摘要:

Seventeen day old rainbow trout fry,Oncorbynchus mykiss, were subjected to four feeding regimes during 13 days at‐10° C: continuously fasted; delayed fed after 6 days fasting; fedad libitumwith Trout Chow #3 three (at 08: 00, 12: 30 and 17: 00 h); or six (08: 00, 10: 00, 12: 00, 14: 00, 16: 00, and 18: 00 h) times a day. Total RNA and DNA concentrations of the fry were measured by fluorometry at two day intervals. Fed fry continuously grew from ∼ 99 mg to over 200 mg after 13 days, but starved fish underwent growth loss of‐73 mg. Their condition factors (K) increased from ∼2.2 to ∼7–8 for the fed, and decreased to ∼1.9 for the fasted fish. Specific growth rate per day (SGR) increased from 0.05 mg to‐33.6 mg for the continuously fed fry six times a day (average 9.8% per day) and 29.7 mg for the fry fed three times a day (8.5%), but‐1.15 mg for the fasted fry (‐1.96%). Fed fish starved for 6 days, recovered their SGR after three days following feeding (day‐9), but did not catch up to the continuously fed fish (‐0.73%). DNA concentrations increased from‐450 μgmg per fish to‐600 μgmg for the starved fish,‐440 μg mg for the delayed fed, and‐290 μg mg for the continuously fed fish. RNA concentrations were ∼466 μg‐mg for the starved,‐840 μgmg for the re‐fed, and‐960 μg. mg for the fed fry. RNA/DNA ratios changed from 1.72 to 0.73 for the starved, 1.96 to 1.91 for the delayed feeding, and 1.8 to 3–3 for the fed three times a day, and 1.8 to 3.4 for the fed six times a day after 13 days. No significant differences existed between the fish fed three and six times a day. The results confirmed that SGR, total weight increment, and K were all higher in fed fish than in starved, indicating that feeding has a great influence on RNA/DNA ratio as physiological index in rainbow trout fry.

ISSN:1125-0003    

DOI:10.1080/11250009809386877

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The rich and diverse fish resources of Oman constitute its main natural resource after oil and natural gas. A total of 1142 species were identified, distributed among 520 genera and 164 families. Most of these are marine with broad geographical distribution; only four are freshwater species (Cyprinion micropthalmum, Garra barreimie, G. longispinnis, andOreochromis aureus).The ichthyofauna of Oman is characterized by large number of species in 21 families, comprising 92.6% of the estimated total number of marine families of the whole Indo‐Pacific region, and 49.9% of the worldís marine families. The Arabian Sea and Gulf of Oman are more diverse in fish species (‐1000 fish species) than the Arabian Gulf (> 500 fish species). More than 400 species are demersal, 511 species inhabit coral reefs and coastal lagoons, two are mesopelagic species, and the remainder are pelagic (157), bathypelagic (30), and bathydemersa] (7 species). Current fishing effort levels on some target species are either close to maximum sustainable yield or exceed it. A shift in species composition has resulted in declining landings of some high value fishes. A pilot aquaculture program has just started with the introduction of sea bream,Sparus aurataand tilapiaOreochromis aureus.Fisheries management is hampered by lack of appropriate management regulations, enforcement, and data on most stocks. Coastal habitats are being threatened by both natural and man‐made impacts. Fisheries research programmes are directed to fish taxonomy, ecology, biology, and stock assessment of some commercially important species. An extensive fish database and reference collection are currently being established at Fisheries Science and Technology Department, Sultan Qaboos University. Local human resources are needed to support the rational development and management of fishery resources.

ISSN:1125-0003    

DOI:10.1080/11250009809386878

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Large reservoirs are increasing in number in South America and Brazil, and are exploited by fishers. The River Piracicaba receives several pollutants discharged from industries and residences, and had its downstream portion dammed in 1962. This study is about the giilnet fishery located at the impounded portion of the River Piracicaba, and the possible influences of habitat alterations on the fish catch composition. Fish landings were recorded three days each month between October 1994 and September 1995. Data on the weight of fishes caught (kg per species) in 248 fish landings were collected. The catch of the large migratory catfishes (Siluriformes) decreased in the last 10 years, probably because of the interruption of their migratory route by the impoundment. Migratory Characiforms, on the other hand, have increased in the fishery. The river organic pollution probably favoured the spread of fishes that can adapt to low oxygen conditions. Forest clearance, which reduces forestry food resource availability, could be decreasing omnivorous fishes in the fishery. Fish landings in the River Piracicaba fishery suffered change in its composition in the past 11 years. The environmental alterations that had occurred in the Piracicaba River basin, like impoundment, pollution, and deforestation, can be important factors influencing such changes.

ISSN:1125-0003    

DOI:10.1080/11250009809386879

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The presence of anglers in Alto Lindoso reservoir, at the Peneda Geres National Park, was noted during the entire fishing seasons of 1995 and 1996. Anglers presence was irregular, more intense on weekends and holidays, declining as the season progressed. Site choice was mainly determined by road accessibility. Inadequate fishing conditions, the poor and irregular catch results, and the changes in the fish community of the recent Alto Lindoso reservoir might be the causes for the observed decline of angler competition. Study of the fish community, based on angleris catch and gill net samples, revealed that the fish community was mainly formed by Iberian cyprinids. Angling appraisal and knowledge of the fish communities is needed before the development of a correct management strategy.

ISSN:1125-0003    

DOI:10.1080/11250009809386880

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The brown trout population of the River Gallo (central Spain) was monitored every two months during 1996 to determine the current impact of angling. To evaluate the influence of additional parameters, physical habitat and food availability were also studied. To assess fishing pressure, trout harvest and angling exploitation, a partial creel census was conducted during the 1996 fishing season. Differences were found in densities and biomass between exploited (1182.4 fish ha‐1, 68.3 kg ha‐1) and unexploited areas, the latter being markedly higher (3135.1 fish ha‐1, 208.2 kg ha‐1). Production was quite superior in the unexploited area and decreased (from 144.5 kg ha‐1yr‐1to 37.2 kg ha‐1yr‐1) as fishing pressure increased. However, no consistent differences were observed in growth, condition factor, age diversity, mortality, recruitment age and turnover ratio. Sport fishing seems to be the main negative factor influencing the balance within population of brown trout in the River Gallo and therefore management should be focused on more restrictive angling measures.

ISSN:1125-0003    

DOI:10.1080/11250009809386881

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The Danube roach,Rutilus pigus virgo(Haeckel, 1852), lives in all watercourses of the Danube River basin in Slovenia. It is the most common caught sport fish in some waters. Catch of the Danube roach has decreased in recent years both by number and weight. The weight of an individual caught fish has increased. Numbers and weight of Danube roach dropped from 1990 to 1996, from 17 118 to 12 030 individuals and from 11 500 kg to 9 500 kg. Individual fish weights in the same period from 0.59 kg to 0.79 kg. According to the Red List of Slovenian Freshwater Fishes and Lampreys, the Danube roach falls into the vulnerable category (V). It is mainly threatened by pollution and river regulation.

ISSN:1125-0003    

DOI:10.1080/11250009809386882

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Rutilus rubilio, recently introduced into Sicily, is now widespread in many man‐made basins and watercourses of the island. We investigated a population living in a man‐made hypertrophie basin of southwest Sicily (Lake Arancio) in 1995. Sampling was monthly by a trawl and trammel net. Morphometric and meristic features were taken, and sagittal otoliths were extracted to assess age.R. rubiliorepresented the dominant species in the fish community of the man‐made basin. The population was characterized by a slower isometric growth, as related to age, than the population of South Italy.Rutilus rubiliobecame naturalised successfully and has contributed in altering the composition of the fish community described in 1977 by Faranda.

ISSN:1125-0003    

DOI:10.1080/11250009809386883

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:1125-0003    

DOI:10.1080/11250009809386884

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:1125-0003    

DOI:10.1080/11250009809386885

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:1125-0003    

DOI:10.1080/11250009809386786

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor