摘要:

To overcome the problems usually met as a consequence of small numbers of fish collected for trout stock size evaluation in small rivers, a selectivity function was developed and tested in two small rivers in western Switzerland. The function takes the form InE=bL−kwhereEis the fishing efficiency,Lis the fish length in cm, k is a constant andbis the slope, estimated by regression analysis.A good fit was obtained for k = 1 (R. Flon de Carrouge) and k = 2 (R. Cerjaule). Individual selectivity functions have to be computed for each survey, because they depend on the operators of the fishing gear and on the physical and biological conditions in the rivers.The results are discussed in the light of the Petersen mark‐recapture method and the De Lury removal method for stock evaluation. The mark‐recapture method gives better results when time intervals between successive fish removals are

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb02697.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Changes in reproductive condition in the New Zealand snapperPagrus auratus(Bloch&Schneider) were monitored in a wild population over three successive years. Recrudescence occurred in spring with spawning beginning in October and continuing for 3 to 5 months. The initiation of spawning varied by up to 3 weeks and was associated with sea surface temperatures of 15–16° C. Theconclusion of spawning was associated with temperatures of 19–21° C but showed greater interannual variation than the onset of spawning. Changes in the gonadosomatic index were accompanied by parallel changes in hepatosomatic index in females but not males, reflecting the role of the liver in vitellogenesis in fe

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb02698.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The prevalence ofGyrodactylus sulurisMalmberg. 1957 on both yearlings and older parr of Atlantic salmon (Sulmo sulurL.) in the River Batnfjordselva was 100% through most of the year. With one exception, uninfested fish were only found in the winter and spring after the water temperature had fallen to almost 0° C for 2–3 months. In general, the abundance (i.e. the mean number of parasites per investigated fish) ofG. salarisincreased during the warm period of the year (summer and early autumn). Abundanceas high as 1153 and 4418 in early autumn was found on yearlings and older parr, respectively. The abundance decreased during the cold period of the year (winter and early spring), in some cases to as low as two and fourG. salarison yearlings and older parr, respectively. About 86% of theG. salarisspecimens were found on the fins of the salmon parr: mainly on the dorsal fin (34.4%) and the pectoral fins (27.0%). The remainder of the parasites were distributed on the body (7.8%), the head (3.5%), and the gills (2.6

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb02699.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The cellular composition of the blood, anterior kidney, spleen and thymus of turbotScophrhalmus maximusL., aged 1 + was determined. Ninety‐four per cent of blood cells belonged to the erythrocyte lineage of which 82% were mature erythrocytes. The leucocytes, which represented 4.5% of the blood cells, were mainly lymphocytes (50%). The presence of crythroblasts in the anterior kidney and the spleen demonstrated an erythropoietic activity in both organs. However, this activity appeared to be prevalent in the spleen which also appeared to act as a storage zone for erythrocytes and as the centre point for thrombopoiesis. Although 96% of the anterior kidney cells were leucocytes, the number of white cells per gram of organ was higher in the splee

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb02700.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Larvae ofRutilus rutilus(L.) weighing approx. 40 mg were exercised for 5 min by mechanical stimulation. Individual larvae were taken before and immediately after stimulation, and during 2 h of recovery. The concentrations of glucose, glucose‐6‐phosphate, pyruvate, lactate, 2‐oxoglutarate, and ascorbic acid were determined in individual larvae. The larvae recovered faster from forced activity than juvenile roach, recovery being complete after 1 h. Larvae also differed from juveniles in that metabolite levels increased less during activity. It is suggested that the combination of low glycolytic, and high oxidative capacity was responsible for the specific metabolic responses of the l

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb02701.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Two species of coastal flatfish (brill and turbot, Scophthalmidae) were analysed electrophoretically at 17 common enzymatic loci in samples taken from 11 sites representing the species ranges in Europe. Brill showed a mean heterozygosity (H) of 0·11 while that of turbot was 0·02. The virtual absence of genetic diversity in turbot is probably due to a very low evolutionary rate, and provides little evidence for population substructure even if various signs indicate the possibility of a hidden differentiation (presence of the taxonmaoeticain the Black Sea and differentiation of a species‐specific cestode parasite on either side of the Strait of Gibraltar). On the other hand, the weak geographic structure in brill seems to result from rapid recolonization following the last ice

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb02702.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The detection of threshold concentrations and relative stimulatory effectiveness (RSE) for 19 amino acids were studied by olfactory bulbar electroencephalogram (EEG) in the algivorous rabbitfish. The threshold concentrations for 19 amino acids ranged from 10−10to 10−5M.l‐Alanine was the most effective amino acid, and the threshold concentration was estimated to be from 10−10to 10−9M. These results were compared with the olfactory response in herbivorous and carnivorous fishes previously reported. The comparison of RSE for rabbitfish with those for other fishes showed correlation coefficients ranging fromr= 0.97 tor= 0.50, but high similarities did not correspond with difference in feeding habits for herbivores and carnivores. The role of amino acids in fish chemosensory behaviour and the olfactory response of the rabbitfish was compared with the gustatory response reported previously. It was found thatl‐serine was the most potent stimulant in both chemoreceptors,l‐proline andl‐glutaminic acid were the most potent gustatory stimulants, andl‐alanine,l‐glutamine,l‐arginine andl‐lysine were the most pote

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb02703.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Otoliths of juvenileGirella elevata(M.) were examined to obtain information about the environmental conditions experienced during early life. Patterns of increment deposition and elemental ratios in otoliths were compared in wild fish. A tetracycline experiment indicated that increments were deposited daily in juveniles. Although different patterns in the spacing of increments were found among juveniles collected at different locations and times, the widest increments were always found in the first 40 increments. Strontium: calcium (Sr: Ca) ratios increased with age in the otoliths of most wildG. elevata.The patterns of increment width and Sr: Ca ratios were not related and, therefore, were probably not under the same relative control by environmental or physiological factors. Although the number of increments can be used to age juvenileG. elevata, the utility of increment widths and Sr: Ca ratios as environmental predictors in this species is questionable without experimental validation.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb02704.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Laboratory experiments on larval white seabass,Atractoscion nobilis, showed that first feeding success on mixed zooplankton was zero, and less than 5% onArtemia nauplii, for larvae of different sizes. Experience increased success from 20% after 2 days to 69% after 14 days when larvae fed onArtemia nauplii, and to 42% after 4 days of feeding on zooplankton. This increase was attributed to learning in larvae less than 5·0 mms.l., and in part to size‐related factors in larvae greater than 5·0 mm

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb02705.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The otoliths of the scaridScarus schlegeli(Bleeker) from the Lizard Island on the northern Great Barrier Reef showed a series of clear periodic bands. The rate at which bands are deposited on the otoliths was distinguished by mark‐recapture experiments using tetracycline and marginal increment analysis. Mark‐recapture experiments were carried out both in the field and in a large aquarium system. One otolith band was deposited during the liberty periods of July 1990 to April and September 1991 while two similar bands were formed from November 1989 to February 1991. The marginal increment analysis indicated that annual bands were formed around the austral summer. Scales also displayed regular period check marks. These provided relatively reliable aging estimates for the younger fishes up to 5 ye

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb02706.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY