摘要:

Larval golden perch,Macquaria ambigua, and silver perch,Bidyanus bidyanus, were exposed to light gradients in wavebands centred on 400, 496, 601 and 695 nm at nominal quantum irradiance values of 0–1, 1–0 and 10 μmol m−2s−l. Silver perch larvae displayed stronger phototactic behaviour than golden perch, and both species were most responsive to light in the 601 nm waveband. The intensity of phototactic responses in both species was greater at higher irradiance levels. Enhanced responsiveness to longer wavelengths reflects possible adaptations to life in turbid habitats where the underwater light field is dominated by yellow/orange wavebands.At night, traps fitted with 12 h yellow lightsticks attracted more golden perch larvae than traps with blue, green, orange, red or no lightstick. The efficacy of yellow lightsticks may be due to yellow/orange wavebands not being attenuated under water as rapidly as blue or red wavebands. Yellow lightsticks also emit a greater intensity of light over a longer time than other colours tested, which may have increased the effectiveness of yellow traps. Light traps were ineffective during

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1994.tb01252.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Data are presented on the food and gonadosomatic index ofPomatoschistus minutusobtained from the bycatch of a commercial shrimp trawler.P. minutushas a diverse diet including zooplankton and hyperbenthos but mainly epibenthic and benthic animals. During the spawning season males consumed high numbers ofPomatoschistuseggs, presumably after aggressive take–overs of territories. The food ofP. minutusis compared to the food ofP. lozanoiof the same size classes obtained from the same hauls. In the absence of data on predator and prey abundance the discussion on possible interference competition between the two species remains largely speculativ

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1994.tb01253.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The distribution of three main lateral plate morphs of the three–spined stickleback,Gasterosteus aculeatus, in the Polish zone of the Baltic Sea and inland waters is surveyed. Most sites are characterized by predominance of the completely plated morph, although it is only in the Vistula River drainage basin where monomorphic complete populations prevail. Polymorphic populations with a high proportion of the non–complete morphs are found in Puck Bay (the Baltic) and in south–west Poland, Possible causes of this pattern are disc

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1994.tb01254.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Atlantic salmon (Salmo salar) raised under production conditions were sampled periodically during their life cycle, in fresh and salt water, to determine their proximate and elemental composition. The parameters changed in relation to life cycle stage and fish size, and were influenced by whether the fish were in salt or freshwater. Measurements presented can be used to assist in the formulation of feeds, and to determine the health and nutritional status of commercially reared Atlantic salmon.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1994.tb01255.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

A new species of pelagic haplochromine cichlid of the genusDiplotaxodonis described from Lake Malawi, Africa. The species, which attains a size of 14cm s. L., feeds mainly on zooplankton, shows no sexual dimorphism in size or body proportions, breeds throughout the year and lives at depths of 20 to at least 120 m. Approximately 600 tonnes of the species were caught by trawlers in 1990–1991, in the south–eastern arm of the lake alone. It appears that this species is a major component of the pelagic community, and occupies an ecological role similar to that of the clupeidLimnothrissa miodonin Lake Tangany

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1994.tb01256.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Examination of the alimentary canal of specimens of the genusEvermannellaof the form previously referred to the circumglobal speciesE. indicaBrauer, 1906 has revealed differences between specimens from the Atlantic Ocean and those caught in the Indian and Pacific Oceans. On the basis of gut morphology and skin pigmentation the Atlantic speciesE. melanodermaParr, 1928 is distinguished from the Indo–PacificE. indica. Some observations are presented on the size structure of theE. melanodermapopulation off Madeir

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1994.tb01257.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Prey exploitation was documented forHippoglossoides platessoides, Pleuronectes ferrugineus, andP. americanuscollected from southeast Sable Island Bank in February and June 1989. Diets varied significantly by sample and with fish species and length. Of 239 species consumed by flatfishes, 66 were determined to be principal prey. Crustaceans, particularly amphipods, were the most frequently exploited prey of all three flatfish species. SmallH. platessoidesfed on suprabenthic fauna, while larger fish exploited epifauna and hyperiid suprafauna.P. ferrugineusexploited epibenthic fauna, consuming crustaceans and tunicates when small and polychaetes when larger.P. americanuspreyed on epifauna; smaller fish exploited polychaetes while larger fish usually consumed crustaceans associated with ectoproct colonies. Feeding intensity was dramatically lower in February, food being found in stomachs of only 36% of H.platessoidesand 49% ofP. ferrugineus, and lacking in the stomachs ofP. americanus. In June, stomachs of 86% ofH. platessoides, 94% ofP. ferrugineusand 96% ofP. americanuscontained food. Results indicate that prey resources for the three flatfish species are partitioned by specific habitat and prey type preferences.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1994.tb01258.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Reference values for common haematological and biochemical tests were established for 64 captive Australian snapper,Pagrus auratus(Bloch&Schneider). Fish were bled from caudal vertebral sinuses after benzocaine anaesthesia. Haematological results were extremely variable for total leucocytes and types of leucocytes. There was no correlation between leucocyte counts and teucocrit values (R2=0·37). Thrombocytes were not determined by direct cell counting due to problem of aggregation. Polychromasia was common but did not correlate with reticulocyte counts (R2=0·08). Biochemical results were extremely variable for creatine kinase and aspartate transaminase but this was considered a direct result of muscle damage during collectio

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1994.tb01259.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

When treated with detergent club cells showed degenerative changes and released their contents to plug the intercellular spaces. This mechanism could act as an efficient protective barrier substantiating the role of club cells in assisting fish to overcome adverse conditions. A general decrease in the dimensions of club cells was associated with discharge of their contents. The appearance of juvenile club cells reflected their differentiation in response to increased demands to meet the challenge. Increases in the number of club cells indicated the differentiation of these cells at a rate faster than their degeneration. Localization of glycogen in club cells at the start of detergent treatment and, in general, its absence later and, in both control and juvenile club cells, is discussed in relation to the metabolic status of the cells. No marked shift was observed in the mucopolysaccharide and protein moieties of club cells.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1994.tb01260.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Spatial and temporal patterns of redd construction by Sakhalin taimen,Hucho perryi, were studied in small streams on northern Hokkaido, Japan. Spawning took place in late April with close relation to discharge patterns. Observed redd size (mean ± 95% C.I.) was 145 ± 11·8 cm in length and 84 ± 5·8 cm in width. The number of egg pockets per redd was either one or two, which is fewer than that of other salmonids reported in the literature. Spawning ground distributions in 1991 and 1992 were similar to each other in terms of the distribution mean and dispersion of the redds. Unlike other salmonids Sakhalin taimen probably constructed multiple redds during one spawning se

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1994.tb01261.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY