摘要:

TurbotScophthalmus maximuswere cannulated via the afferent branchial artery and were either net‐confined in sea water or in air for 9 min to monitor the stress response of a hatchery‐reared marine flatfish. No mortality was observed. Aerial exposure appeared to mobilize plasma free fatty acids and stimulate the interrenal tissue but had no effect on circulating glucose or lactate levels. This pattern was qualitatively similar to that induced by net‐confinement in sea water, although the magnitude and duration of the changes were more marked in the turbot handled in sea water. Aerial exposure had no effect on plasma osmolality, protein, or Cl−concentrations and only a minor effect on plasma Na+concentrations, which was in sharp contrast to the ionoregulatory disturbance noted in turbot which were net‐confined in sea water. However, plasma K+and cortisol concentrations were similarly elevated by both handling procedures. The results from these experiments suggest that whilst similarities with the salmonid physiological stress response are apparent, the lack of a plasma glucose response may represent a fundamental difference in turbot stress p

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1996.tb01110.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The utility of Sr/Ca ratios in otoliths as indicators of thermal history in fish was investigated for juvenileGirella elevata. There was no direct relationship between ratios of Sr/Ca and temperature of the water, as has been assumed in many previous studies. Sr/Ca ratios did not decrease when water temperature was elevated from 19 to 28° C. Elevation of ambient Sr levels in the sea water caused a significant increase in Sr/Ca ratios in otoliths, and there was a detectable increase in Sr/Ca ratios in otoliths of some individuals fed an Sr‐enriched diet. Multiple factors may influence natural Sr/Ca ratios in otoliths of juvenileG. elevataand their interactions make it difficult to interpret the chronology of conditions experienced by an individual fish during early life in the pelagic or benthic environme

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1996.tb01111.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The histology and mucus histochemistry of the pleuronectid post‐gastric alimentary canal was examined using light and electron microscopy. Distinct differences in goblet cell mucus histochemistry were observed between species, with the two closest taxonomic species, the winter flounder and the yellowtail flounder showing the most diversity and the halibut showing regional variation. Numbers of goblet cells within post‐gastric regions did not differ significantly between species, but were significantly different between regions within species increasing toward the rectum. The post‐gastric region was divisible into two areas based upon the ultrastructural features of lipid digestion and absorption in the intestine and pyloric caeca, and of exogenous protein in the rectum. The combination of species‐specific histochemical differences in mucus and general histological and ultrastructural differences within the post‐gastric regions between these species suggest a correlation between lumenal environmental conditions/histology and natural prey p

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1996.tb01112.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Larvae of spring spawning Clyde herringClupea harengusL. were reared at 5 and 12° C. Metabolism following burst swimming was studied in 7‐day‐old larvae at their respective rearing temperatures. Escape responses were repeatedly elicited using tactile stimulation for a period of 3 min. Larval herring were hard to fatigue and still responded to tactile stimuli after 3 min. Whole larvae were freeze‐quenched in liquid nitrogen, either immediately after exercise, or after periods of recovery of up to 24 h. Samples were freeze‐dried and analysed for whole body creatine (Cr), phosphocreatine (PCr), ATP, ADP, AMP, lactate, glucose, and glycogen using high performance liquid chromatography and enzymatic methods. The exercise regime resulted in a marked decrease in PCr, ATP and glycogen concentrations and an increase in creatine, glucose and lactate concentrations whereas there was no significant change in either AMP or ADP concentrations. The extent of phosphagen hydrolysis (approx. 110 to 15μmol PCr g−1dry body mass) and lactate accumulation (approx. 7 to 40 μmol lactate g−1dry body mass) over the exercise period was similar at the two temperatures, consistent with a relatively constant degree of effort. The rates of recovery of PCr and ATP were essentially the same at 5 and 12° C; returning to resting levels after approximately 30 min. Lactate and glycogen concentrations were restored 60 min after exercise at both temperatures. Maximum lactate clearance rates (1.2 μmol min−1g−1wet muscle mass) were an order of magnitude faster than reported for adult fi

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1996.tb01113.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

In the brackish water of the Baltic Sea successful spawning of Baltic codGadus morhuais restricted to the Bornholm, Gdansk and Gotland basins below the halocline, occurring at 50–80 m depth. Due to irregular mixing of the deep water, stagnant conditions occur regularly accompanied with unfavourable oxygen conditions. In avoiding stressful oxygen conditions maintenance of egg buoyancy is considered a major limiting factor for successful spawning of Baltic cod. Batches of eggs were incubated experimentally in a density gradient column. Egg specific gravity changed during development, decreasing from the time of gastrulation, then increasing prior to hatching. The changes in specific gravity varied among egg batches from different females and were related to egg quality, egg size and ambient salinity. Eggs achieve different specific gravity depending on incubation salinity. Initial egg specific gravity together with the ability of eggs to gain and maintain buoyancy up to hatching, determine larval specific gravity and the depth where hatching will occur, and thus opportunities for larval survival, avoiding stressful oxygen conditions and developing at favourable feeding condition

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1996.tb01114.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

A non‐contact bioelectronic monitoring system was used to record changes in heart rate, ventilation rate and swimming activity in brown troutSalmo truttaand roachRutilus rutilus, following exposure to two species of cercariae of digenean trematodes:Diplostomum pseudospathaceumwhich is a common parasite in the lens of fishes and xiphidiocercariae ofPlagiorchis elegans, a parasite of anatid birds, both of which have the snailLymnaea stagnalisas their first intermediate host. Swimming activity increased significantly in roach exposed toDiplostomumcercariae at densities as low as 3.8l−1and remained elevated for 24–36 h post exposure. Brown trout showed no response when exposed to low densities ofDiplostomum(2.9 and 5.7 cercariae 1−1) but there was a significant response at higher cercarial exposure densities (>501−1). Total activity of brown trout increased immediately, peaking after 2 h and returning to pre‐exposure levels within 5–6 h. There was a simultaneous increase in heart and ventilation rates which both declined following the reduction in activity of the fish. Heart rate then increased for a second time to a maximum level at 14–16 h and thereafter declined to reach a steady state at 3 days post‐exposure. During this period there was no significant change in total activity. The qualitative nature of the heart response was identical in five infected brown trout although the magnitude of the response varied widely among fish. Exposure to cercariae ofP. eleganselicited no response in either fish species. (c) 1996 The Fisheries Society of

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1996.tb01115.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The effects of stocking density on the demand feeding behaviour of Arctic charrSalvelinus alpinusand rainbow troutOncorhynchus mykisswere evaluated using demand feeders in combination with a monitoring system based on automatic passive integrated transponders. The proportion of total bites accounted for by top‐ranked charr and trout decreased from 87 to 15% and from 66 to 15%, respectively, when moving from the lowest to the highest densities, indicating that the ability of the highest‐ranked fish to monopolize the demand feeders was reduced at high densities. However, when the individuals were grouped into quartiles, based on their individual rank, both charr and trout ranked within the upper quartile accounted for the majority of bites independent of stocking density (87 and 72% of the total, respectively). Instead of there being a single dominant individual, as was the case under low density conditions, a small group of individuals dominated the actuation of the trigger at high densities. The two species responded differently to crowding, with the total daily bite activity of charr increasing linearly with increasing density, whereas the corresponding relationship was quadratic for rainbow trout, with a peak value at 24 to 36kg

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1996.tb01116.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Multivariate examination of partial warps allowed the description of shape differences characterizing each of 10 populationsof Mugil cephalus. Patterns of morphometric distances (overall, uniform and non‐uniform) among samples suggested that morphometry in part reflected the geographic origin of the samples. However, comparisons with allozymes and mtDNA provided no exhaustive evidence for a pure phylogenetic cause for the observed patterns of geographic Variatio

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1996.tb01117.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Between 1984 and 1990 a total 221 Carlin tags used to mark salmonSalmo salarsmolts in the River North Esk, NE Scotland, were recovered from the stomachs of goosandersMergus merganserand red‐breasted mergansersM. serrator. Both Carlin‐tagging and adipose‐clipping affected the predation of salmon smolts by sawbill ducks. The mean (± S.D.) sizes of tagged smolts taken by both species were similar (117 ± 3 mm) and significantly smaller than the mean sizes of smolts in the river, possibly due to a reduction in the swimming performance of small smolts bearing tags. Large adipose‐clipped smolts (±mean smolt size) were predated significantly more than unclipped smolts, but no such difference was observed for small smolts (

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1996.tb01118.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Parental care of eggs by male upland bulliesGobiomorphus brevicepswas studied in the field and in the laboratory, with special emphasis on the effect of infection by trematode cysts. In the field, the proportion of old eggs in the nest affected the time taken by males to return to their nest after being chased away, but only in one year of the study. No effects of male size, male parasite load, number of eggs per nest or nest characteristics were observed. In the laboratory, heavily‐infected males spent more time fanning their eggs than lightly‐infected ones. Smaller males also tended to spend more time fanning than large males. Male size, parasite load and number of eggs per nest had no measurable effect on the aggressiveness of guarding males towards intruders, weight loss in males or egg incubation time. Parental investments did not vary as a function of age of the eggs. All males cannibalized some of their eggs, and there appeared to be a threshold brood size below which males consumed their entire brood. Overall, results were not consistent with those of studies on other fish species, and indicate that rules of investment in parental care may be different for fish inhabiting harsh, unpredictable environme

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1996.tb01119.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY