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海洋学   3篇
  2013年   3篇
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A total of 248 roving creel surveys along the length of the Berg River Estuary, in the Western Cape, South Africa, recorded 626 shore-angler and 88 boat-angler outings over the period December 2002–November 2005. Catch-and-effort information was obtained from catch inspections with 360 handline and 246 rod-anglers. Average total annual linefishing effort was estimated at 449 ± 29 (mean ± SE) boat-angler days, 1 299 ± 118 recreational shore-angler days and 1 394 ± 57 subsistence (handline) shore-angler days. The estimated total shore-based linefish catch (excluding boat-based catches) from the estuary for the years 2004 and 2005 was 37 231 ± 1 326 fish and 26 938 ± 706 fish (approximately 8 t and 7 t) respectively. Compared with other estuaries along the South African east coast where angler catches have been surveyed, species diversity in catches from the cool-temperate Berg River Estuary was low, with only 15 species caught, of which three, elf Pomatomus saltatrix (56%), harder Liza richardsonii (31%) and carp Cyprinius carpio (11%), dominated the catch. Average linefish catch per unit effort of most species increased significantly in the two years subsequent to the closure of the long-existing commercial gillnet fishery in March 2003. Length frequency distributions revealed significant increases in the average size and an increased contribution of larger size class elf and harder to the linefish catch over the monitoring period, suggesting a degree of recovery of the estuarine icthyofauna after more than a century of intensive gillnet fishing.  相似文献   
2.
Boat-based creel surveys were used to collect catch and effort data on the shore- and boat-based linefisheries of the Kromme, Gamtoos, Swartkops, Sundays, Bushmans, Kariega, Kowie and Great Fish estuaries in the Eastern Cape, South Africa, from January 1996 to April 1997. The surveys, which were performed primarily during routine fisheries law enforcement patrols by a regional conservation agency, recorded the catch and effort of 2 468 individual angler outings (12 840 angling hours) during 337 angler-count patrols. Although 26 species were recorded, a large proportion of the catch (85%) comprised only four species. Spotted grunter Pomadasys commersonnii (43%) was most commonly caught, followed by Cape stumpnose Rhabdosargus holubi (16%), dusky kob Argyrosomus japonicus (14%) and white seacatfish Galeichthys feliceps (12%). In terms of mass, the overall catch was dominated by A. japonicus (50%) and P. commersonnii (33%). Overall catch per unit effort (cpue) by number was highest during summer and lowest during winter, and vice versa for cpue according to mass. Angler counts showed the Sundays Estuary had the highest mean angling effort for both weekdays and weekends (10.1 and 22.9 anglers count?1 respectively). The Gamtoos Estuary had the lowest count for weekdays (5.5 anglers count?1) and the Kariega Estuary the lowest for weekends (9.8 anglers count?1). Shore-based was more popular than boat-based angling (59% compared to 41%), and all estuaries had substantially higher angling effort on weekends than on weekdays. Angling with bait (93.3%) was more popular than lure- or fly-angling (6.7% combined). Considerations for management of A. japonicus in the Eastern Cape estuarine linefishery are presented.  相似文献   
3.
An assessment of catch and effort in the Eastern Cape shore and skiboat linefisheries was undertaken between 1994 and 1996 by means of roving creel and access point surveys. Catch-and-effort data were obtained from direct observation of 3 273 shore-fishers, 172 recreational and 223 commercial skiboat outings. Total effort in the region was high at 903 186 fisher-days year?1 in the shore fishery and 64 266 and 24 357 fisher-days year?1 in the commercial and recreational skiboat sectors respectively. The fisheries are multispecies in nature. The shore fishery consisted of 66 species, the recreational skiboat fishery 44 species and the commercial skiboat fishery 48 species. Just 10 species accounted for 75, 83 and 90% of the catch of the shore, recreational and commercial skiboat fishery respectively. The average catch per unit effort (cpue) was low in all sectors, 1.15 kg fisher?1 day?1 in the shorefishery, 9.4 kg fisher?1 day?1 in the recreational skiboat fishery and 21.5 kg fisher?1 day?1 in the commercial skiboat fishery. Catch data showed that professional and club anglers are more successful fishers. Comparisons with historic records for Port Elizabeth revealed that the cpue in the shore fishery had declined markedly, whereas the total effort increase was negligible (0.1%). In addition, the species composition of the fishery has changed.  相似文献   
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