摘要:

Eremophilus mutisii uses the stomach for aerial respiration. Inspiration is during a rapid dash to and from the surface. Air‐breathing occurs in hypoxic and normoxic water, but is not obligatory. The evolution of a reduced swimbladder is associated with a benthic mode of life in E. mutisi

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1987.tb05236.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The importance of environmental ions to olfactory sensitivity in fish has not been clarified by electrophysiological experiments. We tested the ability of juvenile coho salmon,Oncorhynchus kisutch(Walbaum), to detect L‐serine after acclimation to either fresh water or sea water. The olfactory threshold was identical in the two waters, indicating that the sensitivity of olfaction was not affected by ionic content of the solutions bathing the sensory tissu

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1987.tb05237.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The diets and feeding periodicities of two small, riffle‐dwelling fish, the torrentfish,Cheimarrichthys fosteri, and the bluegilled bully,Gobiomorphus hubbsi, were investigated in an unstable, braided New Zealand river from May 1985 to April 1986. Aquatic insect larvae dominated diets of all fish and dietary overlap between species was high in 10 of 12 months. Nevertheless, the relative importance of prey items, as assessed by the index of relative importance (IRI), differed between species.Gobiomorphus hubbsifed almost exclusively on larvalDeleatidium(Ephemeroptera), whereasC. fostericonsumed a greater variety of prey items, withDeleatidiumand trichopteran, elmid and chironomid larvae numerically dominant. A dietary switch fromDeleatidiumto chironomid larvae occurred in both species during December 1985, when total and relative abundances of mayfly and other benthic macroinvertebrate larvae were severely reduced by two consecutive floods. A diel sampling programme indicated that the feeding periodicity of the two species differed:C. fosteriwas a nocturnal feeder, whereasG. hubbsiexhibited a strong crepuscular peak in feeding activity. Overall, the two fish partition their food resource weakly by consuming prey items in different proportions and sizes and more strongly by utilizing the food resource at different time

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1987.tb05238.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The annual reproductive cycle of the brown bullhead catfish,Ictalurus nebulosusLesueur, was investigated over a two‐year period. In females, GSI increased in the spring as follicles enlarged and the granulosa became hypertrophied, dropped during spawning in August, then rose in the autumn as follicles enlarged slightly. 3β‐Hydroxysteroid dehydrogenase (3β‐HSD) activity was limited to thecal nests of large, vitellogenic follicles. Plasma testosterone and estradiol‐17β levels increased in parallel with GSI. Levels of both steroids dropped prior to the spawning period, although a peak in estradiol‐17β was evident during the spawning period. No 11‐ketotestosterone was detected in female plasma. In males, GSI increased in the spring as spermatogenesis proceeded, and dropped during spawning. 3β‐HSD activity was confined to Leydig cells and was most intense prior to spawning. Plasma testosterone and 11‐ketotestosterone peaked during the pre‐spawning period, dropped prior to spawning, then rose slowly during the autumn. A peak in estradiol‐17β occurred during the spawning period. Significant differences in GSI and plasma steroid levels during the pre‐spawning and spawning periods were observed between the two yearly cycles; they may be related to differences in ra

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1987.tb05239.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Lough Hyne marine reserve is a sea inlet, of areac.60 ha, on the south‐west Irish coast. Conditions vary from the exposed outer harbour of Barloge Creek to a sheltered marine basin, with depths to 47 m. A shallow, narrow connection, the Rapids, between the two parts causes a reduced tidal range within the marine basin. The status of 72 fish species is given, 38 of them being recorded for the first time from this locality. Eleven goby species are present, including well established but isolated populations ofGobius cruentatusandG. couchi.The listing comprises museum material, previous records and direct observations from 1976 to 1985 inclusive. This reserve is recognized by the Council of Europe as part of an international biogenetic network of reserve

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1987.tb05240.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Upstream spawning migrations of mature brown trout,S. trutta, and rainbow trout,S. gairdneri, were studied in Liawenee Canal, Great Lake from 1949 to 1985. Brown trout migrations normally occurred from early April to mid‐May and rainbow trout from late August to early November. In 1983, 16 425 brown trout and 1338 rainbow trout passed through a fixed upstream diversion trap. Brown trout spawning migrations occurred predominantly over the temperature range 6–10° C, while rainbow trout migrated predominantly over the range 5–11° C. Migrations peaked at water temperatures of 7.6°C (males) and 7.8°C (females) for brown trout, and 8.3°C (males) and 9.6°C (females) for rainbow trout. Rainbow trout migrations occurred at high flow conditions and were positively correlated with canal flow increases, while brown trout migrated under low canal flow. Mean length, weight and condition of rainbow trout of both sexes decreased significantly during migrations. Female brown trout decreased in weight and condition but not in length; male brown trout did not change in condition despite decreases in both length and weight during migrations. Overall sex ratio was 2:1 (female:male) for both species, with the relative proportion of male fish decreasing as migrations progressed. Age composition changed during migrations; dominant age classes were 3<4<5 + years for both species. Comparison of length, weight, condition and age revealed minor changes during the 37‐year per

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1987.tb05241.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Two‐hundred‐and‐forty rainbow trout,Salmo gairdneri, were exposed for 30 days to sublethal concentrations of the pesticide endrin. On day 30, ten fish from each treatment group were sacrificed and examined for the ability of peritoneal macrophages to phagocytize latex beads. The remaining fish were immunized with 10 μg ofYersinia ruckeriO‐antigen, and exposure to endrin continued. The migration inhibition factor assay (MIF), plaque forming cell assay (PFC), and serum agglutination titres (SAG) were performed 2, 14, and 30 days post‐antigen inoculation. Serum was collected from all fish for serum cortisol concentrations. Endrin exposure had no effect on the phagocytic ability of peritoneal macrophages. However, the MIF, PFC and SAG responses were significantly reduced from control values. Serum cortisol concentrations were found to be significantly elevated in endrin‐exposed fish. Serum cortisol concentrations were found to be significantly higher on days 44 and 60 (192 and 194 ng ml−1, respectively) when compared to days 30 and 32 (159 and 141 ng ml−1, respectively). Cortisol values for days 30 and 32 did not differ significantly, nor did those of days 44 and 60. The relationship between elevated serum cortisol concentrations and endrin exposure on the immune respo

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1987.tb05242.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The effect of altering serum cortisol concentrations on the immune response was elucidated in endrin‐ and non‐endrin‐exposed rainbow trout,Salmo gairdneri.Fish were immunized with 10 μg ofYersinia ruckeriO‐antigen following 30 days of treatment. The migration inhibition factor assay (MIF), plaque‐forming cell assay (PFC) and serum agglutination titres (SAG) were performed 2, 14 and 30 days post‐antigen inoculation. Endrin exposure was continued subsequent to antigen inoculation. Control fish were fed 20 and 35 mg kg−1body weight day−1of cortisol and metyrapone, respectively. Endrin‐exposed fish received 35 mg kg−1body weight day−1of metyrapone in their diet. Control fish receiving cortisol had significantly reduced MIF, PFC and SAG responses. The MIF response was completely restored in endrin‐exposed fish receiving dietary metyrapone. The PFC response and SAG titres were partially restored, 61 and 69% respectively, in endrin‐exposed fish receiving metyrapone. The results indicate that elevated serum cortisol concentration obtained in endrin‐exposed fish has a central role in repre

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1987.tb05243.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

English sole,Parophrys vetulus, from eight locations within Puget Sound, U.S.A. were examined for histological abnormalities of the liver and kidney. A total of 1083 fish were collected between February 1979 and June 1984 in nine separate sampling periods. Idiopathic lesions, i.e. lesions of unknown cause, were classified into eight hepatic and four renal lesion categories. The significance of certain potential risk factors associated with lesion prevalences, including age, gender, site of capture, season of capture and year of capture, were assessed by logistic regression. The odds ratios for the significant risk factors were also calculated. Site of capture and age of the examined fish were found to be the most important factors for most of the observed lesion types, e.g., hepatic neoplasms and foci of cellular alteration, whereas year and season of capture were significant influences for only a few lesion types, e.g., specific and nonspecific degenerative/necrotic lesions of the liver. Gender of examined fish was not found to be a significant factor for any of the lesion types. These results emphasize the importance of including certain potential influences, such as age and season of capture, in the analysis of field‐collected organ pathology dat

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1987.tb05244.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

From May to October 1983 the migration of six adult bream was examined by long‐term ultrasonic tagging experiments. Two different migration types were observed: diurnal rhythmical migrations between the littoral and pelagic zones, and sporadic locomotions such as spontaneous excursions of several kilometers distance. At night, during their sojourn in the shallow littoral zone, bream feed intensively on benthic organisms; during their stay in the pelagic areas they presumably feed on zooplankton. Sporadic changes of place enable the bream to feed on locally abundant food resources. During the spawning season, migration contributes to successful spawnin

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1987.tb05245.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY