Length and sex effects on the spatial structure of catches of Pacific halibut (Hippoglossus stenolepis) on longline gear

Loher, Timothy and Hobden, Jessica C. (2012) Length and sex effects on the spatial structure of catches of Pacific halibut (Hippoglossus stenolepis) on longline gear. Fishery Bulletin, 110(1), pp. 46-51.

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Abstract

Field experiments were conducted to test the hypotheses that Pacific halibut (Hippoglossus stenolepis) display small-scale spatial structure within longline catches, relative to other species and empty hooks, or within-species based on sex or length. Sequential hook-by-hook inventories, along with length and sex data, were taken at thirty-one survey stations. Two-dimensional spatial statistics were used to test for 1) aggregation, defined as the clustering of individuals within a given demographic of size or sex over small intervals of distance; and 2) segregation, defined as the sequential occurrence of individuals within a given demographic of size or sex, uninterrupted by other observations, irrespective of the distance between individuals. Statistically significant structure was detected within catches that is more commonly associated with fish length than sex. Significant spatial structuring occurred at 60% of all stations tested. Significant aggregation of halibut of legal length for commercial retention (≥82 cm) was detected at 44% of stations and aggregation of sublegal-size halibut was detected at 11%. Maleand female-based aggregations were observed at 22% and 11% of stations, respectively. Significant segregation of females was observed at 20% of stations, male segregation occurred at 8% of stations, and segregation by size at 16% of stations. Understanding small-scale spatial structure within longline catches may help us interpret changes in survey and commercial catch data. If structure is generated by behavior, then observed size-at-age or relative sex-ratios may be biased relative to underlying distributions. Although physical processes such as gape limitation should remain stable over the time, dynamic processes may be spatially and temporally variabl

Item Type: Article
Title: Length and sex effects on the spatial structure of catches of Pacific halibut (Hippoglossus stenolepis) on longline gear
Personal Creator/Author:
CreatorsEmail
Loher, Timothy
Hobden, Jessica C.
Refereed: Yes
Journal or Publication Title: Fishery Bulletin
Volume: 110
Number: 1
Page Range: pp. 46-51
Date: January 2012
ISSN: 0090-0656
Issuing Agency: United States National Marine Fisheries Service
Subjects: Biology
Ecology
Fisheries
Item ID: 8689
Depositing User: Patti M. Marraro
Date Deposited: 07 Jun 2012 14:48
Last Modified: 07 Jun 2012 14:48
URI: http://aquaticcommons.org/id/eprint/8689

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