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Long-Term Deployment of Satellite Tags on Swordfish using the California Harpoon Fleet

Progress reports (PDF): FY 2009, FY 2008, FY 2007, FY 2006

Project Overview
The main objective of this PFRP project is to utilize the local California harpoon fishing fleet in order to deploy satellite tags on approximately 30 swordfish. This project will help researchers determine whether tagging onboard a harpoon fleet vessel is a viable platform for long-term deployment of pop-up archival satellite tags. Project researchers will also field-test two different dart designs and determine the contribution of the pin to premature release. Data results from the tags will provide insight into swordfish movements and habitat use and will further investigate the potential for using environmental variables and dive patterns to augment location estimates. If the method in this pilot effort proves successful, the use of these techniques may be expanded both nationally and internationally - e.g., off of South America and Japan, where there are also harpoon fleets.

Swordfish support an economically important international fishery that landed a record 85,000 metric tons (mt) in 1995, up from 59,000 mt in 1985 (Folsom et al. 1997). Many Pacific Rim countries host active swordfish fisheries, including Chile, Japan, Australia, several of the north Pacific Island nations, and the United States and Mexico (Carocci and Majkowski, 1996). While Pacific populations presently appear to be stable (Uosaki 1998, Hinton and Deriso 1998, M. Hinton pers. com.), it is critical that effective management be implemented to ensure that the Pacific swordfish populations are not over-exploited, as were the populations in the Atlantic.

Comprehensive management, whether focused on single species or at the ecosystem level, requires knowledge of stock structure. Efforts expended to date to define swordfish stock structure in the Pacific have lead scientists to propose that there may be from one to as many as four distinct stocks (Nakano 1998, DeMartini 1999, M. Hinton pers. com.). Unfortunately, lack of scientific data still precludes determining with confidence, which proposed model is most accurate. Research methodologies such as temporal and spatial patterns in catch rates, genetic analysis, and conventional tag and release studies, have failed to provide a complete understanding of stock structure in the Pacific. Genetic data suggest some differentiation around the Pacific basin, but it has not been possible to clearly distinguish between a single and multi-stock structure (Reeb et al. 2000). Consequently, developing a management plan or predicting Pacific-wide population trends becomes considerably more complex. To provide the understanding of Pacific swordfish stock structure necessary for effective management, additional information is essential, and the demonstrated difficulties using traditional techniques mandate a new approach.

While pop-up satellite archival tags (PAT) provide an innovative tool for examining the movement patterns and temperature and depth preferences of many pelagic species (Block et al. 1999, Lutcavage et al. 2000, Arnold and Dewar 2001, Boustany et al. 2001), studies conducted to date with swordfish have returned disappointing results. In the first three studies, fish were captured for tagging using longlines. Problems encountered in these studies included the following (1) non-reporting by the satellite tag, when the tag is deployed but never transmits, (2) fish mortality, when it can be demonstrated using depth data that the fish died shortly after release, and (3) premature release, when the satellite tag releases from the fish prior to the programmed date (Sedberry and Loefer 2001, Brill pers. com., Dewar unpublished data). Premature release and non-reporting can both result from mortality. Sedberry and Loefer (2001) report that 52% of the tags deployed either released early or failed to report. In the study conducted by Brill, the non-reporting rates ranged from 50-70% - half or more of the tags never transmitted information to a satellite. Dewar (unpublished data) found that while all tags deployed from a longliner reported, five out of eight swordfish died shortly following release. These results indicate that a different approach is necessary if the potential of PAT tags are to be realized in studies of swordfish. Tagging swordfish from a longline vessel has proven ineffective and inefficient.

A potential alternative to the use of longline vessels to deploy satellite tags on Pacific swordfish is the harpoon fleet operating out of Southern California. It is, with out doubt, the time on the longline and handling that result in high mortality rates and also likely contribute to the low reporting rates. The ability to harpoon swordfish diminishes the level of stress associated with tagging efforts by eliminating the requirement to catch and handle the fish During the harpooning event the fish are at the surface and often listless, perhaps from spending long periods in cool water, which thereby allows for the actual harpooning event to be relatively controlled. An experienced harpooner can target a small area on the fish for implanting the dart. The location of dart attachment is critical for successful tag deployments. In 2002 and 2003, seven satellite tags were secured to swordfish for short-term deployments using a harpoon (Dewar unpublished data). The goal of this study was to obtain high-resolution data on habitat utilization and the tags were programmed to remain attached for only 6 to 8 weeks. Of the seven tags deployed, two tags never reported, three tags released early, two of which swam below 1500 m (triggering the release mechanism, the RD1500), and the remaining two tags remained attached for the programmed time. While this study indicates the potential for using the California harpoon fleet to deploy satellite tags on swordfish, the sample size is small and additional efforts are required to develop methods to maximize deployment durations and minimize premature release.

The objectives of this project are four-fold:
• First, by working with harpoon fishermen based out of southern California project researchers will determine the potential for using the harpoon fleet to deploy pop-up satellite tags for up to 10 months. Efforts to date have shown some promise, however, the sample size is currently too small to make any meaningful conclusions.
• Second, in an effort to develop methods for long-term attachments, two different dart types will be tested. The first design will be similar to that used by harpooners but smaller and made from nylon. The second dart to be used is the nylon dart developed by Pfleger Institute of Environmental Research.
• Third, the pop-up satellite archival tags will be used to begin to examine reports that two stocks of swordfish mix off California in the summer. Movements will be inferred from the release and pop-up points, at a minimum. The behaviors and habitats encountered will be determined from the temperature and depth data transmitted by the tags.
• Fourth, because the diving behavior masks the light signals at dawn and dusk used to estimate longitude and latitude we will examine the potential for using hydrographic features to estimate locations between tag and pop-up. The goal is to determine the rough geographic regions rather than a highly accurate geolocation, which is unlikely.

Proposed Activities
In the summer and fall of 2004 -2006 project researchers will work with the California harpoon fleet to deploy a total of 30 satellite tags on swordfish off the coast of California, 6 in 2004 and 12 each in 2005 and 2006. Tags will be deployed for periods of 6 and 10 months using two different dart types. If successful, this will provide a method for future researchers to obtain critical information necessary for the management of swordfish in the Pacific, information that has been impossible to obtain using other methods.

Pop-up Satellite Tags
Project researchers will use the PAT4 pop-up satellite archival tag produced by Wildlife Computers of Seattle, WA. These tags are equipped with a number of mechanisms to reduce non-reporting. The incorporation of a RD1800 will sever the leader and release the tag if the fish swims below 1800 m. In addition, a programmed "premature release software" will initiate transmission if the tag releases early and floats to the surface or the fish dies and sinks to the bottom that is shallower than the release depth of the RD1800. The new RD1800, may reduce premature release associated with deep diving behavior and increase deployment durations for swordfish. An additional feature of the PAT4 will help to identify the cause of premature release. The PAT4 determines if the pin is still in place or broken when premature release is initiated, which will help to determine what improvements are necessary.

Tag Deployments
The tags will be deployed using methods and equipment typically used for harpooning swordfish in the waters off California. Deployments will occur between July and November working with two harpoon fishermen, Lance Reinhardt on the F.V. Leslie Anne and Leon Bundy on the F.V. Fin Cat. Both fishermen have been harpooning for over 20 years and assisted H. Dewar in PAT tag deployments in 2003. Working with only two fishermen will reduce the variation in tag deployments.

Tags will be deployed using one of the following two dart types: (1) a nylon dart recently designed at the Pfleger Institute of Environmental Research. This dart was used successfully in previous deployments on swordfish as well as other species such as white sharks and ocean sunfish. To date, only 2 of 15 tags deployed using these darts has released prematurely for reasons other than mortality or the fish traveling below the 1500 m release depth of the RD1500 (Dewar unpublished data). (2) The second dart will incorporate the design of the swordfish irons used in harpooning. However, this dart will be smaller and will be machined out of nylon to reduce weight. The two darts will be distributed randomly among deployments with half used for each of the 6 and 10 month deployments.

Data Analysis
One of the main objectives of this project is to determine the potential for using the California harpoon fleet to deploy satellite tags for periods of 6 to 10 months. The success will be indicated by the incidence of mortality, premature release, pin breakage, and non-reporting. Comparisons of retention rates between the two dart types will indicate which is better suited for long-term tag attachments.

For the data recovered from the tags, efforts will focus on integrating the behavioral and environmental data to determine the influence of physical features on behaviors. The behavioral data will include the maximum and minimum depths and temperatures as well as the percentage time spent in different temperature and depth increments. The environmental data obtained from the tag will include thermal profiles, sea surface temperature and occurrence of fronts as indicated by shifts in sea surface temperature between measurement interval. Polovina has recently developed analytical methods to describe a water columns thermal profile through the duration of the tracks using temperature and depth data collected by the PAT tags.

Additional efforts using the behavioral and environmental data will explore the potential for improving location estimates between tag deployment and pop-up. The objective is not to obtain a precise latitude and longitude, but to determine a general oceanographic region visited by the swordfish. It should, for example, be possible to determine whether swordfish from the eastern Pacific visit waters off Japan or move to the southern hemisphere. The environmental information that will most likely prove useful includes the thermal profile of the water column, the presence and characteristics of fronts, and sea surface temperature.

Year 1 funding for this 3-year project estimated to be available mid-2005.

Arnold. G. and Dewar, H. ( 2001) Electronic Tags in Marine Fisheries Research: A 30-Year Perspective. pp. 7-64. In: J Seibert & J. Nielsen (ed.) Electronic Tagging and Tracking in Marine Fisheries. Kluwer Academic Publishers, Dordrecht, The Netherlands.
• Block, B., Dewar, H., Farwell, C. and Prince, E. (1999) A new satellite technology for tracking movements of Atlantic bluefin tuna. Proc. Natl. Acad. Sci. USA 95: 9384-9389.
• Boustany, A.M., Davis, S.F., Pyle, P., Anderson, S.D. Le Boeuf, B., and Block, B.A. (2002) Satellite tagging - Expanded niche for white sharks. Nature 415: 35-36.
• Carocci, F. and Majkowski, J. (1996) Pacific tunas and billfishes. Atlas of commercial catches. Rome, FAO.
• DeMartini, G.T. (1999) Stock Structure. Proceedings of the second international Pacific swordfish symposium. NOAA-TM-NMFS-SWFSC-263.
• Dinardo, et al., (1999) Proceedings of the second international Pacific swordfish symposium. NOAA-TM-NMFS-SWFSC-263.
• Folsom, W.B., Weidner, D.W. and Wildman, M.R. (1997) World swordfish fisheries: An analysis of swordfish fisheries, market trends, and trade patterns Past-Present-Future. Volume 1. NOAA Tech. Memo. NMFS-F/SPO-23.
• Hinton, M.G. and Deriso, R.B. (1998) Distribution and stock assessment of swordfish, Xiphias gladius, in the eastern Pacific Ocean from catch and effort data standardized on biological and environmental parameters. Proceedings of the International Symposium on Pacific Swordfish, December 10-13, 1994. Ensenada, Mexico. NOAA Technical Report 142. 161-179.
• Lutcavage, M., R. Brill, J. Porter, P. Howey, E. Murray, A. Mendillo, W. Chaprales, M. Genovese, and Rollins, T. (2000) Summary of pop -up satellite tagging of giant blue-fin tuna in the joint US-Canadian program, Gulf of Maine and Canadian Atlantic. ICCAT, SCRS/00/95. 9 pp.
• NMFS (1994-1999) Billfish News Letter. U.S. Nat. Mar. Fish. Serv. SWFCS, La Jolla CA.
• Nakano, H. (1998) Stock status of Pacific swordfish, Xiphias gladius, inferred from CPUE of the Japanese longline fleet standardized using general linear models. Proceedings of the International Symposium on Pacific Swordfish, December 10-13, 1994. Ensenada, Mexico. NOAA Technical Report 142, 195-209.
• Reeb, C., Arcangeli, L. and Block, B. (2000) Structure and migration corridors in Pacific populations of the swordfish, Xiphias gladius, as inferred through analysis of mitochondrial DNA. Marine Biology (in press).
• Sedberry G.R. and Loefer, J.K. (2001) Satellite telemetry tracking of swordfish, Xiphias gladius, off the eastern United States. Marine Biology. 139:355-360.
• Uosaki, K. (1998) Standardized CPUE of north Pacific swordfish, Xiphias gladius, in the Japanese Large-mesh driftnet fishery. Proceedings of the International Symposium on Pacific Swordfish, December 10-13, 1994. Ensenada, Mexico. NOAA Technical Report 142. 125-131.

Project Investigators:
Dr. Heidi Dewar
c/o Inter-American Tropical Tuna Commission (I-ATTC)
8604 La Jolla Shores Drive
La Jolla, CA 92037 USA
Phone (858) 546-7023
FAX (858) 546-7133
email: heidi_dewar@alumni.ucsd.edu

Dr. Jeffrey Polovina
National Marine Fisheries Service
Pacific Islands Fisheries Science Center
Honolulu Lab
2570 Dole Street, Rm. 216
Honolulu, Hawaii 96822 USA
Phone (808) 983-5390
FAX (808) 983-2902
email: jpolovin@honlab.nmfs.hawaii.edu


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This page updated March 24, 2010