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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)

Related PFRP projects:
Developing Biochemical and Physiological Predictors of Long Term Survival in Released Blue Sharks and Sea Turtles

Pop-Off Satellite Archival Tags to Chronicle the Survival and Movements of Blue Sharks Following Release from Longline Gear

Modeling the Eco-physiology of Pelagic Fishes and Sharks with Archival and Pop-up Satellite Archival Tags (PSATs)

Progress Reports (PDF): FY 2004 , FY 2003

PROJECT OVERVIEW
Pacific blue marlin are an emerging fisheries management issue in Hawaii. Not only is there a continuing significant commercial harvest, but blue marlin are also specifically targeted by a large recreational and charter boat fleet. The latter two form the basis of an extensive and expanding "fishing tournament industry" whose economic impact is significant and whose influence on Hawaii tourism extends worldwide.

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.

Determinants of survival upon release
Energy metabolism - conduct plasma metabolite analysis to see if released fish reestablish sufficient hormonal and metabolic homeostasis.
Tissue damage - to determine the extent of muscle and protein damage from burst energy.
Stress proteins - to determine extent of protein damage by examining production rates of heat shock protein mRNA and protein levels that occur after exhaustive exercise.

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.

Footnotes:
• Graves, J.E. Conservation genetics of fishes in the pelagic marine realm. In: Conservation Genetics. Case histories from nature. J.C. Avise and J.L. Hamrick, eds. Pp. 335-336. Chapman & Hall, 1996.
• Graves, J.E., B.E. Luckhurst, and E.D. Prince. 2002. An evaluation of pop-up satellite tags for estimating postrelease survival of blue marlin (Makaira nigricans) from a recreational fishery. Fishery Bulletin, 100: 134-142.
• Hopper, C.N. Patterns of Pacific blue marlin reproduction in Hawaiian waters. In: Planning the Future of Billfishes. Research and Management in the 90s and Beyond. Proceedings of the Second International Billfish Symposium. Marine Recreational Fisheries #13. National Coalition for Marine Conservation Inc. 1990.
• Wells, R.M.G. and P.S. Davie. Oxygen binding by the blood and hematological effects of capture stress in two big game fish: Mako shark and striped marlin. Comp. Biochem. Physiol. 81A: 643-646. 1983.

This page updated August 14, 2006