The seasonal distribution and abundance of barndoor skate on Georges Bank based on scallop dredge surveys

Barndoor skate (Dipturus laevis) is one of the largest skate species in the Northwest Atlantic, and seasonal trawl surveys have identified Georges Bank as critical barndoor skate habitat. We examined fine-scale changes in the seasonal distribution and relative abundance of barndoor skate in the scal...

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Bibliographic Details
Published in:Fisheries research 2018-03, Vol.199, p.202-211
Main Authors: Leavitt, Jasper S., Huntsberger, Carl J., Smolowitz, Ronald J., Siemann, Liese A.
Format: Article
Language:English
Subjects:
Dredge survey
Essential fish habitat
Scallop access areas
Spatiotemporal distribution
Tweedie model
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Summary:Barndoor skate (Dipturus laevis) is one of the largest skate species in the Northwest Atlantic, and seasonal trawl surveys have identified Georges Bank as critical barndoor skate habitat. We examined fine-scale changes in the seasonal distribution and relative abundance of barndoor skate in the scallop access areas in Closed Area I (CAI) and Closed Area II (CAII) on Georges Bank using catch data from a three-year seasonal scallop dredge survey. Throughout the survey, 2664 barndoor skates were caught and measured, and over 92% of the skates were juveniles. Seasonal changes in skate abundance were documented in both Closed Areas, with catches peaking in August and September. During the summer and fall, skates were caught across all surveyed depths, while catch was limited to deeper waters in the winter and spring. Barndoor skate relative abundance in each Closed Area was modeled using generalized additive mixed models with Tweedie distributions, and the final models, with month, depth, and bottom temperature as fixed effects, effectively explained the spatiotemporal distribution patterns observed in each area. Barndoor skate abundance estimates are based on data collected during the Northeast Fisheries Science Center (NEFSC) spring and fall bottom trawl surveys, and the Essential Fish Habitat (EFH) designations for barndoor skate are currently being reassessed as part of the Omnibus Habitat Amendment 2. Our study strongly supports the recommendation to expand barndoor skate EFH since we observed high numbers of barndoor skate on Georges Bank in the late summer, a season with limited numbers of NEFSC surveys.
ISSN:0165-7836
1872-6763
DOI:10.1016/j.fishres.2017.11.005