摘要:

The breeding biology ofOligolepis acutipennis(C.&V.), a gobiid fish abundant in the estuaries and brackish water tracts of the south‐west coast of India was studied. Data on the intra‐ovarian development of ova, the breeding season, spawning frequency, size at first maturity and sex‐ratio were based on observations for 1 year. The size distribution of ova showed no significant variation between different regions of the ovary. The gonads were classified into five maturity stages. The sequence of development of ova to maturity indicated two batches of ova developed in a single ovary in a year. The minimum size at first maturity of females was less than that of males. Seasonal variation in gonad weight and the percentage occurrence of various maturity stages of gonads showed that the fish has a protracted breeding period in which two seasons can be recognized. The females dominate over males in numbers except in the non‐breeding

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1983.tb02941.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Peaks in the emigratory activity of sexually immature, juvenile Atlantic salmon,Salmo salar, occur in autumn and early winter and in spring at the Girnock Burn in Aberdeenshire. Stream temperature is apparently without effect on the release of potentially emigrant fish from the stream. Migrants tend to leave the stream when stream discharge rate is elevated. Whereas downstream movements in autumn and the earlier part of the spring are made almost invariably when the stream's discharge rate is higher than the seasonal norm, later in spring they often occur when discharge rates are lower than the seasonal norm and when no apparent increase in absolute stream discharge rate has occurred. Emigration is depressed in the lunar quarter centred on the full moon. The nature of the relationship between the autumn and spring emigrations is discussed.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1983.tb02942.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

The development and growth of Japanese anchovy larvae,Engraulis japonica, are described from laboratory‐reared specimens. Fertilized eggs were collected from cultured parental fish. Rotifers,Anemiaand copepods were offered to larvae of different sizes. Fin ray formation was completed at 21 mm S.L. Pigmentation during development is described. Newly hatched larvae grew to 29·38 mm standard length in 62 days. The daily length increment averaged 0·43

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1983.tb02943.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Protein, lipid, water and caloric contents of immature rainbow trout, relative to size of whole fish, growing at different rates were examined by use of allometric analysis (y = axb, Huxley, 1932). Fish grew at different rates as a result of differences in ration size (satiation, or 4–5% of dry body weight), temperature (7 and 12°C) and bGH (bovine growth hormone) administration. In fingerlings, protein, lipid and caloric contents tended to increase (v. body weight) as a percentage of body composition, whereas above fingerling size, protein decreased while lipid and caloric contents still increased. These trends occurred regardless of growth rate differences. The correlations between protein, lipid, caloric contents and body weight were high so reliable estimates of body components can be made from body weight for all experimental treatments. At satiation rations (7 and 12°C), there were no significant differences in protein content, but lipid and caloric contents were significantly higher in control fish. At low rations, protein and caloric contents were lower than those at satiation rations and lipid was lower than in the control group. On a dry weight basis, in uninjected fish at 12°C, ration size did not influence the percentage composition (protein and lipid) but the low ration group had lower energy values per unit of body dry weight. At low temperature (7°C satiation), fish had lower lipid and higher protein content (dry weight basis) than their controls (12°C satiation), thereby resembling bGH injected fish at satiation rations. Values of caloric content estimated from protein and lipid values by use of standard conversion factors differed sufficiently from caloric values directly determined by bomb calorimetry to suggest that caloric values of lipids may change during growth. The increase in body caloric content during growth apparently results mainly from an increase in the percentage of lipid. The similarity of body composition between different growth rate groups implied a tendency for conservation of relative proportions of components such that body composition can be approximated from body weight. Equations were also given to describe the relationship between water content and body constituents, and the relationship between condition factor (K) and both the body dry weight and lipid c

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1983.tb02944.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

The digestibility of the aquatic macrophyteHydrilla verticellataby the Asian cichlid,Etroplus suratensiswas estimated using three indigenous markers viz. hydrolysis resistant organic matter (HROM), crude fibre (CF) and hydrolysis resistant ash (HRA). In the fodder HROM showed the least variation and HRA the highest. The recovery of HRA in the faeces was always higher than 100% whereas HROM was the nearest to 100%. The total digestibility varied between 34·6% and 51·9%, and the digestibility estimates were higher when HRA was considered as the marker. The overall protein and lipid digestibility varied between 59·2%–70·9% and 65·0%–70·1 % respectively. It is suggested that HROM is a better reference marker in comparison CF and HRA. Daily variation in protein digestibility ranged from 51·2

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1983.tb02945.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

A number of the techniques commonly employed in fish growth and nutrition studies are evaluated and limitations imposed by their use are indicated. Total and digestible energy values of dietary formulations should be measured directly and the use of caloric conversion coefficients and assumed digestibility values may lead to serious error. There is considerable misunderstanding relating to the term metabolizable energy and metabolizable energy has been estimated in a number of ways, all of which are unreliable. In view of this, it is suggested that there is a good case to be made for ceasing to use the term.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1983.tb02946.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

GoldfishCarassius auratusL., were held for 1 month on one of four different photoperiods. In those groups with diel variations of serum cortisol and thyroxine (approximately 60%) the variations were entrained to the photoperiod; peak titres occurred around light onset, minimum titres at light offset. Fish held on two of the photoperiod regimes had diel variations in serum protein, however, the pattern was not consistent in relation to any aspect of the photoperiod.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1983.tb02947.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

The sensitivity of the leucocrit as a stress tolerance and fish health assessment method was evaluated by subjecting juvenile coho salmon,Oncorhynchus kisutch, or steelhead trout,Salmo gairdneri, to standardized crowding, handling, temperature and disease challenges. The leucocrit was a sensitive indicator of the physiological stress resulting from crowding at population densities of 0·2–0·4 kg l−1, and to the stress of handling and to temperature changes. It was relatively insensitive to physiological sampling procedures which supports its continued development as a stress assessment method.In the case of fish diseases, subclinical or activeRenibacterium salmoninarumandYersinia ruckeriinfections had essentially no effect on leucocrit values. In contrast, activeAeromonas salmonicidainfections significantly depressed the leucocrit. However, no change was seen during the subclinical (incubation) phase prior to the development of an epizootic. Thus, the potential of the leucocrit as a fish health assessment method appears li

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1983.tb02948.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

The concentrations of phosphorylcreatine (PCr), adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP), inorganic phosphate (Pi), pyruvate and lactate were determined in freeze‐clamped fast muscle samples fromOreochromis alcalicus grahamia fish adapted to extreme alkalinity (∼ pH 10·0) and high temperatures (Lake Magadi, Kenya). Specimens were analysed from both geothermally heated hotsprings (35–37°C) and from isolated cool pools (28°C) and from stocks acclimated to 20°C in the laboratory. The ratios of (ATP)/(ADP) and (ATP)/(ADP) (Pi) decreased with increasing body temperature consistent with an increase in glycolysis and tissue respiration rates, respectively. The apparent equilibrium constant of creatine kinase (KCK), (creatine) (ATP)/(phosphorylcreatine) (ADP) was found to decrease with increasing temperature: 20·2 (20°C), 13·9 (28°C), 8·0 (37°C). A near constant muscle and blood pH (or slight increase in alkalinity with higher temperatures) was found regardless of body temperature (Blood pH 7·64, 7·74, muscle pH 7·27, 7·51 at 20°C and 35°C, respectively). These results are consistent with an unusual pattern of acid‐base reg

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1983.tb02949.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Stomach contents of the lesser spotted dogfish,Scyliorhinus canicula, from Isle of Man waters were investigated. Dogfish fed opportunistically on a wide range of macrobenthic fauna with hermit crabs, cockles and whelks the dominant prey. Items of secondary importance included various crabs, callianassid shrimps, bivalve molluscs, holothurians, polychaetes and, when locally abundant, herring,Clupea harengus. Dogfish predated more heavily on molluscs than reported in previous studies, reflecting the abundance of molluscs in the associated benthic community.Composition of the diet altered gradually with dogfish size, reliance on small crustaceans declined and consumption of hermit crabs and molluscs increased with growth. Seasonal changes in the composition of the diet were observed. Feeding intensity was greatest during summer, related in part to increased prey availability, and was least during autumn.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1983.tb02950.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY