The Effects Of A Regulatory Gear Restriction On The Recruiting Year Class In The Sea Scallop, Placopecten Magellanicus (Gmelin, 1791), Fishery

In 1994, Amendment 4 to the sea scallop (Placopecten magellanicus) fishery management plan was adopted, which restricted fishing effort by controlling vessel days at sea. crew size, and gear size. Dredge ring size was increased from 76.2 mm (3.0 ) to 82.6 mm (3.25 ) in March 1994, and again to 88.9 mm (3.5 ) in January 1996 to increase the age of entry of scallops into the fishery. Between June 1994 and April 1995, four trips were taken on commercial scallop vessels in the western mid-Atlantic to determine harvest efficiency of 88.9-mm dredge rings relative to 82.6-mm dredge rings used in the fishery at the time. Our study focused on the abundant and nearly ubiquitous 3-year-old, 1990 year class. At the time, individuals in this year class were approaching the size (70 mm) of both full recruitment to the gear and recruitment into the fishery. Relative harvest efficiency of this year class ranged from 60% to 72% over the study period. The 88.9-mm rings were found to be 90% efficient when scallops had grown to a size of 100-105 mm. The 88.9-mm ring dredge would therefore delay full recruitment of the 1990 year class for almost 1 y relative to the 82.6-mm ring dredge. Analysis shows that this delay could increase yield-per-recruit by almost 10% and spawning stock biomass by 40% to 60%,. Benefits of the gear modifications will only be fully realized when used in conjunction with other measures that reduce or stabilize fishing effort

A Comparison Of Size Selectivity And Relative Efficiency Of Sea Scallop, Placopecten Magellanicus (Gmelin, 1791), Trawls And Dredges

During August and September 1997 and May 1998, three comparative fishing experiments were conducted aboard commercial sea scallop trawl and dredge vessels to assess the efficacy of gear restrictions found in Amendment 3 to the Sea Scallop Fishery Management plan (SSFMP). This amendment involved certain gear restrictions including minimum mesh and ring sizes and maximum Scar widths and was intended to equate the performance of sea scallop trawls and dredges with respect to size selectivity and efficiency. Statistical analysis indicated that selectivity and efficiency were not equal for the two gear types. while absolute gear size selectivity could not be estimated, there was clear evidence of differential relative size selectivity between the two gears. Relative harvest efficiency values shifted at 90 to 95 mm shell height. Trawl vessels were more efficient capturing sea scallops less than 90 mm, and dredge vessels were more efficient capturing sea scallops greater than 90 tnm. This shift in relative harvest efficiency coupled with an observed cull size at 70 to 75 mm shell height resulted in the bawl vessels being more dependent on age 3 sea scallops with shell heights of 70 to 90 mm. Operational differences observed between the two gear types restricted sea scallop trawl vessels to areas of smooth substrate. Large differences in both relative efficiencies and operational requirements will present considerable impediments to the desired outcomes of having equivalent performance between gear types