Wakefield Fisheries Symposium, May University of Alaska, Fairbanks School of Fisheries and Ocean Sciences, Fisheries Division Juneau, AK

Transcription

1 Wakefield Fisheries Symposium, May 2014 Daniel B. Michrowski Terrance J. Quinn, II University of Alaska, Fairbanks School of Fisheries and Ocean Sciences, Fisheries Division Juneau, AK

2 Background: 5 W s & How (much) Methods briefly Injury categories Influential factors Take home message Future efforts

3 The following presentation contains graphic images and video of injuries inflicted on skates as a result of fisheries interactions. The individual skates shown here may or may not have survived the determination of which is the whole point of this project!

4 Skates frequently caught and discarded by longline fleet Usually alive with various injuries Skates: k selected, high trophic level predator/scavenger Eastern Bering Sea shelf Year-round since cooperative formed

5 Catch (000 s tons) mt caught in 2013 Retention typically ~30% Longline fleet: >70% of catch Pacific cod - Misc. Walleye Other - Other - longline flatfishes - Pollock - longline nonpelagic nonpelagic pelagic trawl trawl trawl Target Species - Gear Type Observed skate catch (Stevenson and Lewis, 2010)

6 100% mortality assumed Precautionary approach Evidence of survival Previous injuries encountered at ~3% Accurate fishing mortality rate necessary Stock assessment Quota allocation

7 No standard handling protocol Ripped off hook with gaff Crucified Horned-off or brush-bar Careful handling techniques available

8 Discarded skates

9 6.1% 19.2% 45.3% Ripped Crucified n = % Brush-bar Other Release method frequencies

10 Data collection: two commercial vessel trips, National Marine Fisheries Service sablefish survey Random systematic temporal sample frame Collected from rail with pole-net or from fish trough Four discrete injury severity categories Skates ranked according to most severe injury Parameters: Biological -Length -Disc width -Weight -Sex -Species Fishing -Handling method -Depth -Crew member and experience

11 Removal of one or both jaws Tears to both sets of gills Torn body cavity

12 Critical injury category Jaws removed

13 Torn jaw musculature Tear to one set of gills Body cavity puncture with exposed organs Extensive scavenger injuries

14 Deep pectoral tear Broken jaw(s) Tear to lower mouth area and/or esophagus Gill punctures Body cavity puncture without organ exposure Others

15 All other injuries, including: Peripheral punctures and tears Punctures to mouth area Tears in upper and side mouth areas

16 7.0% 14.7% 14.9% 63.3% Minor Moderate Severe Critical n = 911 Injury category frequencies

17 100% 90% 80% 70% 60% 50% 40% 30% 20% Other Brush-Bar Ripped Crucifier 10% 0% n = 772 Minor Moderate Severe Critical Injury score by release method

18 Multi-dimensional contingency tables Tested independence of injury category and: Release method and crew member experience Size and species Sex Depth Data pooled due to low sample sizes

19 Release method and crew experience (p < 0.001, n = 772) Release method and injury score (p < 0.001) Crew experience and release method (p < 0.001) Depth (p = 0.010, n = 772) Size and species (p < 0.001, n = 911) Confounding effects Includes pilot study

20 Injury categorization enables mortality estimates Release method key parameter Avenue to reduce mortality Other parameters may be influential significance requires further study

21 Further analysis of size and species effects More sampling Careful vs. Normal handling Controlled on survey trip Captive holding Tagging

22 Major funding source: Pollock Conservation Cooperative Research Center Additional support: Freezer Longline Coalition Advisor: Terry Quinn Committee members: Gordon Kruse, Jon Heifetz Sablefish survey team, Marine Ecology and Stock Assessment, Auke Bay Laboratories, NMFS Captain and crew of the F/V Ocean Prowler Aleutian Spray Fisheries Captain and crew of the F/V US Liberator All the faculty, staff, and students at SFOS/UAF Family and friends Symposium hosts

23 Questions?