The purpose of this research was to explore the impact of finfish bycatch on
the ocean shrimp Pandalus jordani fishery using two methods. One method looked at
the breakage of the shrimp by finfish bycatch in the nets. The other looked at the
impact of bycatch on fishing decisions.
At-sea research found that finfish bycatch contributes to the breakage of ocean
shrimp. However, the impact is small relative to breakage caused by other handling
procedures. Bycatch was measured from each net of a double-rigged shrimp vessel,
where one side employed a Nordmore grate bycatch reduction device (BRD) and the
other served as a control. Shrimp catch was controlled for BRD use and catch day,
and sampled throughout processing to evaluate breakage. At greater than 50%
bycatch there was a significantly higher percentage of broken shrimp in the control
side than in the BRD side for samples taken at the first and third sampling point
(p<0.05). After this point the differences became non-significant. The percent
breakage increased from a mean 2.4% broken before placement in the hold to a mean
18.0% broken in the final product.
The impact of bycatch on fishing decisions was evaluated by distributing an
expanded logbook to volunteer Oregon shrimp vessels in 1998. Logbook questions
addressed the reasons and time involved for running to initial fishing grounds,
relocating overnight, relocating between tows, dumping tows, and modifying gear.
Completed logbooks were collected from 20 vessels representing 263 trips, 1043
fishing days, and 4727 tows. A soft mesh BRD was used at some point by 25% of
vessels on 8.7% of trips and 3.3% of tows. Bycatch did not figure prominently in
reasons given for choice of initial fishing grounds, relocating between fishing days, or
relocating between tows. Bycatch was the main reason cited for dumping tows. In
total, 430 (9%) tows were dumped. The estimated weight of fish and shrimp dumped
equaled 11.3% and 0.3%, respectively, of the landed shrimp catch. Pacific whiting
Merluccius productus caused 81.4% of the tows dumped due to bycatch. Opportunity
costs attributed to bycatch alone were equivalent to net revenue resulting from 12.3
tows or $3,203 per study vessel. At the fleet level, opportunity costs due to dumped
tows totaled 1,227 effort hours, 32.4 trips, or $155,070. This equates to a 4.6% loss in
gross ex-vessel revenue. / Graduation date: 2002
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/29968 |
| Date | 17 October 2001 |
| Creators | Hoover Krutzikowsky, Vicki |
| Contributors | Smith, Courtland |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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