摘要:

Close observation of the breeding activities of specimens ofTilapia discolourobtained from Lake Bosomtwe and held captive in glass aquaria, a net cage and a pond showed that this species practises substrate‐brooding; the eggs were incubated and hatched in prepared nests. However, brief egg‐carrying tendencies were observed; both the male and female brood fish carried the eggs in their mouths from the sites of spawning to new sites. Both sexes also made and guarded the nests, incubated the eggs and provided protection to the young

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1987.tb05726.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Otoliths of southern bluefin,Thunnus maccoyii, of between 42 cm and 167 cmf.l., taken from waters off New South Wales, South Australia, and Western Australia were prepared to reveal annual banding. Methods of preparation and examination are detailed.Otolith growth was demonstrated to be directly proportional to fish growth over the size range studied. Sampling over 13 months provided validation of the annual nature of bands for fish in their 3rd, 4th and 5th year of growth. Band formation of fish in their 2nd, 6th, 7th, 8th and 9th years of growth also appeared to be annular, though samples were available from an insufficient number of months for confident validation.Von Bertalanffy growth parameters derived from determined age‐at‐length are LL, 261.3cm;k, 0.108,t0, –

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1987.tb05727.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The presence and localization of acid and alkaline phosphatase, non‐specific proteases, aminopeptidase, amylase, non‐specific esterase and lipase was investigated by histoenzymologic methods in fed and fasting turbot from day 1 to day 40 post‐hatching and compared with published data. Alkaline phosphatase and aminopeptidase activities were delected at day 1 in the distal region of the developing digestive tube. At day 3 (opening of the mouth) aminopeptidase and alkaline phosphatase activities were found all along the intestine. Sites of non‐specific esterase and protease activities became apparent in the digestive tract at days 2 and 3 respectively. Amylase was present in the exocrine pancreas at day 3 and in the lumen of the intestine at day 4. Acid phosphatase was active in the cellular structure surrounding the yolk stores and in the lipid droplets at day 1 and in the intestinal epithelium at day 3. Lipase was found at day 15 when the larvae metamorphose into juveniles.All the investigated enzymes were detected in fasting animals, except for lipase. However, the intensities of the enzymatic activities were weaker in the fasting specimens relative to the fed specimens between days 7

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1987.tb05728.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

A preliminary report is made on the distribution of acid phosphatases and acid esterases in the cells of rainbow trout. A modified technique for the cytochemical demonstration of acid esterases is given, resulting in clearer visualization. Lymphocytes undergoing transformation in the presence of phytohaemagglutinin show a parallel decrease in enzyme localization for acid esterase and acid phosphatase as transformation in culture proceeds.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1987.tb05729.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

In three different strains of brown trout a marked reduction in the number of circulating lymphocytes occurred in the blood of sexually mature male and female fish during the spawning season. This lymphocytopenia was closely correlated with elevated plasma cortisol levels in all three strains. It is well established that sexual maturation in salmonid fish is associated with an increase in susceptibility to disease: the present study provides strong evidence that this is mediated, at least in part, by a cortisol‐induced suppression of lymphoid activity. These findings are discussed in relation to possible physiological roles of cortisol during the spawning period and to the evolution of semelparity in salmonid fis

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1987.tb05730.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The incidence of sexual inversion inPhoxinus phoxinushas been studied by examining histologically (a) the gonads of 406 adult specimens caught from the wild during a period of 16 months, (b) the gonads of 168 adults kept in captivity in groups with an experimentally altered sex‐ratio, and (c) the differentiation of the gonads in the fry.All the adults had either testes or ovaries and no case of intersexuality was observed. For both testis and ovary, we recognized two phases, depending on the seasonal cycle: an active spring‐summer phase, corresponding with the period of reproduction, and a quiescent autumn‐winter phase. The ovaries showed an asynchrony in oocyte development, which is typical of species that spawn many times during the breeding season.InP. phoxinusthe ovaries are easily recognizable just one month after hatching and testes are well differentiated in 2‐month‐old fingerlings. Differentiation is, therefore, precocious and follows a pattern typical of gonochoristic species in which hermaphroditism nev

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1987.tb05731.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

A comparative study has been made of haematological parameters (erythrocyte numbers, leucocyte numbers, haematocrit and haemoglobin), erythrocyte indices (MCV, MCH and MCHC) and cytometric measurements (cell and nucleus) of 10 species of marine fish from the Visakhapatnam Coast, of which six are from harbour waters, three from rock pools and one from inshore waters. It is found that active fish have high values of erythrocyte numbers, haematocrit, haemoglobin and nucleo/cytoplasmic ratio and low values of leucocyte numbers and erythrocyte cytosome measurements. The most active of all is the inshore speciesRastrelliger kanagurtadepicting the haematological requirements of an active fish with high oxygen demand to meet the requirements of high metabolic rate. The other active fish such asMegalops cyprinoidesandMugil cephalusare intermediate, with the rock pool fish andCaranx caranguswith low values of nucleo/cytoplasmic ratio at the other extreme.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1987.tb05732.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Growth, size composition, condition factor and gonad index of the oil sardine,Sardinella longicepsVal., oscillated over an annual cycle in relation to upwelling. Growth in length was modelled using the formula of Pauly&Gaschütz (1979):whereLt= length cm at agetyears, L∞= 23.8cm, K=0.97, to=0.70, C=1.08 and ts=−0.08. The relationship of growth rate, spawning, and condition factor, to upwelling and plankton blooms is discu

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1987.tb05733.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

A new species of electric catfish,Malapterurus minjiriya, from Kainji, Nigeria, is described and a key for separating it from the two other known species is given. Notes on some aspects of the biology of the electric catfishes in Lake Kainji, Nigeria are included.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1987.tb05734.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

This study describes feeding rhythms in juvenile sole (0‐ and I‐groups) and differences in choice of prey according to age and feeding time. In the same biotype, 0‐group fish select amphipods or young opisthobranchs, whereas I‐group fish eat chiefly polychaetes such asPectinaria koreni. The daily food consumption for juvenile soles in the field (T = 19.8°C) is estimated at 7% body dry weight in 0‐group and probably less in I‐group. When compared with estimates from previous methods or models, these rations are intermediate between estimates from Kuipers' method, with a gastric evacuation rate (R) per hour representing three times the amount of food in the stomach, and those from Elliott&Persson's model withRvalue

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1987.tb05735.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY