Presented by Jessica Coombs and Melissa Weierick

• -The American purse seine fishery for tuna came about in the eastern Pacific Ocean in the late 1950’s and for the most part replaced the pole-and-line fishery.

• -It had a higher catch rate and a broader range of operation than the pole-and line method (Francis et al. 1992)

• -Major downfall: lead to an unsustainable number of dolphins being killed (Anganuzzi and Buckland, 1994) -several hundreds of thousands per year in the 1960’s

• -Due to public out cry the 1972 Marine Mammal protection act was passed

• -By 1996 the incidental dolphin mortality rate was reduced to 2500 per year and was no longer declining

• -In recent years some sectors of the environmental community pushed the government to ban all fishing of tuna associated with dolphin.

• -Of coarse the alternatives will cause unwanted side effects

• -The purpose of this paper is to compare the alternatives available while allowing the use of the tuna resource and protecting the dolphin and other components of the ecosystem.

Fishery History:

• Main target: Yellowfin, Skipjack, and Bigeye tuna, Yellowfin being preferred most because it brings in the most money at the market.

• Problems with Pole-and-line fishing: used live bait so it was confined to coastal waters because of need to renew bait when depleted

• -catch mostly small fish

• -not very productive in terms of catch per day at sea

• Purse seine fishing: -could stay out at sea longer and go out farther

• -surrounds school of tuna with wall of netting, when circle complete , the cable passing through the bottom is pulled on board, closing the lower part forming a purse.

• -mostly used in canning industry

• Longline fishing: Lines up to 120km long with baited hooks, deployed at different depths depending of the preferred target

• -much lower catch rate than purse seine and take passively

• -used for sashimi and fresh-fish market

• School sets: associated with birds and water disturbance near the surface

• -produces small yellowfin and skipjack tuna mostly are below optimum size in terms of maximum yield per recruit

• Log sets: associated with floating objects, surround the object with net shortly after dawn because the fish underneath leave the object in the morning

• -produces very small yellowfin and skipjack, usually below market minimum requirement

• Dolphin sets: 4-5 speedboats chase down a herd of dolphin for 20-30 minutes and encircle them with a net.

• -large yellowfin are found associated with schools of dolphins for some unknown reason, only the large ones are able to keep up with dolphin.

• -average size of dolphin groups captured is around 400-500 dolphin but up to 1000 is not uncommon

• -catch exclusively large yellowfin

• -Current mortality in the eastern Pacific approx. 1dolphin/70 tons of tuna caught.

Stocks: used as units of management on the grounds that there is genetic diversity in the units that must be conserved and population dynamics could differ.

Acts to help:

• 1972 Marine Mammal Protection Act

• -mandatory observer program with the US NMFS in charge

• -count the number of dolphin killed and the cause of death, and observe abundance of stock

• 1976 IATTC (Inter-American Tropical Tuna Commission

• -due to other nations taking part

• -want to maintain a high level of tuna production and while maintaining dolphin stocks at or above levels that assure survival and to avoid needless killing of dolphin.

• 1992 International dolphin conservation program

• -signed by representatives of nations participating in purse seine fishery

• -set overall annual limits per vessel and these limits would decline every year from 1993-1999 (Anon., 1993a). –if limit reached then have to stop setting on dolphin for rest of year

• 1996 Declaration of Panama -added to conservation program

• -accelerate schedule to reduce dolphin mortality –introduce stock-by-stock limits

• -address bycatches of other species

• Database -began by observers from IATTC

• -1980’s coverage of US fleets close to 33%, other fleets less than 6%

• -1986 Mexico, with the largest fleet operating in the area, joined

• -1988 non-US fleet coverage was 35%

• -data gathered may be affected by "observer affects"-interferences from intimidation, corruption, obstruction, etc. (Wahlen and Smith, 1985)

Estimates of dolphin abundance: done by research and tuna vessels and aerial surveys

Technical developments to reduce dolphin mortality: -mostly originated by fishers

• -backdown procedure- putting the vessel in reverse after encircling which forces the corkline to sink, allowing the dolphin to escape

• -Medina panel- area of smaller mesh in area of net the dolphins are more in contact with to prevent entanglement

• -raft and hand rescue

• -IATTC with scientists and technicians make sure all vessels have technology and training needed

• -environmental factors- strong subsurface currents

• -behavioral factors- some cooperate with rescue efforts others don’t

• -gear factors- nets not aligned properly, holes in webbing, lack of dolphin saving equipment

• -crew factors- new, unskilled, or poorly motivated captains or crew

• -In 1986 close to 40% of the sets on dolphin had zero mortality

• -1996 88% did

• -Average mortality of dolphin per set decreased from over 12 to 0.33 during the same period

Ecological issues: Impacts of Dolphin mortality on their population

• -To find this we need data on the size of population, trends in abundance, rates of recruitment "reproduction in excess of mortality for a population as a whole" (Perrin and Reilly, 1984), and natural mortality –no reliable recruitment rate data is available so use 2% as default (Smith, 1983)

• -1986-90 NMFS collected data by using a line-transect method in the Eastern Pacific

• -All stocks involved in fisheries have population sizes >400,000 –seems to be no danger of extinction for any of them, at least from impact of fisheries

• -PBR "potential biological removal" formula to determine safe level of take

Ecological impacts of fishing: Need an ecologically sound way to utilize the tuna resource, do this by:

• high yield per recruit ratio -optimum size for yellowfin 110-120cm get these from dolphin sets, school sets produces mostly below optimum size

• minimize lose of genetic diversity –most caught in log or school sets are not sexually mature

• minimize discards –log sets discard 20%, school sets 2% b/c below market min, requirement

• minimize energy use by vessel

• minimize pollution –air pollution (burning fuel) higher from dolphin sets than log –water pollution from dumping fuel (do so when make big catch shortly after leaving port –marine debris amount unknown

• minimize lost and discarded gear –seldom happens, when does it sinks to the bottom

• minimize bycatch –Log sets produce most bycatch, dolphin sets the least

• keep "subsidies" to other species at a minimum –ex. May tilt the competitive equilibrium among species –this impact is hard to quantify, we also don’t know the effects of selective removal

Alternatives:

• Stay in area, set on logs an schools: –reduces subsequent bycatches by reducing abundance of many species b/c of high bycatch –less bycatch with school sets than log –more likely to replace dolphin sets with log sets (anon. 1997) –can only add so many artificial logs before reach saturation level

• -average log set: 36 tons of tuna, 9 of which are yellowfin, mostly skipjack –can only make 1 set per day

• -average dolphin set: 18 tons, all yellowfin: several sets per day

• move to other oceans and fish on school or logs: -not good solution –original area would be underutilized –most stocks on other areas already fully exploited –bycatches would still occur

• change gear and stay in same region:

• ~Switch to pole-and-line fishing -limited to coastal waters –deplete bait species (Bailey, 1996) –not sufficient catch for fuel used –no dolphin bycatch, other minimal –can’t supply the need by the canning industry

• ~Switch to longlines –total catch much lower than purse seine –bycatch sharks, billfish, sea turtles, and others –not optimum size tuna

• ~Switch to gill nets –unlikely to be more selective than purse seine –catch close to 1 dolphin per 4 tons of tuna (w/ lowest mortality estimate) –UN banned their use at high seas

• 4. Remain in area and develop new technology: -find new ways to locate schools of large yellowfin not associated w/ dolphin such as laser, acoustics, radar, etc in early experimental stage

• -find ways to attract large yellowfin, been using FAD’s (fish attracting devices) i.e. artificial logs deployed in areas when and where large tuna were caught w/ school and log sets before, fishermen using this method in eastern Atlantic implemented a voluntary ban, must be bad

• -find ways to separate tuna from dolphin before chase, needs more experimentation and knowledge about social structure and schooling behavior

• -mid-water trawls, produces more dolphin bycatch than purse seine

Conclusion: To eliminate ecological impacts by a fishery is impossible but we can work to mitigate them. The approach needs to be an international one, based on science and on the education of the fishers to produce needed changes.

Anganuzzi, A.A. and Buckland, S. (1994) Relative abundance of dolphin associated with tuna in the eastern Pacific Ocean: analysis of 1992 data. Rep. Int. Whal. Comm. 44, 361-366.

Anonymous (1993a) Inter-Am. Trop. Tuna Comm. Ann. Rpt for 1992. 315 pp.

Anonymous (1997) Inter-Am. Trop. Tuna Comm. Ann. Rpt for 1995. 334 pp.

Bailey, K., Williams, P.G. and Itano, D. (1996) By-catch and discards in western Pacific tuna fisheries: A review of SPC data holdings and literature. Noumea, New Caledonia: Oceanic Fisheries Programme, South Pacific Commission, Tech. Rept 34.

Francis, R.C., Awbrey, F.T., Goudey, C.A., Hall, M.A., King, D.M., Medina, H., Norris, K.S., Orbach, M.K., Payne, R., and Pikitch, E. (1992) Dolphins and the tuna industry. Washington, DC: National Academy Press, 176 pp.

Perrin, W.F. and Reilly, S.B. (1984) Reproductive parameters of dolphins and small whales of the family Delphinidae. Rep. Int. Whal. Comm., Special Issue 6, 97-133.

Smith, T.D. (1983) Changes in the size of three dolphin (Stenella spp.) populations in the eastern tropical Pacific. Fish. Bull. US. 81, 1-13.

Wahlen, B.E. and Smith, T.D. (1985) Observer effect on incidental dolphin mortality in the eastern tropical Pacific tuna fishery. Fish. Bull. U.S. 83, 521-530.

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