Improve stock assessments of Pacific billfish by increasing baseline data on movements, growth, reproduction, and tagging mortality through a research collaboration between Pacific recreational billfish anglers, Mexican fishery scientists, and the Southwest Fisheries Science Center (SWFSC).
Pacific billfish will soon be managed under a west coast fishery management plan (FMP) and under an international treaty. On the west coast of the US, a FMP is being developed by the Pacific Fishery Management Council for highly migratory species (tunas, billfish, and sharks). Starting in 2000, stocks will also be managed over a vast area of the Pacific (excluding exclusive economic zones) under an international convention. While these changes in policy make possible effective management of Pacific billfishes, the lack of baseline data on these stocks makes management both difficult and risky. In short, not enough data exist for adequate stock assessments on most species.
The SWFSC for the last 35 years has carried out an angler-based tagging program on marlins, sailfish, and swordfish; and conducted an annual mail census of fishing effort in the Pacific. Interest in angler-based programs has intensified greatly in recent years, with reported angler fishing days for Pacific billfish increasing from about 6,000 days in 1996 to 11,500 days in 1997, and tagging has expanded throughout the Pacific. With the increasing interest in tag and release programs and increasing information needs for the 2000's, now is the time to strengthen and broaden the SWFSC cooperative billfish program.
Baseline data on age structure, growth, genetic structure, reproduction, habitat characteristics and indices of abundance are needed for improved stock assessments. The tagging data program needs to be strengthened by determining post-release mortality and the effects of hooking injury, tackle weight, and other tagging trauma. All of these data would feed into an assessment of the status of billfish stocks in the Pacific. A thorough assessment of the Pacific Istiophorid stock(s) has not been done since the study of Skillman (1989).
This plan is based on the ideas and concepts developed during a workshop convened by the SWFSC and held at the Balboa Angling Club of Southern California, Newport Beach California, August 11, 1999. This first PacFAAB meeting, hosted by the Balboa Angling Club and United Anglers of Southern California, was attended by SWFSC and Southwest Region staff, representatives from 9 southern California angling clubs, various non government organizations and angling related businesses (see Workshop Participants).
3. Science Approach and Incentives
A salient feature of this plan is that it depends upon a partnership between 2,500 anglers who regularly participate in the current SWFSC Pacific billfish program, their regional and international fishing organizations, the U.S. government (SWFSC), and the Mexican federal fisheries agency Instituto Nacional de la Pesca (INP). The sustained cooperation of anglers and their organizations is vital to the success of this plan because they shall provide the research platforms for collecting data, tagging the fish, logging the observations, and obtaining the biological samples. The scientific approach builds upon the successful billfish tag and release approach thereby supporting the strong conservation ethic inherent in recreational billfish tagging programs. The INP is an important partner because the billfish populations are shared with Mexico and INP is strongly interested in cooperation in billfish stock assessment.
In this plan, anglers shall tag and release billfish and participate in billfish tournaments as before, but in a way that will greatly increase the kinds and quality of scientific information derived from their fishing trips. Guided by SWFSC and Mexican fishery scientists, billfish anglers shall add to and improve the kinds of information obtained from tagged and released fish by measuring fish size and by taking tissue biopsies that provide measures of stress, age, growth, reproductive states, sex, and genetic structure. In addition, tournaments and other fishing records shall be improved to include measures of fishing effort as well as catch, and thereby provide indices of abundance. Special billfish tournaments having fishery objectives as well as fishing objectives shall also be considered.
3.1 Enhancement of the tag and release program
The measurements itemized below are to be implemented by PacFAAB as an enhancement of the tag and release program. These measurements contribute directly to the understanding of vital billfish population rates and also contribute to better management by enhancing our knowledge of billfish movements. The present tag and release program illustrates the extensive movements of billfish throughout the Pacific, and hints that some patterns may be repeated annually. However, further advances require the delivery of more information per tagged animal. This information includes the biological traits of the tagged animal (sex, size, age, reproductive state), the likelihood that the tagged animal will survive (stress level, fishing method, etc.) and the immediate and long-term movement patterns of the animal (archival tags).
Fish size. Movements of fishes often vary with life stage, hence fish size is an essential ingredient for interpreting movements and a critical missing element of the present tag and release program. Two approaches will be used, a three length class classification system implemented using a marked line and a precise method based on a digital camera equipped with laser markers. The latter is the preferred approach once the equipment is developed and calibrated (points on the body from which such measurements could easily be recorded on film would be calibrated against standard measurements of body length and weight).
Sex. Fish sex is essential for interpreting movements and assessing reproductive effort of tagged and released fish. Sex can be determined by applying molecular methods to a tissue biopsy. A tag application device that also provides a tissue biopsy shall be used.
Age. Age determination in billfish is fraught with analytical problems, and obtaining suitable spines for analysis in a tag and release program may be a formidable barrier. On the other hand, use of age-based assessment models would be a major advance in billfish stock assessment. Thus, age determination shall be included initially as a pilot study to determine the extent such measurements might be practical in PacFAAB.
Stress level. The effectiveness of an angler-based tag and release program depends upon the condition of the animals at the time of release and the likelihood that they will survive. That only about 1% of tagged fish are recaptured indicates that some problems may exist. Two approaches are needed: 1) an analysis of the ways that different fishing processes, such as heavy vs. light tackle, affect the condition or stress level of the animal, and 2) an independent assessment of the survival rate using pop-up satellite tags. Stress level and metabolic state can be assessed using chemical analysis of tissue biopsies.
Reproductive activity. When and where billfish reproduce is poorly understood yet essential management information. For example, age and size at first maturity drives all estimates of stock productivity. While obtaining freshly preserved gonads of animals with active ovaries is extremely valuable, some important information can also be obtained from a tissue biopsy. The level of the precursor to yolk in the blood clearly identifies the fish as reproductively active as well as hormones.
Growth potential. Rates of somatic growth is essential baseline information for any stock assessment, yet it is poorly known in billfish. While analysis of skeletal hard parts of fishes (spines, otoliths) shall be studied in this project, age determination is difficult and uncertain and in need of supplementation by other information sources. It is practical to use enzyme-based bioassays from a tissue biopsy to estimate recent rates of somatic growth. Such information would be extremely useful as a supplement to skeletal based rates or as a way of validating them, thereby increasing their accuracy.
3.2 Advanced Tagging Methodologies
Application of pop-up satellite tags is becoming widespread throughout the world for highly migratory species because the approach guarantees a recovery and in the archival version records movements and environmental information. The potential value of such information for fishery management is without question. Barriers to full implementation by PacFAAB are the risk of tag loss due to inexperience of anglers, the need for development of movement models to interpret the data in a way that would be useful for management of billfish stocks, and the unit cost of the tags (from $2,900 to $4,900 US dollars in 1999). While the first two barriers can be overcome by training and acquiring scientific personnel, the unit cost of the tag is a constraint for an angler-based program such as PacFAAB. A solution posed by participants in the first PacFAAB workshop was to consider adding satellite pop-up tagging to billfish tournaments. All participating boats would be equipped with tags, fishermen trained in their application, and PacFAAB would be reimbursed by tournament fees for the expected number of tags used in the tournament. PacFAAB would post the tracks of the fish on the PacFAAB web site, and identify successful fisherman and participants.
3.3 Indices of abundance
Perhaps the most valuable measurements for a stock assessment, other than the fishery landings, are abundance index time series. Since each index suffers from its own biases and imprecision, the more of these one has for an assessment the better. Even the crudest abundance index tracked for enough years is valuable. Billfish tournaments and other billfish fishing provide an opportunity to begin such time series if fishing effort data are recorded along with the catch. As club records from southern California may extend back in time for decades, it is important that such records be rescued and entered into a fishery data base and a crude index of abundance developed. In some regions, mandatory or voluntary bridge logs are maintained by recreational fishermen, but none are used in southern California or Mexico. Thus, an important first step for PacFAAB shall be to enter all data from clubs with longtime series to develop indices of abundance, to begin a voluntary log book program, and to improve tournament data recording so that future records will include a precise measure of catch and effort.
3.4 Direct Biological Measurements from Whole Specimens
Because we strongly support the conservation merit of tag and release recreational fishing, the principal focus of PacFAAB is on non-destructive sources of information from tagged and released billfishes. On the other hand, certain critical measurements exist which can only be obtained by destructive means. These include: collecting a variety of skeletal parts for age determination, assessment of the annual reproductive output of the stock through detailed histological analysis of gonads and fecundity determinations, calibrating shipboard indices of total length, and validating the non-destructive (biopsy) measures of physiological state and age. Therefore, the PacFAAB program shall require the collection of such material and measurements from some fishing tournaments. Cooperation with anglers to provide access to specimens would be needed but data collection would be more conventional as SWFSC staff would be used. A key role could be played by the clubs in the initiation of tournaments with the objectives of obtaining whole specimens for certain kinds of measurements for which a shortage exists. This is now the case for assessment of reproductive rates where freshly preserved active gonads are needed.
3.5 Data Synthesis and Support for Stock Assessment
A critical step in delivering this information to stock assessment specialists and mangers is that it must be analyzed and summarized into a form that would be useful for stock assessment models. These synthetic activities are a vital function of PacFAAB. Synthetic analyses to be included in PacFAAB include: develop a new synthesis of billfish tagging and genetics data to establish movement patterns and identify stock units; develop abundance indices from bridge logbook and tournament data; develop indices of abundance from historic club records; develop an algorithm for converting from a shipboard measurement of a portion of a fish to a whole body measurement and estimate statistical precision; incorporate mitotic growth data with skeletal part increments to improve precision of age determination; and others.
4. Communication and Angler Incentives
The key to the success of the angler-based data collection system of PacFAAB is communication. The primary incentive for anglers to continue their support is the understanding that the results will be made available to them and used effectively in the management of billfish stocks. The annual Pacific billfish tagging newsletter, which gives tag and release information for the year, has supported the communication objectives of the existing program for many years. However, a new level of communication is needed if PacFAAB is to develop into the extensive information gathering cooperative described in this plan. To insure that all collected information is available to anglers, we propose to post such information on a PacFAAB Web site specifically designed for PacFAAB. This will include abundance indices based on input from anglers, records of tag recoveries, PacFAAB research updates, the year's tag and release data, and other features. As a contribution to the development of PacFAAB, and in response to suggestions of anglers at the first PacFAAB meeting, a PacFAAB Web site is currently being developed. If PacFAAB fails to become an extensive data gathering organization, it will not be practical for SWFSC to maintain the site.
If PacFAAB were developed, a steering committee would be formed with representatives from the SWFSC, southern California recreational billfishing anglers and supporting industry, and INP, Mexico. The committee would meet regularly, steer the development of the program, and guide information collecting activities.
5. Partnership with Mexico
A partnership with Mexican colleagues is essential to PacFAAB as eastern Pacific billfish stocks are transboundary and taken in the recreational and commercial fisheries of both Mexico and the US. PacFAAB would coordinate with the INP through the MEXUS-Pacifico forum to identify research associates to participate in joint research activities. Several research areas important to PacFAAB include but are not limited to the following:
a. rescue of historical billfish catch data from sportfishing fleets, fishing resorts, and tournaments conducted in Baja California Sur, Mexico,
b. examine literature in local universities for unpublished life history studies of billfish,
c. define the economic influence of sportfishing for billfish versus recreational fishing for non-billfish species, and
d. monitor commercial fisheries that target billfish.
6. Budgetary Considerations
Southern California anglers and the SWFSC, as a measure of their good faith in the future of PacFAAB, are implementing some of the most basic and lower cost elements described in this plan (as of September 1999). These include: implementation of a bridge log system by anglers; rescue by club and SWFSC representatives of club angling records, and the entry of this information by SWFSC in a data base; collection of tissue samples by anglers for archiving by SWFSC; and development by the SWFSC of a PacFAAB Web site where the data obtained from these cooperative activities will be displayed.
The SWFSC does not have the funds to advance the billfish work to the new level as advocated by this plan, and some doubt exists that even the present level (annual billfishing newsletter, management of the tag and release data base, the postcard billfish angler survey, and distribution of tagging kits) can be continued indefinitely because of competing requirements for baseline data and stock assessments for many other pelagic and groundfishes. In short, additional financial support is required for PacFAAB to become a reality. Funds are needed for chemical and genetics analysis to work with anglers in developing the special equipment needed for measurements on tag and released animals, to coordinate sampling in Mexico and the US and, importantly, to analyze and transform the data so that it will find immediate use in billfish stock assessment and management.