Post on 14-Mar-2021
transcript
Daniel B. Michrowski Terrance J. Quinn, II
University of Alaska, Fairbanks School of Fisheries and Ocean Sciences, Fisheries Division Juneau, AK
Wakefield Fisheries Symposium, May 2014
Background: 5 – “W’s” & How (much)
Methods – briefly
Injury categories
Influential factors
Take home message
Future efforts
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!
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
27 000 mt caught in 2013 • Retention typically ~30%
Longline fleet: >70% of catch
0
20
40
60
80
Pacific cod -
longline
Misc.
flatfishes -
nonpelagic
trawl
Walleye
Pollock -
pelagic trawl
Other -
longline
Other -
nonpelagic
trawl
Catc
h (0
00
’s t
ons)
Target Species - Gear Type Observed skate catch 98-08 (Stevenson and Lewis, 2010)
100% mortality assumed • Precautionary approach
• Evidence of survival
• Previous injuries encountered at ~3%
Accurate fishing mortality rate necessary • Stock assessment
• Quota allocation
No standard handling protocol • Ripped off hook with gaff
• “Crucified”
• “Horned-off” or brush-bar
Careful handling techniques available
www.blueoceantackle.com; www.mustad-autoline.com
Discarded skates
Release method frequencies
45.3%
29.4%
19.2%
6.1%
Ripped
Crucified
Brush-bar
Other
n = 772
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 Fishing -Length -Handling method
-Disc width -Depth
-Weight -Crew member and experience
-Sex
-Species
Removal of one or both jaws
Tears to both sets of gills
Torn body cavity
Critical injury category “Jaws removed”
Torn jaw
musculature
Tear to one set of gills
Body cavity puncture with exposed organs
Extensive scavenger injuries
Deep pectoral tear
Broken jaw(s)
Tear to lower
mouth area and/or esophagus
Gill punctures Body cavity
puncture without organ exposure
Others
All other injuries, including: • Peripheral
punctures and tears
• Punctures to mouth area
• Tears in upper and side mouth areas
Injury category frequencies
14.9%
63.3%
14.7%
7.0%
Minor
Moderate
Severe
Critical
n = 911
Injury score by release method
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Minor Moderate Severe Critical
Other
Brush-Bar
Ripped
Crucifier
n = 772
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
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
Injury categorization enables mortality estimates
Release method key parameter • Avenue to reduce mortality
Other parameters may be influential – significance requires further study
Further analysis of size and species effects • More sampling
Careful vs. Normal handling • Controlled on survey trip
Captive holding
Tagging
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
Questions?