The Selectivity of Different Fishing Gear used in Lofoten
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ABSTRACT: Fishing trials with monofilament gill nets and longlines using small hooks were carried out in Algarve waters (southern Portugal) over a one-year period. Four hook sizes of "Mustad" brand, round bent, flatted sea hooks (Quality 2316 DT, numbers 15, 13, 12 and 11) and four mesh sizes of 25, 30, 35 and 40 mm (bar length) monofilament gill nets were used. Commercially valuable sea breams dominated the longline catches while small pelagics were relatively more important in the gill nets. Significant differences in the catch size frequency distributions of the two gears were found for all the most important species caught by both gears (Boops boops, Diplodus bellottii, Diplodus vulgaris, Pagellus acarne, Pagellus erythrinus, Spondyiosoma cantharus, Scomber japonicus and Scorpaena notata), with longlines catching larger fish and a wider size range than nets. Whereas longline catch size frequency distributions for most species for the different hook sizes were generally highly overlapped, suggesting little or no differences in size selectivity, gill net catch size frequency distributions clearly showed size selection. A variety of models were fitted to the gill net and hook data using the SELECT method, while the parameters of the logistic model were estimated by maximum likelihood for the longline data. The bi-normal model gave the best fits for most of the species caught with gill nets, while the logistic model adequately described hook selectivity. The results of this study show that the two static gears compete for many of the same species and have different impacts in terms of catch composition and size selectivity. This information will I;e useful for the improved management of these small-scale fisheries in which many different gears compete for scarce resources.Scientia Marina 01/2003; 67(3):341-352. DOI:10.3989/scimar.2003.67n3341
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ABSTRACT: Research vessel survey data from the northern Grand Bank and southern Scotian Shelf/Bay of Fundy were analysed for evidence of the occurrence of shoals of Atlantic cod (Gadus morhua) with unequal sex ratios during the spawning season. Cod were found to Form both male dominated and female dominated shoals during spawning. In both areas, female dominated shoals were found in significantly deeper waters. A higher proportion of both males and females were in spawning condition in the male dominated fishing sets and a higher proportion of females had completed spawning in the female dominated fishing sets. Males may arrive at the spawning area first, with females moving into the area when ready to spawn and then returning to deeper, warmer water once they have completed spawning. (C) 1996 International Council For the Exploration of the SeaICES Journal of Marine Science 10/1996; 53(5):820-826. DOI:10.1006/jmsc.1996.0103
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ABSTRACT: A comprehensive aging study of vermilion snapper, Rhomboplites aurorubens, was conducted, using 1,465 otoliths collected between 1991 and 1995 from the commercial and headboat fisheries from North Carolina through the Florida Keys. An additional 19 otoliths came from fishery-independent samples from the South Atlantic Bight for fish smaller than 254 mm total length (TL), which is the legal size limit. Marginal increment analysis revealed that rings on the otoliths were deposited annually. This observation is further substantiated by the increasing modal radius of each age ring corresponding to the increasing modal size of the fish at age. Observed ages ranged from age 1 (202 mm mean TL) to age 14 (535 mm TL). The largest fish was 600 mm TL and was estimated to be age 13. The weight–length relationship was described by the equation: W = 9.55 × 10(L), where W = whole weight in kilograms and L = total length in millimeters. The von Bertalanffy equation was estimated using the inverse, weighted, back-calculated lengths at the last annulus. The equation was Lt = 650 (1−e ), where t is age in years.Transactions of the American Fisheries Society 09/1998; 127(5):787-795.