Dolphin-Safe Activities and Accomplishments

A dolphin-safe research program was initiated in 1992, the first year that significantly increased funding was allocated by Congress to NMFS specifically to address the tuna-dolphin issue following the major U.S. tuna cannery's decision in April 1990, to buy only "dolphin-safe" tuna. During 1992, NMFS convened a First Research Planning Workshop to evaluate and prioritize proposed tuna-dolphin research. Following that workshop, NMFS developed a strategic plan (DeMaster 1992). The strategic plan describes a comprehensive approach for gathering information on tunas and dolphins in the ETP and on methods of fishing for tunas in the ETP. The plan outlines research objectives for each of three goals.

  1. Develop and evaluate methods of purse-seining that do not involve chasing or encircling dolphins
  2. Develop and evaluate methods of purse-seining that involve chasing but not encircling dolphins
  3. Improve existing methods of purse-seine fishing to reduce dolphin mortalities

Because U.S. fishermen are prohibited from chasing and encircling dolphins, and because the Inter-American Tropical Tuna Commision (IATTC) had alreaady developed a successful dolphin-mortality reduction program, the NMFS research has concentrated on the first two goals. The Dolphin-Safe Research Program efforts to investigate the potential for capturing large yellowfin tuna in the eastern tropical Pacific Ocean without encircling dolphin focused on obtaining definitive answers to a series of three questions. If the answer to any question in the series was "no" then future efforts would be directed elsewhere.

  1. are large yellowfin tuna ever disassociated from dolphins in the ETP?
  2. can unassociated large yellowfin tuna be routinely detected and captured in the ETP?
  3. are unassociated, detectable large yellowfin available in commercially adequate abundance?

Initial projects were selected based on their potential to 1) improve understanding of the behavioral association between yellowfin tuna and dolphins and 2) develop new methods of locating and aggregating sexually mature yellowfin tuna not associated with dolphins. In late 1992, the NMFS funded the four top priority research projects recommended by the planning workshop,

  1. Tuna-Dolphin Tracking: two 30-day charters of a tuna purse-seine vessel to conduct simultaneous tagging and tracking of yellowfin tuna and dolphins
  2. Tuna Oceanography: evaluation of the potential for using environmental predictors of yellowfin tuna abundance, catchability and distribution
  3. Tuna-Dolphin Food Habits: analysis of food-habits of dolphins, tunas, and other upper-trophic-level predators in the ETP.
  4. Lidar: investigation of the feasibility of locating yellowfin tuna not visually associated with dolphins or other surface cues using airborne lidar and also initiated a number of other research investigations.
  5. ETP Seabirds: investigation of the species composition of bird flocks associated with, and without, dolphins in the ETP and on the flight energetics and foraging ecology of predominant species in these flocks
  6. Passive Optical: investigation of the feasibility of locating yellowfin tuna not visually associated with dolphins or other surface cues using non-lidar airborne optical systems (video, multi-spectral, hyper-spectral, etc.)
  7. FADS: Investigation on the potential for Fish Aggregrating Devices to attract large yellowfin tuna.
  8. Solicitation of Ideas: Investigation on the potential for exisiting and new technologies to allow the capture of large yellowfin tuna without associated dolphin mortality.
  9. Tuna Bycatch: investigation of bycatch associated with ETP purse seine fishing (Perkins and Edwards 1994).

A Second Dolphin-Safe Research Planning Workshop was held at the SWFSC on March 14-17, 1994. The workshop's primary objective was development of a research plan to guide activities within NMFS' Dolphin-Safe Research Program during the next 3-5 years, with emphasis on commercially promising detection methods. Workshop participants included technical experts familiar with various detection and capture methods, fishing experts familiar with the ETP tuna purse-seine fishery, and government agency scientists involved in the tuna- dolphin issue including representatives from the U.S. National Marine Fisheries Service, Mexico's Programa Nacional para el Aprovechamiento del Atun y Proteccion de los Delfines, and the InterAmerican Tropical Tuna Commission. Workshop participants were specifically instructed to limit discussions 1) to large yellowfin, 2) to the ETP, 3) to detection methods other than dolphin cues, and 4) to capture methods that do not involve encirclement of dolphins. The specific topics chosen for discussion and evaluation at the workshop included acoustic, optic, and radar/SAR detection methods and pair trawling.

The experts were emphatic that these studies be completed prior to insitu testing or actual system development. Results from both the signal propagation and target strength modeling projects provided the basis for determining which acoustic detection methods have the greatest commercial potential for detecting large yellowfin tuna in the ETP environment, specific to the ETP tuna fishery. The technical experts unanimously recommended two acoustic and one radar projects which we funded in 1995:

  1. modeling of acoustic signal propagation within and below the shallow mixed layer of the ETP to provide preliminary estimates for design parameters (ranges, power, resolution, etc.) (Rees 1996)
  2. determination of acoustic target signatures of large yellowfin tuna to compare with design parameters. (Nero 1996)
  3. investiagation on the potential for enhancing detection of bird flocks, logs, and tuna with radar. (Summers 1995)

During 1996, NMFS conducted a Separation/Attraction Workshop on methods to separate or attract tuna and dolphins (Edwards 1996), estimated tuna bycatch in the ETP associated with the three methods of fishing (Edwards and Perkins 1998), estimated the annual capture rate for dolphins in the ETP associated with the dolphin-fishing method (Perkins and Edwards 1997a; 1997b), and reviewed dolphin-fishery interactions outside the ETP (Donahue and Edwards 1996).

Based upon the promising results from the two acoustic projects funded in 1995, NMFS funded a project to design an acoustic system to detect tuna at distances out to 40 km (Rees 1998), and a second design was obtained through an SK grant during 1997 (Denny et al. 1998). Another Lidar project was also funded through the SK program (Arete Associates Incorporated 1999).

During 1997, NMFS funded studies on the potential impacts of the lasers used in lidar (Zorn et al. 1998, 2000) and potential impacts of low-frequency sound on marine animals (Ketten 1998), and began participation on a joint study of the effects of blast and sound sources on marine mammals (Ketten et al. 1997).

During 1998, NMFS funded a study on large yellowfin swimbladders as acoustic targets (Schaefer and Oliver 1998, 2000), two studies on the potential distance yellowfin tuna may be capable of detecting dolphin sounds (Finneran et al. 1999, 2000; Au and Nachtigall), a study on the hearing ability of yellowfin tuna (Schaefer and Brill), an additional study on laser saftey standards for marine animals (Zorn and Churnside).

The dolphin-safe research program completed three successive research cycles. The first cycle answered affirmatively the initial question of whether large yellowfin tuna are ever unassociated with dolphins in the ETP, and therefore might be available in commercially adequate numbers. The second cycle determined first, that locating such fish should be possible given the physical oceanographic environment of the ETP, and second, that the most appropriate medium to long range detection devices would be acoustic. Local detection could be improved over current methods by using newly developed and developing optical detection technologies (i.e., lidar and enhanced video). During the third (and last) research cycle, the dolphin-safe research program determined the specifications for the optimal acoustic system for locating large unassociated yellowfin tuna in the ETP, and proposed planning for research surveys to determine distribution, abundance, and commercial potential of the resource.

A comprehensive list of references is provided.