Gear Selectivity of a Longfin Squid Bottom Trawl

Metadata Updated: February 27, 2019

Loligo pealeii (longfin inshore squid) co-occurs with Atlantic butterfish (Peprilus triacanthus) throughout the year and discarding in the L. pealeii bottom trawl fishery is the primary source of fishing mortality on the butterfish stock. Consequently, a codend mesh size increase in the Loligo fishery has been proposed as a management measure to minimize discarding of butterfish and other bycatch species. A paired-tow study was conducted using a Loligo twin trawl to assess the effects of a codend mesh size increase, from 50 mm to 65 mm (inside stretched mesh), on catch rates and size selection of the target and bycatch species. Relative mesh selection factors estimated from a SELECT model were: 1.7, 1.5, 2.2, and 3.0 for L. pealeii; P. triacanthus; Illex illecebrosus (Northern shortfin squid); and Merluccius bilinearis (silver hake), respectively. Catches of butterfish and silver hake in the 65 mm codend were reduced by 58% and 41% in terms of numbers, respectively. However, a larger mesh size would be necessary to allow 50% escapement of the median sizes of mature silver hake and butterfish. A trade-off associated with the bycatch reductions is a 29% loss in the catch weight of the target species. However, the reduction in ex-vessel value of Loligo catch is probably not proportional to the percent loss in Loligo catch because most of the loss consisted of squid from the smallest market size categories which have the least value and are primarily discarded. In addition, a greater percentage of large, more valuable squid was caught in the 65 mm codend. The September study results likely represent a worst-case scenario with respect to Loligo catch loss because the monthly mean body size of Loligo tends to be smallest during September. Most catches of the three bycatch species evaluated herein and Loligo smaller than 10 cm are discarded, most likely dead, in the Loligo fishery. Therefore, a codend mesh size increase to 65 mm should provide some conservation benefits to these stocks if a portion survive escapement. On a fleet-wide basis, the magnitude of bycatch reductions and Loligo catch loss will vary depending on seasonal changes in mean body size, vessel- specific gear characteristics and fishing practices.

Access & Use Information

Downloads & Resources

Dates

Metadata Date September 6, 2018
Metadata Created Date March 28, 2016
Metadata Updated Date February 27, 2019
Reference Date(s) (publication)
Frequency Of Update asNeeded

Metadata Source

Harvested from NOAA CSW Harvest Source

Additional Metadata

Resource Type Dataset
Metadata Date September 6, 2018
Metadata Created Date March 28, 2016
Metadata Updated Date February 27, 2019
Reference Date(s) (publication)
Responsible Party Northeast Fisheries Science Center (Point of Contact, Custodian)
Contact Email
Access Constraints Access Constraints: User must read and fully comprehend the metadata prior to use. Applications or inferences derived from the data should be carefully considered for accuracy. NEFSC Data Access Constraint: If data is stored on an internal NEFSC network, the requester may not have direct access to query the data unless they are also authorized for network access. | Use Constraints: Acknowledgement of NOAA/NMFS/NEFSC, as the source from which these data were obtained in any publications and/or other representations of these, data is suggested.
Bbox East Long -71.253833
Bbox North Lat 40.746565
Bbox South Lat 38.311567
Bbox West Long -73.82214
Coupled Resource
Frequency Of Update asNeeded
Guid gov.noaa.nmfs.inport:27378
Harvest Object Id 3e52c8ee-1e18-4c23-85cc-96eda623d3d2
Harvest Source Id 2aed8e29-fc5b-4cde-aa66-fb1118fd705e
Harvest Source Title NOAA CSW Harvest Source
Licence NOAA provides no warranty, nor accepts any liability occurring from any incomplete, incorrect, or misleading data, or from any incorrect, incomplete, or misleading use of the data. It is the responsibility of the user to determine whether or not the data is suitable for the intended purpose.
Metadata Language eng
Metadata Type geospatial
Progress completed
Spatial Data Service Type
Spatial Reference System
Spatial Harvester True

Didn't find what you're looking for? Suggest a dataset here.