ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1996.tb06063.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The reproductive biology of roundnose grenadierCoryphaenoides rupestriswas investigated against a background of increasing commercial exploitation. Samples were taken from surveys carried out in Rockall Trough between 1993 and 1995. An eight‐point maturity scale was developed based on both visual inspection of the ovaries and histological screening. The various stages of development of roundnose grenadier oocytes were described and the relative proportion of oocyte types and their respective size range in each maturity stage were investigated. The dynamic organization of the ovary indicated a determinate maturation cycle in this species. Population spawning appears to be prolonged, extending from July to at least November. However, data were insufficient to clarify individual spawning duration. The potential fecundity of 29 mature fish ranged from 11 083‐55 175 (63‐95 cm total length). The results were very similar to previous values from the North Atlantic. The reproductive strategy of the roundnose grenadier is discussed in the light of the current commercial exploitation of the Sp

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1996.tb06064.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Sillago robustaandS. bassensisoccupy the open sandy areas of the deeper waters (20–35 m) of the inner continental shelf of the lower west coast of Australia. Comparisons were made of their age and size compositions, growth rates, ages and sizes at first maturity, and spawning times. MostS. robustawere less than 3 years old (maximum 7 years), whileS. bassensisoften reached 7 years of age (maximum 10 years). The maximum length ofS. robusta(200 mm) was far shorter thanS. bassensis(328 mm), whereas the reverse pertained for the von Bertalanffy growth coeffcient (K), i.e. c. 1.0 v. c. 0.3. Differences in K reflect the fact that c. 80% of the asymptotic length is achieved byS. robustaafter 2 years, but not until 6 years of age byS. bassensis.Sexual maturity was reached by up to 50% ofS. robustaat the end of their first year of life, and by almost all fish at the end of their second year of life. MostS. bassensisdid not reach maturity until the end of their third year of life. In both species, those individuals that reached maturity early, were significantly longer than those that did not reach maturity at the same age. The gonadosomatic indices and proportions of mature gonads, and the numbers of vitellogenic and hydrated oocytes and post‐ovulatory follicles, were relatively high in ovaries of both species between December and March. Although both species spawn in these 4 months, someS. bassensisalso spawn between September and November and in March and April. In the middle of the spawning period, the ovaries ofS. robustaandS. bassensisfrequently contained oocytes that ranged widely in size and development, together with post‐ovulatory follicles, suggesting that both species are multiple spawners. Juveniles ofS. robustaremain in the deeper waters of the inner continental shelf, whereas those ofS. bassensismigrate inshore to their nursery areas in surf zones. AsS. robustareaches sexual maturity at an earlier age and smaller size thanS. bassensis, it is probably more advantageous for the juveniles of this species to remain in deeper water, and thereby conserve energy for gonadal maturation, rather than migrating into shallow waters for only a very few m

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1996.tb00002.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The reproductive cycle of anglerfish was studied by examining fresh material obtained from commercial landings and research vessel surveys. The general morphology and histology of the gonads are described. This species has unusual gonads. The testes are tubular, and beanshaped in transverse section. The maturation process of the testis is similar to that of most other teleosts. The ovaries are confluent and form a single, flattened tube. During maturation, the width and, in particular, the length of the ovaries increases dramatically. A gelatinous matrix is produced during the maturation process, which contributes to the enormous size and weight of ripe ovaries. Ripe testes can be found throughout the year, whereas ripened ovaries were found only between November and May. Females outnumbered males in length classes greater than 70 cm and no males larger than 90 cm were found. The estimated mean length at maturity (150%) was 73 cm for females and 49 cm for males. Because only the large female anglerfish are capable of spawning, and because virtually all large anglerfish are female, trends in their abundance resulting from commercial exploitation should be monitored with care.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1996.tb06065.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Hatchery brown troutSalmo trutta(1406) of length 5–20 cm were released into a 7.5 ha shallow lake. They were recaptured with 28 multimesh gillnets of a type proposed for use in the Nordic countries and 42 single gillnets of mesh size 8–22 mm (knot to knot). Corrected for the effect of different twine thicknesses, the single nets showed the highest selectivity for 16.5 mm and smaller meshes and the multimesh nets for the larger meshes. The height of the selectivity curves increased exponentially with mesh size, and most distinctly for the multimesh nets. Over a limited range of mesh sizes the selectivity of the two types of net did not differ much. Extended over mesh sizes 10.0–55.0 mm, the catching abilities of the two types of net became considerably diff

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1996.tb00003.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Deep‐water habitats form by far the largest ecosystems on the planet. Enough is known about the lives of deep‐water fishes, despite the difficulties inherent in such study, to give a fairly coherent picture of their overall ecology. Inferences based on individual morphology and taxonomic diversity provided the first clues, but series from the various large national deep‐water expeditions have allowed the working out of detailed life histories, food webs, species associations and biogeography. The particular conditions that characterize deep water everywhere have shaped the nature of deep‐water fishes, and probably the most important factor at play has been the logarithmic decline of food energy available with increasing depth. Comparative study of deep‐pelagic, deep‐demersal, and deep‐lake fishes reveals interesting and intriguing differences with respect to the adaptations and probable history of the faunas in each of these habitats. Deep‐water fishes have long been insulated from any significant human impacts, but deep‐water fisheries, species introductions, pollution and other ecosystem tamperings are changing this situation rapidly. Can these remarkable, enduring and well‐adapted species and assemblages withstand the d

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1996.tb06066.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Wrasse used as cleaner fish with farmed Atlantic salmonSalmo salarcan be subjected to large and rapid temperature and salinity fluctuations in late autumn and early winter, when summer‐warmed surface water is affected by early snowmelt episodes. Because of their containment in sea cages, wrasse which are essentially acclimated to summer temperatures may be rapidly exposed to winter conditions. Short‐term tolerance of low temperature and low salinity by three species of wrasse, goldsinnyCtenolabrus rupestrisrock cookCentrolabrus exoletuscorkwingCrenilabrus melopscaught during the summer, and winter‐caught corkwing, was investigated. A 3–day period at 30 or 32‰ salinity and temperature 8, 6 or 4° C (for summer‐caught fish; 4° C only for winter‐caught) was followed by a decline in salinity to 24, 16 or 8‰ over c. 36 h, followed by a further 24 h at these salinities held constant, at each of the three temperatures. Controls in 30 or 32‰ were maintained at 8, 6 or 4° C. Mortality of summer‐caught corkwing and rock cook was high at 4° C, whereas the influence of salinity on mortality was small. Mortality of goldsinny was low or zero in all treatments. Surviving corkwing and rock cook after 3 days at 4° C and 32‰ salinity had elevated plasma osmolality: in summer‐caught corkwing, plasma [Cl°] and [Na+] were high, whereas in rock cook only [Na+] was high. Haematocrit was low in summer‐caught corkwing, high in rock cook. In survivors of all three species at the end of the experiment, values of all these parameters were comparable with those of fish at the beginning of the experiment, except that survivors at low salinity (8, 16‰) had low plasma osmolality, at all temperatures, and in surviving rock cook in these treatments haematocrit was high and plasma [Cl−] was low. Winter‐caught corkwing had higher osmolality, [Na+] and [Cl−] than summer‐caught corkwing; there was no difference in haematocrit. Survival of wintercaught corkwing exposed to four salinities at 4° C was much higher than that of summercaught corkwing under the same conditions. Little change in blood physiology was recorded for winter‐caught corkwing, with only fish subjected to 8‰ and 4° C showing signs of osmoregulatory stress. The interspecific and seasonal differences in survival and blood physiology at low temperature and low salinity are discussed in relation to wrasse survival ove

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1996.tb00004.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

A review of energy use and the life histories of deep‐water demersal fishes suggests that there are two primary groups or guilds; those that live dispersed over the sea floor and those that aggregate in association with topographic features like seamounts. Dispersed deep‐sea fishes typically have a body plan designed for slow cruising or ‘sit and wait’ predation, and are characterized by very low energy stores and metabolic rates. Scaled for body size, the metabolism of these fishes was comparable to that of bathypelagic fishes. On the other hand, aggregatory deep‐water species are characterized by robust morphology and strong locomotory ability to maintain themselves in environments characterized by strong, variable currents. Their flesh has high protein and lipid but low water content. The metabolic rate of orange roughy, an aggregating deep‐water species, was substantially higher than that of dispersed deep‐water fishes and was comparable to that of haddock, a shelf demersal species. However, although the estimated ration of orange roughy was higher than that of dispersed demersal deep‐water species, its growth rate was comparable and its growth efficiency was far lower due to its high metabolic costs. Large deep‐water dispersed fish species are characterized by late maturity and an extended reproductive period, but these characteristics are less pronounced than in deep seamount‐associated species, which may live in

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1996.tb06067.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

GoldsinnyCtenolabrus rupestriswere subjected to rapid, environmentally realistic, reductions in temperature at 2° C increments from 10 to 4° C over a 3‐day period in full‐strength sea water. In separate experiments, oxygen uptake measurements and ultrasound recordings of heart rate and opercular motion were carried out at regular intervals over the same temperature regime. Mean oxygen uptake rates fell from 0.042 to 0.028 ml O2g−1h−1between 10 and 6° C respectively (Q10=2.71). Between 6 and 4° C mean rates decreased from 0.028 to 0.008 ml O2g−1h−1(Q10=542). Mean opercular motion and heart beat rates decreased from 49.5 and 60.3 beats min−1respectively at 10° C to 18.7 and 18.0 beats min−1respectively at 4° C. Most goldsinny subjected to 4° C were observed in a torpid state and would not react to external stimulation. Opercular motion was erratic at 4° C and would at times cease altogether for periods up to 1.3 min duration. Heart movement was diffcult to detect at 4° C and may also have ceased for prolonged periods. Q10values for opercular motion and heart beat rates recorded between 6 and 4° C were 6.39 and 24.52 respectively compared with values of 2.42 and 2.93 respectively recorded between 10 and 8° C. Such large depressions in metabolism appear not to have been reported previously for a marine fish species. No goldsinny mortalities were recorded at any temperature. The possibility that hypometabolic torpor is an adaptive strategy for goldsinny survival at low environmental

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1996.tb00005.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

A total of 168 bottom longline operations were carried out at depths between 72 and 1102 m during four cruises off Lanzarote and Fuerteventura, Canary Islands. One hundred and twenty‐eight operations were successful, resulting in the capture of 1167 fishes belonging to 55 species. Clear variations in fish total weight and number, species richness and diversity, and the relative abundance of single species occurred among five different depth zones between 100 and 1100 m. The particular platform topography of the Canary Islands may affect the density and diversity of slope‐dwelling fishes. Whereas fish body length and weight showed an overall increase with depth, no such trends were found at the level of individual species. One species,Lepidopus caudalus, even revealed a bigger‐shallower trend. Among three species of trichiurids, depth distribution patterns were detected that may reflect vertical space partitioning. In October 1995, an unusually high number ofMora morowith advanced gonadal maturity were collected off eastern Fuerteventura at 997 m depth. At lesser depths and during other seasons, only a few individuals of this species were caught in the same area. This indicated a seasonal variability in local abundance that is most probably related to reproduction.Mora morohas an excellent flesh and may represent a valuable fisheries resource. Open problems requiring further research in the study area such as selectivity effects of the fishing gear and possible influences of ecological factors on geographical distribution of the deep‐water ichthyofauna, as well as important aspects of the future demersal fisheries management in the Canarian archipelago are briefly o

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1996.tb06068.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY