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Marine Bycatch

We agree with Scott Norris (“Thinking Like an Ocean,” Fall 2002) that a practical, cooperative approach to the problem of marine bycatch is required and that most technological solutions will come from within the fishing industry itself. As conservation biologists, we can help fishermen to systematically test the most promising ideas to determine their efficacy.

We also agree that it is imperative that an ecosystem approach replace the current focus on single species in the management of marine fisheries. As many populations of upper trophic-level predators disappear from our oceans as a result of overfishing, we simply continue to fish down the food chain. Thus, we find it somewhat incongruous that Norris perpetuates the simplistic question “How much is one dolphin worth?” in which the costs of various fishing methods are compared by the numbers of fishes, turtles, and dolphins taken as bycatch. Surely, from an ecological perspective, we should consider how the bycatch of one, or a hundred, or a thousand animals will affect the demography of that population and its interactions with other ecosystem components. If our goals are to optimize catches and conserve biodiversity, we need to consider the population-level impacts of by-catch, rather than to simply compare numbers. For example, the bycatch of a small number of animals with slow life histories, such as sharks and sea turtles, may have a much greater ecological impact than the removal of much greater numbers of faster-growing, more fecund species such as mahi-mahi and yellowfin tuna.

We disagree that “harvesting organisms in a diversified manner, spreading the impact vertically and horizontally across the food web” is “ecological common sense.” Rather, we believe that fisheries management must take into account the demographic resilience of specific target and nontarget species, and their trophic linkages, to assure sustainability and conserve diversity.

Finally, we note that the incidental capture of some species may have significant demographic effects, even if most of these animals are released alive. Despite a great reduction in the numbers of dolphins observed killed in tuna purse seines over the past few decades, dolphin populations show no clear signs of recovery. A panel of experts, convened last year by the Secretary of Commerce, concluded that the effects of chase and capture in the tuna purse-seine fishery could significantly impede the recovery of these populations, even when no direct mortality was observed.

ANDREW READ

Nicholas School of Environment and Earth Sciences, Duke University Marine Laboratory, Beaufort, North Carolina

CARRIE BROWNSTEIN

Blue Ocean Institute

Amagansett, New York

LARRY CROWDER

Nicholas School of Environment and Earth Sciences, Duke University Marine Laboratory, Beaufort, North Carolina

CARL SAFINA

President, Blue Ocean Institute

Amagansett, New York

Thinking like a lobbyist

“Thinking Like An Ocean” (Fall 2002) reminds us that the health of whole ecosystems, not just the protection of charismatic species such as dolphins and seabirds, is the ultimate goal of conservation. Unfortunately, with regard to the tuna-dolphin issue, author Norris uncritically presents the views of Martin Hall of the Inter-American Tropical Tuna Commission (IATTC). Had the author consulted with other scientists familiar with the issue, he would have heard a different story:

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• The tuna-dolphin problem has not been solved just because the reported dolphin bycatch is low. Dolphin populations are not recovering as expected. Dolphin populations remain depleted, and the number of sets on dolphins remains high.
• Dolphin protection has not caused dolphin sets (with dolphin bycatch) to be replaced by log and school sets (with fish, shark, and turtle bycatch) in any simple manner. The fraction of sets on dolphins is the same today as it was 40 years ago when fishing on dolphins began (about 40 percent). The annual number of dolphin sets has increased, from 4,300 to 9,400 (averages of first 5 years and most recent 5 years; IATTC annual reports).
• hase and capture by the fishery can affect dolphin populations even if all captured dolphins are released alive from the net. Dolphins are chased frequently—on average about 10 times per dolphin per year for the main dolphin stock. This intensity of interaction could significantly affect survival and/or reproduction, an expert panel concluded.
• Dolphin protection began in 1972 with the passage of the U.S. Marine Mammal Protection Act, not in 1990 with dolphin-safe tuna labeling. A 90- percent reduction in dolphin bycatch was achieved by U.S. fishermen before the IATTC began its efforts with the international fleet.
• Quotas on dolphin mortality, embargoes on tuna imported into the U.S., and dolphin-safe labeling have been the driving forces to reduce dolphin bycatch to low levels, not measures initiated by the tuna industry. Quotas and embargoes were necessary because the backdown procedure (and other industry innovations) did not reduce dolphin bycatch to sustainable levels. The fishermen responded to these measures by improving their performance spectacularly. It was only after dolphin by-catch had dropped to low levels by 1992 that the industry adopted voluntary, and later binding, limits on dolphin mortality.
• Dolphin protection measures are not “emotionally-driven, single-species approaches to defining and solving environmental problems.” Conservation efforts often have to concentrate on individual species under threat, as was and still is the case for these dolphins.
• Comparing bycatch by simple numbers of bodies does not measure the ecological costs of different types of purse-seine fishing. A true ecological comparison would include, at a minimum, differences in life history strategies, population sizes, and ecosystem roles. Considering reproductive rates alone, for example, a dolphin giving birth once every 3 years is not “equal” to a tuna producing millions of eggs per year.

Most importantly, we do not have to choose between harming dolphins and harming other species. What is needed are assessments of species taken as bycatch in nondolphin sets, similar to what has been done for dolphins. Then, if purse-seining is shown to threaten billfish, sea turtles, or sharks, we need to work to reduce bycatch in those nondolphin sets. We do not have to trade off protection of one species against that of another.

TIM GERRODETTE

National Oceanic and Atmospheric Administration (NOAA) Fisheries

PAUL K. DAYTON

Scripps Institution of Oceanography

TIMOTHY J. RAGEN

Marine Mammal Commission

GIS-Based Conservation Planning

In 1997, Save-the-Redwoods League (the League) embarked on an ambitious effort to create a strategy to guide its conservation actions. As part of that effort, scientists at the Conservation Biology Institute (CBI), in close collaboration with the League, created a focal areas model recently reviewed in Conservation In Practice (Winter 2003). Although some helpful criticisms were offered, we feel it contained many errors and misinterpretations of its own and generally misrepresented the intention of the work, its stated limitations, and the relationship between the conservation partners.

Models are abstractions of reality and cannot answer all questions at all times. In this case, the Redwood Focal Areas Model was designed to identify subregions (focal areas) within the larger redwood region that showed the most conservation promise for future site-level planning. It was anticipated that field data would be collected and fed back into the model to expand its utility. The model components, assumptions, and limitations were clearly stated in the accompanying technical report (1) and discussed with the League. Although model output is important, the process also introduced staff and board members to the concepts of conservation biology and has made an important contribution to League activities.

The limitations of the model as described by the review were fully acknowledged by the model developers at the time of its creation. These were discussed in either the technical report or in The Redwood Forest (2) by the authors. The notion that these “major pitfalls” were missed during the model building exercise because of some blind allegiance to conservation science principles and that the League was somehow kept in the dark throughout the process is totally false.

For example, the review criticizes the exclusion of logging roads in the model. The decision was made to exclude them because resources were better spent developing a workable framework rather than spending the total budget on one input theme. By necessity, the model was built around the best available region-wide data. The review article also incorrectly claims we showed the City of Watsonville as an “unroaded area.” In fact, the model identified this as an area with moderate to high road densities (? 2.0 km/km2). Overall, this area and watershed ranked “low” in the model.

The review also points out two serious omissions—lack of aquatic considerations and the need for ground truthing. Both of these topics were discussed in The Redwood Forest. In the case of aquatic data, we elected to exclude it from the original model design because data did not exist or was too patchy at the time. We recommended that this deficiency be corrected as soon as possible. Ground truthing was an activity for future site-level planning.

Despite complex equations, impressive flowcharts, and cutting-edge technology, all models blend science with art, and results from models should be used to inform rather than dictate action. When done well, a good model will inform decision making and lead to good conservation outcomes. In the case of the Redwood Focal Areas Model, this was achieved.

RUSKIN K. HARTLEY

Conservation Planner

Save-the-Redwoods League

JAMES STRITTHOLT, PH.D.

Executive Director

Conservation Biology Institute

Literature Cited

1. Strittholt, J.R., G.E. Heilman Jr., and R.F. Noss. 1999. A GIS-Based Model for Assessing Conservation Focal Areas for the Redwood Ecosystem. Conservation Biology Institute, Corvallis, OR.

2. Noss, R.F. et al. 2000. Conservation planning in the redwoods region. In Noss, R.F. ed. The Redwood Forest: History, Ecology, and Conservation of the Coast Redwoods. Island Press, Washington, DC.