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Evaluating Biochemical and Physiological Predictors of Long Term Survival in Released Pacific Blue Marlin tagged with Pop-Up Satellite Archival Transmitters (PSATs)
Reports (PDF): FY 2004
Responsible fisheries management decisions rely on accurate population assessments. These assessments must be structured upon a comprehensive knowledge of the temporal and spatial distribution patterns, and the population sub-structure of Pacific blue marlin. For catch-and-release sports fishing and non-retention of commercially caught billfishes to be justifiable management options, there must be a reasonable likelihood that released fish will survive. At present, there is little basis for the assumption that released Pacific blue marlin have an acceptable level of long term survival. Moreover, there is no scientific basis for making this prediction for any billfish species.
At present, except for a limited short term study by Graves et al (2002), there is little basis for the assumption that released Pacific blue marlin have an acceptable level of long term survival. Once hooked, Pacific blue marlin fight with an intensity and ferocity that leads to profound disruption of biochemical and physiological processes (Wells and Davie 1983). Therefore, even when recreational anglers and commercial fishermen practice good catch and release fishing, high rates of delayed mortality are a distinct possibility. The issue of long term survival of released fish may be especially critical for Pacific blue marlin caught near the main Hawaiian Islands, as this area appears to be a significant spawning area (Hopper 1990).
Project researchers want to better predict the long-term survival of released Pacific blue marlin by establishing biochemical and physiological parameters of caught marlin and affixing Pop-Up Satellite Archival Transmitters (PSATs) so marlin can be tracked after release. Assessing the biochemical and physiological disruption to the fish, and tracking the released fish will allow researchers to, 1) eliminate biochemical parameters that have no bearing on mortality, and 2) provide a subset of parameters found to be good predictors of long term survival. Researchers propose to measure a spectrum of parameters associated with exercise metabolism, tissue damage and oxidative stress.
Sampling will be done on marlin caught using sports fishing gear, commercial longline gear, and scientific longline gear. Blood samples will be collected at sea and stored in separate solutions to stabilize metabolite, protein and RNA levels. PSAT pop-off dates will be set to evaluate long-term survivability (i.e. >200 days). Researchers hope to tag and collect samples for as many as 10 fish per year or more. For fish sampled at sports fishing tournaments, fight time and intensity will be recorded.
There is a general perception that a protracted fight time will reduce the likelihood of survival but there is no scientific basis for this conclusion. Moreover, current fishing tournament practices encourage the release of small (<250 lb) fish, and retention of larger fish. This practice is generally based on the assumption that larger fish do not survive the trauma of capture and release because of the generally protracted fight times. However, as fish over 250 lb caught during the summer near the main Hawaiian Islands are spawning females (Hopper 1990) this practice could have significant biological impact because of possible spawning site fidelity in Pacific blue marlin (Graves 1996). Knowledge of the long-term survival of these large individuals is therefore critical. Researchers hope data from this project will also allow predictions of the effects of non-retention practices in commercial longline fisheries capturing both blue marlin and blue shark.
Year 1 funding for this 2-year project estimated to be available December 2002.
Dr. Michael Musyl
National Marine Fisheries Service
Kewalo Research Facility
1125-B Ala Moana Blvd.
Honolulu, Hawaii 96814 USA
Phone (808) 592-8305
FAX (808) 592-8300
Department of Biology
CANADA K7L 3N6
Phone (613) 545-6157
FAX (613) 545-6617
Dr. Richard Brill
Virginia CMER Program Director
Virginia Institute of Marine Science
Gloucester Point, VA 23062 USA
Phone (804) 684-7773
FAX (808) 592-8300
75-5863 Kuakini Highway
Kailua-Kona, Hawaii 96740 USA
Phone (808) 326-4431 W / 331-1884 H
This page updated August 14, 2006