Determination of the Area Prospected by a Baited Trap from a Tagging and Recapture Experiment with Snow Crabs (Chionoecetes opilio)

Abstract

Time of hatching, abundance of recently-hatched larvae and their relative contribution from the Georges Bank and Nantucket Shoals spawning grounds, as well as mortality during the autumn-winter period are esti mated for eight spawning seasons on the basis of data from the ICNAF Larval Herring Surveys which were conducted during 1971-78. Indices show that the highest initial larval production occurred in 1973 and 1974 as a result of the large 1970 year-class and that there was a decline in production of about two orders of magnitude by 1976 and thereafter. The collapse of the fishery on Georges Bank in 1976 coincided with a deiay in peak spawning from mid-to late-October, a contraction of the spawning season, and a shift of the remaining spawning population to northwestern Georges Bank and Nantucket Shoals. Furthermore, the mean seasonal mortality rate of 5% per day, estimated over the first 6 months of life, varied significantly (3-7%/day) after the 1975 season. The initial larval production estimates are compared with abundance indices (age 3+ herring) from spring bottom-trawl surveys, and sources of bias are evaluated.

Retrospective length-based analysis of Bristol Bay red king crabs: Model evaluation and management implications

“…Our estimated effective fishing radius (EFR) of 78 m for Japanese traps, is generally comparable with those estimates for Chionoecetes opilio in Canadian Atlantic waters of 50-70 m by Brêthes et al (1985) and 69 m by Greendale and Bailey (1982), but it was larger than the 36 m estimated by Miller (1975).…”

Trapping of Small Organisms Moving Randomly

“…This estimate of plume reach agrees well with and refines that of up to 100 m arrived at by direct behavioral observations of sawflies released at various distances downwind and perpendicular to a line of traps (Östrand et al 2000). Our final detailed example comes from research (Brêthes et al 1985) conducted on snow crabs in the Gulf of St. Lawrence, just east of Quebec, Canada. In this study, an anchor was attached to one end of a long line, and one standard commercial snow crab trap (bait unspecified but probably some type of chopped fish) was attached 100 m up the line.…”

“…Traps were recovered and crabs counted after 24 h in one test and 48 h in another. 5.14 Untransformed (a) and Miller plots (b) of data from a single-trap, multiple-release test using snow crabs (Brêthes et al 1985). The data for several close release points at the mid-range of release distances were averaged to keep the distance increments nearly regular.…”

Red crab (Geryon maritae) density in 1985 by the technique of effective area fished per trap on the northern fishing grounds off South West Africa

“…During recent years attempts have been made at the Sea Fisheries Research Institute to achieve reliable estimates of stock density for the deep-sea red-crab fishery off South West Africa (Namibia). Recognized methods such as trawling (Beyers and Wilke 1980), photography (Melville-Smith 1983, 1985 and tagging have been employed with varying degrees of success to this end.…”