xenotilapia boulengeriwere less frequently disturbed by the scale‐eating cichlidsPerissodus microlepisandPlecodus straeleniwhen they remained near nesting sites of these species than when stayed away. This was attributed to the territorial behaviour of guarding parents who drove away scale‐eaters at greater distances, while allowingX. boulengeri, harmless to their young, to approach the nesting site. It is concluded that a clumped distribution ofX. boulengeriresults from differential tolerance of breeding parents toward intruders that produces a safety zone from scale‐eaters.
Age, growth and cohort composition of 0+ carp in the River Murray, Australia
Authors: Vilizzi L.
Published: April 2005

The age, growth and cohort composition of young‐of‐the‐year (0+) carp, Cyprinus carpio from the River Murray in South Australia were investigated. Daily otolith microincrement formation was validated for the first 5 weeks of life in tetracycline‐marked, laboratory‐reared fish. Estimation of hatching dates from otolith microincrement counts corroborated the validation method and revealed two major peaks of spawning activity in October and in November. Two main cohorts of carp were distinguished, each consisting of several subcohorts showing variable growth rates. A simple linear regression and a logistic curve best described growth in length and weight, respectively, of wild larvae and juveniles. Two breakpoints, at 16·8 and 26·9 mm Ls, were identified in the length—weight relationship, depending on the procedure followed in fitting a piecewise regression model to the log‐transformed variables. The insertion of an additional step of development in the larva period of the early ontogeny of carp is proposed.
Aggression and growth depression in juvenile Atlantic salmon: the consequences of individual variation in standard metabolic rate
Authors: Cutts C. J. , Metcalfe N. B. , Taylor A. C.
Published: April 2005

In aquaculture, competitive interactions for food are a major source of growth rate variation, since they result in aggressive individuals acquiring a disproportionate amount of food and growing faster. Consequently, such competition increases the variance and skew of the size distribution of fish. In Atlantic salmon Salmo salar acquaculture, rearing is often initiated with juveniles of uniform size. However, the initial factors allowing fish to out‐compete others of the same size is unclear. This study shows that individual differences in standard metabolic rate (SMR) may contribute to differences in aggression between juvenile Atlantic salmon. Fish were segregated into three holding tanks on the basis of differences in relative SMR aggression was highest in the tank containing high SMR fish, and lowest in a low SMR group. However, there were no significant differences in mean growth between the three treatments, although the skew of the size distribution was much less in the low SMR group than in the high SMR group. Therefore, although mean growth was not improved in the low SMR group by excluding high SMR fish, their growth subsequently showed less variability, possibly as a consequence of fewer despotic individuals gaining disproportionate access to food.
The role of sense organs in the feeding behaviour of Chinese perch
Authors: Liang X. F. , Kiu J. K. , Huang B. Y.
Published: April 2005

Experiments were conducted to identify the roles of the individual sense organs in the feeding behaviour of Chinese perchSiniperca chuatsiby determining the consumption of natural food after selective removal or blocking of eyes, lateral lines and olfactory organs, and also by observing the behavioural response to visual, mechanical and chemical stimulation by artificial prey. Chinese perch were able to feed properly on live prey fish when either eyes or lateral lines were intact or functional, but could scarcely feed without these two senses. Chinese perch recognized its prey by vision through the perception of motion and shape, and showed a greater dependence on vision in predation when both visual and mechanical cues were available. Chemical stimulation by natural food could not elicit any feeding response in Chinese perch, and gustation was only important to the fish for the last stage of food discrimination in the oropharyngeal cavity. The sensory basis of Chinese perch in feeding is well adapted to its nocturnal stalking hunting strategy, and also explains its peculiar food habit of accepting live prey fish only and refusing dead prey fish or artificial diets.
Control of lake trout reproduction: role of lipids
Authors: Aenderson B. A. , Wong J. L.
Published: April 2005

Somatic lipid density of lake trout decreased during summer and increased after spawning in October, peaking April, prior to ovarian recrudescence. Non‐lipid density increased from June or July until August and remained relatively constant until March. All lake trout (n=30) reared on high (n=10, 0·4%), medium (n=10, 0·15%) and low (n=10, 0·05%) rations from March to September spawned. In a second experiment for which the treatments commenced in November, the proportion of females maturing in the following October (high=88%, medium=69%, low=28%) was positively related to ration levels.
Growth and food consumption of 0+ Arctic charr fed pelleted or natural food at six different temperatures
Authors: Larsson S. , Berglund I.
Published: April 2005

The effects of temperature and diet on the specific growth rate and food consumption of 1‐summer‐old Arctic charr Salvelinus alpinus were studied. Fish were reared singly in aquaria at six different constant temperatures (5, 9, 13, 16, 18 and 20°C). They were fed Neomysis integer or commercial pelleted food for 2 weeks and growth and food consumption were measured. In both experiments, growth rate increased to an optimum at 15°C. Growth rates were high in the range 13–18°C, with no significant (P >0·05) differences between temperatures. No significant (P> 0·05) differences in growth were found between fish at 9 and 20°C. There were no effects of diet on size‐adjusted growth rates. The growth efficiency decreased with increasing temperature in both treatments, but the decrease was faster in the Neomysis treatment. Charr seemed to compensate for the high water content (79·5%) of Neomysis by having a higher food intake.
A revision of the South‐east Asian catfish genusSilurichthys
Authors: Ng H. H. , Ng P. K. L.
Published: April 2005

The taxonomy of the catfish genusSilurichthysis revised, and eight species are now recognized. A neotype is designated forS. hasseltii. Two new species are described:S. gibbicepsfrom the Barito basin in southern Borneo andS. marmoratusfrom north‐western Borneo.Silurichthys leucopodusFowler, 1939, is considered a subjective junior synonym ofS. schneideriVolz, 1904. The extent of the gape and the relative positions of the dorsal and pelvic fins show considerable infraspecific variation and are of little taxonomic value. The number of anal‐fin rays is useful if used with other meristic data such as the number of vertebrae. Colour varies infraspecifically as individuals become paler and less mottled at night, but can still be used as a secondary character in separating some species. The head and caudal fin shapes are useful discriminating characters. Mature males are smaller than females and have prominent posterior serrae on the pectoral spine and articulated segments of the first pectoral‐fin element. The shape and number of these serrae are also diagnostic for some species.
Morphology of gonoducts and male genital papilla, in the bluehead wrasse: implications and correlates on the control of gamete release
Authors: Rasotto M. B. , Shapiro D. Y.
Published: April 2005

In the coral reef fish Thalassoma bifasciatum, males vary the number of sperm they release in successive spawnings with individual females in accordance with female body and clutch size. The morphology and histological structure of the male genital papilla, sperm duct, oviduct and surrounding musculature were examined in an effort to elucidate the mechanism permitting control of the number of gametes released during mating. In males, urinary and genital ducts pass separately through a common urogenital papilla and are associated with a striated sphincter muscle and a pair of thin, smooth ligament muscles arising from the first proximal anal fin radial and passing laterally around the sperm duct and oviduct. Within the papilla, the sperm duct resembles a narrow funnel whose inner walls contain longitudinal folds or septa protruding into the lumen of the duct. Dorsal to the papilla, the sperm duct enlarges and is divided into numerous, open chambers by irregular, longitudinal trabeculae. The wall of the duct and the trabeculae contain flat epithelium, smooth muscle and loose connective tissue. In females, the oviduct contains no trabeculae and is not divided into chambers. The ligament muscles are more thoroughly embedded in the sphincter muscle of the rectum than in males. Some ways in which these structures might control gamete release are suggested.
Variable length of daily feeding period in bioenergetics modelling: a test with 0‐group Baltic herring
Authors: Arrhenius F.
Published: April 2005

Including the effects of length of daily feeding period on food consumption by metamorphosed 0‐group Baltic herring in Arrhenius & Hansson's (Marine Ecology Progress Series110, 145–149; 114, 314) bioenergetics model improved its predictive accuracy, and accounted for consumption earlier in the season and lower daily consumption in autumn.
Detritivory in two Amazonian fish species
Authors: Yossa M. I. , Araujo‐Lima C. A. R. M.
Published: April 2005

In floodplain lakes of Central Amazon, the siluriform Liposarcus pardalis and the characiform Prochilodus nigricans consumed detritus with different compositions. Most of the diet of L. pardalis and P. nigricans was made of amorphous organic matter. The food ingested by L. pardalis had relatively higher organic matter (OM) (35–55%) and crude protein (10–19%) than that found in P. nigricans stomachs (10–20% and 2–5%, respectively). Both fish ingested higher quantities of OM and crude protein during the high‐water season. The differences between the two species seem to be related to their ability to select different detrital components. Striking differences were also found in the digestibility rate of OM and protein between the two species. Prochilodus nigricans assimilated only 2·3% of its intake compared with 24% in L. pardalis.
Cardiac conduction times in Sparus auratus at different heart rates. Influence of body weight
Authors: Aissaoui A. , Altimiras J. , Tort L.
Published: April 2005

At different heart rates, the conduction time through the atrium of gilthead sea bream Sparus auratus (P‐R interval) was constant in each fish but differed from one fish to another. This difference was not related to the body size of the animal, suggesting the lack of preferential conduction pathways in the atrium. A clear relation between R‐T interval and fish weight was observed, suggesting a similar conduction speed of the excitatory wave and the presence of specialized conductive tissue in the ventricle. Moreover, the P‐R and R‐T intervals did not participate in the determination of the heart rate, and all changes in the heart rate were related to changes in the T‐P interval.
The effect of temperature fluctuations on oxygen consumption and ammonia excretion of underyearling Lake Inari Arctic charr
Authors: Lyytikäinen T. , Jobling M.
Published: April 2005

Underyearling Lake Inari Arctic charr Salvelinus alpinus were acclimated to 11·0) C for 3 weeks, and then one group was maintained at 11·0) C and others were exposed to 14·4) Cconst, 17·7) Cconst or a diel fluctuating temperature of 14·3° C ± 1° C (14·3° Cfluc). Routine rates of oxygen consumption and ammonia excretion were measured over 10 days before the temperature change and over 31 days following the change. Measurements were made on fish that were feeding and growing. The temperature increase produced an immediate increase in oxygen consumption. There was then a decline over the next few days, suggesting that thermal acclimation was rapid. For groups exposed to constant temperature there was an increase in oxygen consumption (Maccl, mg kg−1 h−1) with increasing temperature (T), the relationship being approximated by an exponential model: Maccl= 46·53e0·086T. At 14·3° Cfluc oxygen consumption declined during the 3–4 days following the temperature shift, but remained higher than at 14·4° Cconst. This indicates that small temperature fluctuations have some additional influences that increase metabolic rate. Ammonia excretion rates showed diel variations. Excretion was lower at 11° Cconst than at other temperatures, and increases in temperature had a significant effect on ammonia excretion rate. Fluctuating (14·3° Cfluc) temperature did not influence ammonia excretion relative to constant temperature (14·4° Cconst).
Immunochemical detection of precursor proteins of yolk and vitelline envelope, and their annual changes in the blood of Diodon holocanthus
Authors: Fujita T. , Takemura A. , Takano K.
Published: April 2005

Two distinct groups of female‐specific proteins, vitellogenin (VTG) and vitelline envelope proteins (VEP), were detected in the blood of the porcupine fish Diodon holocanthus, and annual changes in concentration were measured immunochemically. Using antisera against yolk proteins (ab.a‐E) and VEP (ab. a‐VEP), VTG and VEP could be detected in the blood of maturing female fish and oestradiol‐17β (E2)‐treated fish. Neither protein was detected in the blood of male fish. Immunohistochemistry showed that yolk globules and the vitelline envelope enclosing developing oocytes stained with ab.a‐E. The vitelline envelope was stained specifically with ab.a‐VEP. Hepatocytes from the E2‐treated fish had immunoreactivity with both antisera. Thus, VTG and VEP appear to be synthesized in the liver by direct stimulation of E2, released into the circulation, and incorporated into respective target sites. VTG and VEP in female serum maintained high levels from April until June, suggesting that yolk accumulation, as well as vitelline envelope formation, are occurring actively during these months. Unlike VTG, small amounts of VEP were detected between December and March, suggesting that vitelline envelope formation precedes yolk accumulation and that a slightly different hormonal regulation exists in the synthesis of both proteins in the liver during the early phase of oogenesis.
Maternal influence on the size and viability of Iceland cod Gadus morhua eggs and larvae
Authors: Marteinsdottir G. , Steinarsson A.
Published: April 2005

Size, condition, and age of female‐Icelandic cod Gadus morhua were correlated to the size of their eggs and newly hatched larvae. A positive relationship was detected between egg size and some larval viability parameters, including the age at first feeding, successful development of a swimbladder, and specific growth rates during the first 15 days after hatching. These results reveal that the viability of cod larvae is related to attributes of the spawning females and that this information is important to our understanding of stock‐recruitment relationships.
Reproductive investment in the Silurus meridionalis
Authors: Xie X. , Long T. , Zhang Y. , Cao Z.
Published: April 2005

A comparison of pre‐ and postspawningSilurus meridionalisshowed that 20·7% of body stored energy was utilized during spawning for a standard male (74·5 cm) and 23·8% for a standard female (85·3 cm). About one‐third of the loss of the stored energy was released as eggs by females, and almost all of the energy loss for males and about two‐thirds for females were expended in metabolism. Stored lipid as fuel for metabolism supplied 90·0% of energy in males and 95·2% in females, and protein supplied the rest of the energy. Models for predicting energy in released gametes (Gg), deposited in the body as somatic growth (Gs), utilized in spawning activity (Sa), expended in maintenance (M, including metabolism, faeces and excretion), and food energy (C) were developed, and annual energy budgets were compiled. The balanced budget for a male aged 4 was: 100C=0·06Gg+11·17Sa+19·5Gs+69·2M, and for a female aged 5: 100C=5·48Gg+8·51Sa+15·8Gs+70·2M.
Effects on temperature on spontaneous and thyroxine‐stimulated locomotor activity of Atlantic cod
Authors: Castonguay M. , Cyr D. G.
Published: April 2005

Spontaneous locomotor activity of cod Gadus morhua maintained at 6° C tripled from February to May. In contrast, locomotor activity of cod held at 2° C was significantly lower than at 6° C (between 25 and 65% lower) and the seasonal increase was smaller. Plasma levels of both thyroxine (T4) and triiodothyronine (T3) did not differ between 2 and 6° C. T4 injection increased locomotor activity by 10% for both temperature regimes. These data indicate that low water temperature reduces locomotor activity associated with migration in cod and that thyroid hormones are not involved in this decrease. This study provides a possible mechanism through which cold waters may affects migration and distribution of cod via its Effects on locomotor activity and swimming speed.
Habitat choice in shoals of roach as a function of water temperature and feeding rate
Authors: Krause J. , Staaks G. , Mehner T.
Published: April 2005

Temperature and food availability are two important factors which affect fish growth and therefore are expected to influence habitat choice in fish. In this study, shoals of 16 juvenile roach,Rutilus rutilus, were given a choice between two chambers that differed in temperature by 1·5°C or 3°C whereas food availability was the same in both chambers (ratio 1 : 1) or higher in the colder one (ratio 4 : 1). The number of fish in each chamber was recorded for 10 min each during a pre‐feeding, feeding and post‐feeding period. Roach generally preferred the warmer over the colder chamber during the pre‐feeding periods. Temperature had a significant effect on the distribution of fish during all three time periods whereas food availability was a significant factor only during the feeding period. The important role of temperature was emphasized further by the fact that a relatively small difference in the temperature gradient of 1·5°C had a stronger effect on fish distribution than a four times higher feeding rate during the feeding period. The implications for growth rates of such short‐term decision‐making of roach are discussed.
Comparative behaviour of two species of Lepadogaster (Pisces: Gobiesocidae) living at different depths
Authors: Gonçalves D. M. , Gonçalves E. J. , Almada V. C. , Almeida S. P.
Published: April 2005

The two clingfish species studied occupied similar habitats but occurred at different depths. When compared with the subtidal species Lepadogaster candollei, the intertidal species Lepadogaster l. purpurea was less active, spent more time in shelters, visited fewer shelters, showed more site fidelity, and spent less time swimming. Feeding, swimming, and agonistic behaviours were performed mainly in close contact with the substrate in this species. It is hypothesized that these contrasts in behaviour may have evolved under different levels of turbulence.
Cold exposure increases branchial water–blood barrier thickness in the eel
Authors: Tuurala H. , Egginton S. , Soivio A.
Published: April 2005

Cold acclimation (5 v. 25° C) of freshwater eel, Anguilla anguilla induces a remodelling of gill fine structure. The increase in branchial water–blood barrier thickness may reflect an adaptive response appropriate for overwintering torpor.
Evaluation of copper, iron and lead substitution techniques in elasmobranch age determination
Authors: Gelsleichter J. , Piercy A. , Musick J. A.
Published: April 2005

Copper and lead substitution reactions were found to be useful in demonstrating growth patterns in vertebrae from several elasmobranch species. In contrast, iron substitution was ineffective in detecting variations in vertebral mineralization. The present study provides two alternative methods for elasmobranch age determination that may prove useful when traditional methods are deemed ineffective. However, species‐specific variations in the efficiency of these methods reemphasize the observation that different types of vertebrae often require different methods of staining.
Influence of spawning on swimming performance and muscle contractile properties in the short‐horn sculpin
Authors: James R. S. , Johnston I. A.
Published: April 2005

The total distance travelled during the first two kinematic stages of the escape response of short‐horn sculpin was significantly greater in post spawning fish (0·41 L) than in gravid fish (0·23 L). The maximum velocity of the snout during the C‐bend was significantly higher (5·6 L s−1) in postspawning fish than in gravid fish (3·8 L s−1). To investigate some of the mechanisms underlying changes in swimming performance, the contractile properties of fast muscle fibres were determined in fish of similar body length. The rate of tetanic force relaxation (time from last stimulus to 50% peak force) was 34% faster in gr avid than in postspawning fish. Maximum contraction velocity, determined by the slack‐test method, was significantly higher in gravid than in postspawning fish (6·8 v. 5·9 muscle lengths s−1). In contrast, both maximum isometric stress and power output (determined from the force–velocity relationship) were >50% higher in fibres from postspawning than from gravid fish, even though myofibrillar protein and water contents were similar (120 mg g−1 wet mass and 86% of body mass, respectively). The results show that swimming performance and the contractile properties of fast muscle fibres vary with the reproductive cycle in short‐horn sculpin acclimated to the same photoperiodic and temperature regime.
Spawning rhythms of common snook in Florida
Authors: Taylor R. G. , Grier H. J. , Whittington J. A.
Published: April 2005

Common snook Centropomus undecimaliswere sampled monthly from the Jupiter–Lake Worth area of Florida's Atlantic coast during 1989 and 1991 (1452 fish) and from Tampa Bay on Florida's Gulf of Mexico coast during 1988 and 1989 (2090 fish). Group‐synchronous oocyte development was demonstrated. Ovarian maturation began during March or April on both coasts. Spawning was first detected histologically in April during 1989 and 1991 on the Atlantic coast and during May in 1988 and in April in 1989 on the Gulf coast. In each year, spawning ended during October on the Atlantic coast and during September on the Gulf coast. Ovarian histological evidence suggested that individual females may spawn every 1·1–2·5 days between 1400 and about 2000 hours. Final oocyte maturation occurred independently of either tidal cycle or lunar phase, and some common snook were observed in prespawning or spawning condition on every day sampled. Spawning occurred in or near major inlets to the Atlantic Ocean and the Gulf of Mexico, in secondary passes to larger inland bays and bayous, and around nearshore islands.
Temperature and oxygen tension influence the development of muscle cellularity in embryonic rainbow trout
Authors: Matschak T. W. , Hhopcroft T. , Smason P. , Crook A. R. , Stickland N. C.
Published: April 2005

Muscle cellularity at a developmental stage around the time of hatching was examined in rainbow trout which had been reared from the eyed stage at three different temperature regimes (5, 10 and 15° C) and different O2 tensions [70% of air saturation value (ASV) at 5° C, 100% of ASV at all temperatures, and 150% of ASV at 10 and 15° C]. It was found that, as has been shown for other species, there was a difference in muscle fibre numbers and fibre cross‐sectional areas between some of the regimes. There was a decrease in fibre number at the intermediate and higher temperature, and a decrease in fibre size at the high temperature. The temperature effects observed were modified by the applied changes in O2 tension. An increased O2 tension at 10° C led to an increase in fibre size whereas a decrease in O2 tension at the low temperature resulted in a decrease in fibre number. The largest total white muscle cross‐sectional area was achieved at 10° C under high O2 conditions. Temperature and O2 tension therefore had a clear effect on muscle cellularity and there was a significant interaction between the two parameters.
Reef fish behaviour during a total solar eclipse at Pinta Island, Galápagos
Authors: Jennings S. , Bustamante R. H. , Collins K. , Mallinson J.
Published: April 2005

Diurnal fishes responded rapidly to decreased light levels during a total solar eclipse and sought shelter in the reef. Nocturnal fishes sometimes left the cover of their daytime habitats. The activity cycles of diurnal reef fishes appear to be a direct response to changes in light level.
Body size and food‐patch finding in a stickleback shoal
Authors: Peuhkuri N.
Published: April 2005

In mixed shoals of small and large three‐spined sticklebacksGasterosteus aculeatus, there were no differences between small and large fish in the probability of finding a food patch, nor in the time of their patch discovery.
Explosive speciation in cichlid fishes of the African Great Lakes: a dynamic model of adaptive radiation
Authors: Sturmbauer C.
Published: April 2005

In the African cichlid species flocks several corresponding ecotypes and species communities have evolved independently in each of the lakes. These flocks can be viewed as reiterations of a process, induced by the same type of external event (the formation of a lake) and seeded by the same group of organisms, equipped with the same innovative potential. The East African lakes differ in their ages, so that different stages of adaptive radiation of a single group of fishes can be studied simultaneously. This review combines findings on various African cichlid species flocks and derives a generalized model of cichlid adaptive radiation. The model constitutes four stages, defined by the most influential habitat characteristics and interactions among members of the species community at each phase. It is an attempt to provide an explicit hypothesis for a dynamic evolutionary process, as a basis to future studies.
Phylogenetic relationships among the mollies (Poeciliidae: Poecilia: Mollienesia group) based on mitochondrial DNA sequences
Authors: Ptacek M. B. , Breden† F.
Published: April 2005

A 505‐bp sequence from the control region (D‐loop) and the complete 1047 bp of the NADH dehydrogenase subunit 2 (ND2) gene were examined for individuals from 11 species of mollies included in the group Mollienesia. All three species of sailfin mollies of the Poecilia latipinna species complex were included (P. latipinna, P. petenensis and P. velifera); this group is named after the strikingly large dorsal fin in males. Six members of the shortfin P. mexicana complex (P. gilli, P. mexicana, P. orri, P. catemaconis, P. latipunctata and P. sulphuraria) and two members of the shortfin P. sphenops complex (P. butleri and P. sphenops) were examined. To test the monophyly of the Molliensia group, two species of mollies outside of this group were included: P. caucana and P. vivipara. The guppy P. reticulata was used as the outgroup taxon. Similar topologies were recovered using three phylogenetic methods (maximum parsimony, neighbour joining and maximum likelihood) and revealed several interesting relationships. First, all members of Mollienesia form a monophyletic group, which supports the more traditional taxonomy and classification of these species as comprising the subgenus Mollienesia as proposed previously. Second, the species of mollies outside of the Mollienesia group are only loosely allied with the Mollienesia clade; P. caucana is the sister taxon to Mollienesia, but P. vivipara lies outside of this Mollienesia‐P. caucana clade. Third, the three sailfin molly species form a monophyletic group within the Mollienesia clade, but interestingly, shortfin species are paraphyletic due to the inclusion of a single shortfin species, P. latipunctata, within this sailfin clade. The exact placement of P. latipunctata within the sailfin clade is unclear. Fourth, the remaining shortfin species form a monophyletic sister clade to the sailfins and are separated into two groups, one containing P. sphenops and P. catemaconis and a second lineage leading to the remaining shortfin species. This arrangement does not support the morphological separation of shortfins into a P. sphenops and a P. mexicana species complex. Bootstrap analyses support the monophyly of Mollienesia (78–85%), the sailfin clade (100%) and the shortfin clade (79–95%).
The role of extreme iteroparity and risk avoidance in the evolution of mating systems
Authors: Warner R. R.
Published: April 2005

How much should a female be willing to risk in any one reproductive event? Highly iteroparous females will be risk averse and very conservative in their behaviour. Such females will be expected to avoid mortality risks and seek assurance that any current reproductive activity is safe. By way of minimizing risk, these same females will not engage in mate assessment or mate searching to the same degree as less iteroparous species, if these activities involve increased risk of mortality. Using a field experiment in a highly iteroparous species (the bluehead wrasse, Thalassoma bifasciatum), it is shown that females in this species are indeed relatively risk averse. More importantly, the experiment also shows that individuals vary in their risk aversion depending on local population size, in a manner predicted from life‐history theory. Then it is reviewed how several important aspects of the mating system in this species are best interpreted as results of conservative, risk‐averse female behaviour. Finally, these ideas are generalized to suggest how basic aspects of the mating system might differ between species with many reproductive events over the lifetime (e.g. many tropical reef fishes) v. species with few reproductive opportunities (e.g. many temperate freshwater and marine fishes).
Factors regulating the height of spawning ascents in trunk fishes (Ostraciidae)
Authors: Sancho G.
Published: April 2005

This study examined the potential causes of the difference in spawning ascent height between two species of trunk fishes,Ostracion meleagris(mean height 3.3 m) andO. whitleyi(mean height 1.5 m), above a coral reef at Johnston Atoll (central Pacific). One hypothesis proposes that ascent height is influenced by the risk of predation, and predicts that species most susceptible to predation should spawn closer to the substrate. Differences in toxicity levels were analysed to assess the potential susceptibility of each species to predation:O. whitleyiwas more toxic thanO. meleagris, thus refuting the predation‐risk hypothesis. A second hypothesis proposes that spawning pairs can use long ascents to avoid disturbances by male conspecifics. During spawning, males were frequently involved in fighting episodes and high rates of male sneaking were observed inO. meleagris, but not forO. whitleyi. Thus, the larger spawning height from the substrate may be an attempt by pairs ofO. meleagristo reduce the possibility of interference by other male conspecifics, in support of the male disturbance hypothesis.
Does male‐biased predation lead to male scarcity in viviparous fish?
Authors: Garcia C. Macías , Saborío E. , Berea C.
Published: April 2005

Male predation risk due to ornaments seldom reduces female mating opportunities because males escape costs through alternative mating strategies and/or females cease to select for highly ornamented males. Males of the Amarillo fish Girardinichthys multiradiatus (Goodeidae) have large sexually selected fins that impair attack‐avoidance manoeuvres. This fish was used to seek evidence that intersexual selection for handicapping traits can result in a deficit of acceptable mating partners. Also it was examined whether, under male scarcity, females remain choosy to the point of missing mating opportunities, and that they can exert effective control over matings, which is a pre‐condition of effective female choice. It was found that snakes prey disproportionately on males, that it leads to female‐biased sex ratios, and that highly ornamented males are more scarce after predation than males with small ornaments. Females can avoid being fertilized by unattractive males, and that missing one reproductive period can lead to infertility. Thus it appears that females have promoted the exaggeration of a male trait that increases predation risk, remain choosy even when acceptable males are scarce, and pay a large cost when missing mating opportunities. A prediction from these results is that females enjoy substantial fitness benefits from mating with highly ornamented males, which override the occasional fatal costs of refusing to mate with sub–optimal males. One potential consequence of female selectivity and control over matings when males are scarce may be a reduced capability to colonize new habitats.
Spatial and temporal patterns of distribution and abundance of a tropical fish assemblage in a seasonal Sargassum bed, Cabo Frio Island, Brazil
Authors: Ornellas A. B. , Coutinho R.
Published: April 2005

The patterns of distribution and abundance of a fish community were influenced by the magnitude of the canopy of Sargassum furcatum. It is suggested that the fish community in the sublittoral of Farol Beach is structured mainly by factors related to the availability of space and habitats. Quantitative data were collected by visual census techniques, along a belt of 30X2 m in each habitat. Fish diversity was greater in S. furcatum bed and in the rocks, than in the sand where there is less structural complexity. The fish density was related to the macroalgal biomass. Correspondence analysis and cluster analysis were used to describe and compare fish assemblages in three different habitats. The association observed between the juveniles of the sparid Diplodus argenteus, the grunt Haemulon aurolineatum and the surgeonfish Acanthurus bahianus and the different habitats in the summer, and juveniles of the other species in the autumn, indicates a pattern of recruitment of the species in these periods.
Effects of anoxia on the distribution, respiratory strategies and electric signal diversity of gymnotiform fishes
Authors: Crampton W. G. R.
Published: April 2005

This paper explores the relationship between dissolved oxygen concentration and the distribution and electric signal diversity of 64 species of gymnotiforms from the Tefé region of the upper Amazon basin. Seventeen species are able to tolerate protracted periods of anoxia in inundated várzea floodplains or in terra firme swamps. The majority do so by breathing air—either with specialist accessory air‐breathing organs or via their gills. An assemblage of 38 species of gymnotiforms which are unable to tolerate hypoxia undertake lateral migrations from well‐oxygenated river channels into and out of the várzea floodplain in response to oxygen availability. These have evolved behavioural adaptations to avoid hypoxic water. While there is a mix of tone‐ and pulse‐type electric organ discharges (EODs) in species that live only in permanently well‐oxygenated habitats, 16 out of the 17 species that live in anoxic habitats have pulse‐type EODs. The tone‐type signals may have less flexible and perhaps greater overall energetic demands that impose handicaps in habitats where oxygen is a limiting factor. Many tone‐type species also have more active swimming behaviour which could impose further energetic demands.
Depauperate freshwater fish communities in Sabah: the role of barriers to movement and habitat quality
Authors: Martin‐Smith K. M. , Laird L. M.
Published: April 2005

Up to 30 species of fish were generally found in medium‐sized rainforest streams in Sabah, Malaysia. However, depauperate fish communities were found in two streams above large (>8 m) waterfalls (five and nine species) and in two very small streams located in deep forest (five and six species). A fifth stream with small cascades and waterfalls had a faunal list of 12 species. Species resident above waterfalls were predominantly herbivores while fishes in the two forest streams were from a variety of trophic groups. Abundance and biomass of fishes above waterfalls were significantly lower than all other sites. A translocation experiment was performed in one stream to distinguish between the hypotheses that fish communities above waterfalls were determined solely by colonization ability and were unsaturated with species or that they were limited by habitat quality or food. Seven species (775 individuals) were trans located into one isolated section and four species (570 individuals) into another. Species that were trans located included trophic groups that were not represented by resident species. Twelve months after translocation, only four and one trans located species were collected in the two sections, all at greatly reduced densities. After 20 months, the number of species were three and two, respectively. One trans located species, Rasbora sumatrana, had increased in abundance from 12 months and juveniles were present in the population. Individuals of other trans located species appeared to be remnants of stocked populations. Abundance and biomass of resident species fluctuated widely between years. Interpretation of results was complicated by a large flood which substantially changed habitat conditions about a month after translocations were performed. It is suggested that two different factors were responsible for depauperate communities: movement barriers for waterfall sites and physicochemical conditions and/or habitat availability at other sites.
Effects of access restrictions and stocking on small water body fisheries in Laos
Authors: Lorenzen K. , Garaway C. J. , Chamsingh B. , Warren T. J.
Published: April 2005

Four different management regimes were identified in small water bodies in Laos: open‐access fisheries, both with and without stocking of exotics (mainly Nile tilapia Oreochromis niloticus); community fisheries with restricted access and regular stocking; and fisheries rented out to corporate entities, based on indigenous stocks only. These regimes represent all possible combinations of the two management measures, access (open/restricted) and stocking of exotic species (no/yes) and a test fishing experiment assessed their effects on stock abundance, richness and diversity. The combination of access restrictions and stocking had a strong positive effect on total standing stocks. Stocks of indigenous fish were significantly increased by access restrictions, while stocking of exotics had no effect on indigenous standing stocks. Community fisheries targeted large sizes of exotic species while reducing the exploitation of smaller size groups, which accounted for much of the indigenous stocks. This suggests that stocking can promote active effort regulation and reduce the exploitation of natural stocks. Data on yields and effort were too limited to allow the use of inferential statistics, but indicated that community fisheries were exploited with much lower effort and gave lower yields than open access fisheries, while providing higher returns to fishing effort. This suggests that active management is effective in increasing standing stocks and the efficiency of exploitation, but does not necessarily increase yields unless optimal management regimes can be identified and implemented by the management institutions. No significant effects on wild stock richness or diversity were detected in the test fishing experiment, but wide confidence limits indicated a low statistical power of the test and therefore no definitive conclusions could be drawn.
An interdisciplinary evaluation of the status and health of African lake fisheries using a rapid appraisal technique
Authors: Preikshot D. , Nsiku E. , Pitcher T. , Pauly D.
Published: April 2005

Data from biological, economic, sociological, and technological attribute lists for 32 African lake fisheries were analysed with multivariate statistics. Multidimensional scaling (MDS) was used to create two‐dimensional graphic ordinations of the fisheries for each of these four attributes lists. An overall MDS ordination was also generated, based on the fisheries’ scores in the four ordinations. Groupings in each MDS ordination were achieved through cluster analysis. Multiple correlations was used to help determine the attributes which were most important in creating the MDS ordinations. This work showed that relatively fast and simple assessments of the status of African lake and other fisheries can be achieved. The technique also provided insight to help resolve the confounding information often associated with fisheries assessment. Diagnostic information may also be a product of such investigations as this research identified African lake fisheries at risk of declining standards. Indeed, many of the fisheries studied demonstrated similar interdisciplinary symptoms of fisheries decline as other small‐scale tropical fisheries.
Conservation genetics of freshwater fish
Authors: Vrijenhoek R. C.
Published: April 2005

Genetic markers have helped to resolve many difficult taxonomic problems and map patterns of diversity within and among remnant populations of threatened and endangered species. Knowledge of historical patterns of gene flow can help to manage dispersal among anthropogenically fragmented populations. Genetic considerations are used in the design of captive breeding programmes that avoid inbreeding depression and artificial selection that may impact on Darwinian fitness. Case studies from endangered populations of topminnows from North American deserts are used to illustrate a variety of methods used in conservation genetic studies. Several merits of studying putatively neutral, molecular markersv.adaptive phenotypic traits are discussed.