|
|||||
|
|
Reducing interactions between seabirds and trawl fisheries: Responses to foraging patches provided by fish waste batches |
|
| Authors: | Johanna P Pierre Edward R Abraham John Cleal Nathan A Walker |
| Institution: | a Marine Conservation Services, Department of Conservation, PO Box 10-420, Wellington 6143, New Zealand b Dragonfly Ltd., 10 Milne Terrace, Island Bay, Wellington 6023, New Zealand c New Zealand Seafood Industry Council Ltd., Private Bag 24-901, Wellington 6142, New Zealand d Fishing Vessel Management Services Ltd., PO Box 1279, Nelson, New Zealand e WWF-New Zealand, PO Box 6237, Wellington 6141, New Zealand f Ministry of Fisheries, PO Box 1020, Wellington 6001, New Zealand g Sextant Technology Ltd., 116 Wilton Road, Wellington 6012, New Zealand |
| Abstract: | Seabird bycatch in trawl fisheries is driven by the attraction of birds to foraging opportunities, i.e., the discharge of catch processing waste and the contents of trawl nets. The risk of seabird captures increases with seabird abundance and exposure to fishing gear. We investigated (1) how quickly seabirds responded to discharges of trawl catch processing waste and (2) whether decreasing numbers of seabirds attended trawlers during processing waste discharge events as the time interval between these events increased. Waste was retained onboard the vessel for four different holding periods (30 min, 2 h, 4 h, 8 h), one of which was applied each day using a randomised block design. We determined seabird responses to batch discharge events after the prescribed holding periods using the abundance of large (albatrossses and giant petrels Macronectes spp.) and small (all other petrels except cape petrels Daption capense, shearwaters and prions) seabirds in a semi-circle of 40 m radius, centred on the stern of the experimental trawler. Seabird responses reflected the type of discharge released: birds moved from the air to the water, as the amount of food available increased from no discharge, through sump discharge to batch discharge. When discharge occurred, seabird abundance increased faster than could be resolved with the 5 min sampling period. However, abundance decreased more slowly over a 10-15 min period after the discharge event. The number of large seabirds attending the vessel during discharge events decreased significantly when waste was held for 4 h. For small birds, significant decrease occurred after 8 h. Such holding periods emphasise the tenacity of foraging seabirds, although we have not evaluated any long-term habituation to a particular discharge regime. While holding waste for less than 4 h may not reduce seabird attendance during discharge events, holding for shorter intervals can still reduce bycatch risk, e.g., prior to and during net shooting and hauling. |
| Keywords: | Trawl fisheries Seabird bycatch Mitigation Offal New Zealand |
| 本文献已被 ScienceDirect 等数据库收录！ | |