Reducing bottom trawl seabed impacts and bycatch in the Eastern Canada offshore Northern shrimp (Pandalus borealis) fishery
The offshore Northern shrimp (Pandalus borealis) fishery in Eastern Canada is currently harvested by factory freezer vessels using bottom trawls. This fishery is a major contributor to the regions’ economy. However bottom trawling typically is associated with negative benthic impacts and bycatch. To...
Main Author: | |
---|---|
Format: | Thesis |
Language: | English |
Published: |
Memorial University of Newfoundland
2022
|
Subjects: | |
Online Access: | https://research.library.mun.ca/15626/ https://research.library.mun.ca/15626/1/thesis.pdf |
id |
ftmemorialuniv:oai:research.library.mun.ca:15626 |
---|---|
record_format |
openpolar |
spelling |
ftmemorialuniv:oai:research.library.mun.ca:15626 2023-10-01T03:58:19+02:00 Reducing bottom trawl seabed impacts and bycatch in the Eastern Canada offshore Northern shrimp (Pandalus borealis) fishery Araya-Schmidt, Tomas 2022-04 application/pdf https://research.library.mun.ca/15626/ https://research.library.mun.ca/15626/1/thesis.pdf en eng Memorial University of Newfoundland https://research.library.mun.ca/15626/1/thesis.pdf Araya-Schmidt, Tomas <https://research.library.mun.ca/view/creator_az/Araya-Schmidt=3ATomas=3A=3A.html> (2022) Reducing bottom trawl seabed impacts and bycatch in the Eastern Canada offshore Northern shrimp (Pandalus borealis) fishery. Doctoral (PhD) thesis, Memorial University of Newfoundland. thesis_license Thesis NonPeerReviewed 2022 ftmemorialuniv 2023-09-03T06:50:22Z The offshore Northern shrimp (Pandalus borealis) fishery in Eastern Canada is currently harvested by factory freezer vessels using bottom trawls. This fishery is a major contributor to the regions’ economy. However bottom trawling typically is associated with negative benthic impacts and bycatch. To address seabed impact, this thesis evaluated the at-sea performance of a traditional roller footgear using underwater cameras. Results showed that footgear sections were rotating at extremely low rates and offered essential information to further develop an innovative footgear with reduced seabed impact. Secondly, an innovative aligned-rolling footgear was designed and evaluated for use in the fishery. I compared traditional and experimental footgears using engineering models and simulated seabeds in a flume tank. Results revealed that the aligned-rolling footgear bottom trawl produced significantly lower warp loads and reduced seabed contact up to 71.5% depending upon seabed penetration depth modelled. Next, I addressed the issue of a recent increase of juvenile redfish (Sebastes spp.) bycatch in the shrimp fishery. This study investigated the effectiveness of 17 and 15 mm bar spacing Nordmøre grids in a twin-trawl configuration against the traditional 22 mm bar spacing grid. Results showed that smaller bar spacing grids resulted in no significant reduction in shrimp catch across all length classes. Conversely, catch of juvenile redfish was significantly reduced with the smaller bar spacing grids. However, the overlap in body/carapace width between redfish and Northern shrimp limits the overall sorting efficiency of the grids, leaving some juvenile redfish still vulnerable to capture. Finally, I investigated the behaviour of juvenile redfish in response to Nordmøre grids. Behaviours were analyzed for 22 mm and 19 mm bar spacing grids. Reducing bar spacing to 19 mm slightly reduced the number of redfish retained (1.83% reduction) and behaviours exhibited by redfish were similar for both grids. The most common ... Thesis northern shrimp Pandalus borealis Memorial University of Newfoundland: Research Repository Canada Nordmøre ENVELOPE(8.500,8.500,63.000,63.000) |
institution |
Open Polar |
collection |
Memorial University of Newfoundland: Research Repository |
op_collection_id |
ftmemorialuniv |
language |
English |
description |
The offshore Northern shrimp (Pandalus borealis) fishery in Eastern Canada is currently harvested by factory freezer vessels using bottom trawls. This fishery is a major contributor to the regions’ economy. However bottom trawling typically is associated with negative benthic impacts and bycatch. To address seabed impact, this thesis evaluated the at-sea performance of a traditional roller footgear using underwater cameras. Results showed that footgear sections were rotating at extremely low rates and offered essential information to further develop an innovative footgear with reduced seabed impact. Secondly, an innovative aligned-rolling footgear was designed and evaluated for use in the fishery. I compared traditional and experimental footgears using engineering models and simulated seabeds in a flume tank. Results revealed that the aligned-rolling footgear bottom trawl produced significantly lower warp loads and reduced seabed contact up to 71.5% depending upon seabed penetration depth modelled. Next, I addressed the issue of a recent increase of juvenile redfish (Sebastes spp.) bycatch in the shrimp fishery. This study investigated the effectiveness of 17 and 15 mm bar spacing Nordmøre grids in a twin-trawl configuration against the traditional 22 mm bar spacing grid. Results showed that smaller bar spacing grids resulted in no significant reduction in shrimp catch across all length classes. Conversely, catch of juvenile redfish was significantly reduced with the smaller bar spacing grids. However, the overlap in body/carapace width between redfish and Northern shrimp limits the overall sorting efficiency of the grids, leaving some juvenile redfish still vulnerable to capture. Finally, I investigated the behaviour of juvenile redfish in response to Nordmøre grids. Behaviours were analyzed for 22 mm and 19 mm bar spacing grids. Reducing bar spacing to 19 mm slightly reduced the number of redfish retained (1.83% reduction) and behaviours exhibited by redfish were similar for both grids. The most common ... |
format |
Thesis |
author |
Araya-Schmidt, Tomas |
spellingShingle |
Araya-Schmidt, Tomas Reducing bottom trawl seabed impacts and bycatch in the Eastern Canada offshore Northern shrimp (Pandalus borealis) fishery |
author_facet |
Araya-Schmidt, Tomas |
author_sort |
Araya-Schmidt, Tomas |
title |
Reducing bottom trawl seabed impacts and bycatch in the Eastern Canada offshore Northern shrimp (Pandalus borealis) fishery |
title_short |
Reducing bottom trawl seabed impacts and bycatch in the Eastern Canada offshore Northern shrimp (Pandalus borealis) fishery |
title_full |
Reducing bottom trawl seabed impacts and bycatch in the Eastern Canada offshore Northern shrimp (Pandalus borealis) fishery |
title_fullStr |
Reducing bottom trawl seabed impacts and bycatch in the Eastern Canada offshore Northern shrimp (Pandalus borealis) fishery |
title_full_unstemmed |
Reducing bottom trawl seabed impacts and bycatch in the Eastern Canada offshore Northern shrimp (Pandalus borealis) fishery |
title_sort |
reducing bottom trawl seabed impacts and bycatch in the eastern canada offshore northern shrimp (pandalus borealis) fishery |
publisher |
Memorial University of Newfoundland |
publishDate |
2022 |
url |
https://research.library.mun.ca/15626/ https://research.library.mun.ca/15626/1/thesis.pdf |
long_lat |
ENVELOPE(8.500,8.500,63.000,63.000) |
geographic |
Canada Nordmøre |
geographic_facet |
Canada Nordmøre |
genre |
northern shrimp Pandalus borealis |
genre_facet |
northern shrimp Pandalus borealis |
op_relation |
https://research.library.mun.ca/15626/1/thesis.pdf Araya-Schmidt, Tomas <https://research.library.mun.ca/view/creator_az/Araya-Schmidt=3ATomas=3A=3A.html> (2022) Reducing bottom trawl seabed impacts and bycatch in the Eastern Canada offshore Northern shrimp (Pandalus borealis) fishery. Doctoral (PhD) thesis, Memorial University of Newfoundland. |
op_rights |
thesis_license |
_version_ |
1778530967571398656 |