CENTER FOR FISHERIES ENHANCEMENT

Rationale for Stock Enhancement Research

GUIDING PRINCIPLES

Our stock enhancement research is guided by the principles underlying a responsible approach to marine stock enhancement (Blankenship & Leber, 1995). The program has an outreach arm that works directly with government agencies and stakeholders to help integrate these principles into strategic plans. The program’s focus is on basic and applied research designed to resolve critical uncertainties about stocking effects, efficiency and effectiveness, and whether and how stocking can be used as a fishery management tool in marine and estuarine ecosystems.

FISHERIES LINKAGE WITH AQUACULTURE?: RATIONALE FOR GREATER EMPHASIS ON EVALUATING STOCK ENHANCEMENT POTENTIAL (Excerpts from Leber, 1999)

Advances in marine aquaculture, coupled with the global plateau in capture-fisheries landings (New, 1997), have prompted a rapidly expanding, worldwide interest in marine stock enhancement (releasing cultured animals that spawn in seawater to increase fish or invertebrate population size in coastal environments). Although there is much scientific debate about the efficacy of using stock enhancement to replenish fisheries, clear potential has been shown with some salmonids (Coronado & Hilborn, 1998; Masuda & Tsukamoto, 1998), scallops (Honma, 1993), and Hirame flounder (Kitada et al., 1992, Okouchi et al., 1999). If the current trend continues, new marine aquaculture capabilities will likely spawn many new stocking programs, and the debate over stock enhancement will intensify. Until there is a concerted scientific effort to make major progress in developing and testing stock-enhancement theory, we believe that these new programs will fail to meet their expectations.

TECHNICAL CONSTRAINTS TO STOCK ENHANCEMENT

Why, after a century of stocking marine fishes into the wild, is there still so little understanding of the effects and effectiveness of marine stock enhancement? Historically, little emphasis has been placed on understanding the impacts of stocking on fisheries landings. The approach to marine stock-enhancement during most of the 20th century can be characterized as the Production Phase, the period when all of the emphasis and accountability in stocking programs was focused on aquaculture production and release magnitude. This emphasis on production is pervasive, even today, and has overshadowed critical questions about stocking effects on fisheries landings and fish populations. Absence of the technology needed to tag eggs, larvae and fry also contributed to the paucity of information available to assess stocking impact during the production phase of marine stock enhancement.

After decades of stocking without clear indications of impact, the objective of marine fisheries management in the U.S. shifted around the middle of this century from emphasis on stocking to controlling catch rates (Richards & Edwards, 1986, Grimes, 1995). Subsequently, a whole generation of fisheries biologists learned to reject marine stock-enhancement, which had been "exposed" (by lack of evidence of any impact) as a waste of public resources. This period can be characterized as the denial phase of marine stock enhancement. The denial phase fractured fisheries biologists into two camps, one advocating stocking, the other adamantly favoring increased fishing regulations and habitat protection and restoration over stock enhancement. For several decades, funding for marine stock enhancement all but disappeared in the USA. The denial phase curtailed much of the funding for assessment of stock enhancement effect on marine organisms until the advent and relatively recent proliferation of modern tagging technology, which provided a way to track released juveniles, albeit with varying degrees of success (e.g. the binary coded-wire tag; genetic "tags"; otolith marking; chemical marks; and various external tags; Parker et al., 1990; Bergman et al., 1992). Because of the slow pace of research during the denial phase, advances in marine "stock-enhancement effect" have not kept pace with advances in marine aquaculture technology. Thus, we now have the capability to produce many species of marine fish but we lack basic knowledge about how or even whether to use hatchery-reared fish as a resource management tool in marine environments.

Despite the general lack of impact assessment and theoretical development in this field, there has been a recent increase in interest in marine stock enhancement as marine aquaculture capabilities have expanded. Because of the importance of restoring declining fisheries resources, many governments are allocating substantial resources for marine stock enhancement, irrespective of the fact that the field is only at an intermediate stage of development. Given the century-long history of questionable results of marine stock enhancement, is this wise? Is it time to turn resources away from stocking marine species and, instead, focus those resources on improving other fisheries management strategies? The answer is clearly no; turning resources away from stock-enhancement research would be jumping to unfounded conclusions. We should keep a strong emphasis on developing and testing marine stock enhancement because this field is a new science.

See Blankenship and Leber (1995) and Leber (1999, 2004) for a detailed development of this issue and the need for injecting a scientific approach to re-evaluate the role of fish hatcheries in fisheries management.

The goal of stock enhancement research at Mote Marine Laboratory is to overcome impediments to development of a responsible and effective marine stock enhancement technology that can be used (1) to restore depleted marine fish populations, (2) to augment fishery yields, (3) to provide a tool for advancing basic knowledge about wild stocks, and (4) to establish new fisheries in artificial and altered habitats.

APPROACH AND PHILOSOPHY

To develop a sound marine stock-enhancement technology, we must integrate and coordinate research and expertise in several essential sub-disciplines to solve the pressing issues in this field. As a new science, stock-enhancement of marine fishes (that spawn in seawater) is handicapped by 100 years of questionable stocking practices before quantitative evaluations of effectiveness began in the 1990s. Lack of consensus on key research issues and failure, until this decade, to treat marine stock enhancement as a science have constrained advances in this branch of fisheries science. Given this history, and because of rapidly expanding interest worldwide in starting new stock enhancement programs, we must apply a substantial amount of science towards solving several key constraints to responsible application of stock enhancement technology (Blankenship and Leber, 1995); i.e. to develop this field effectively:

 

  1. We must recognize, assess and minimize risks associated with the reduction of genetic diversity, introduction of diseases, and alteration of communities and ecosystems.
  2. We must augment and not subvert conventional fisheries management and habitat-protection efforts.
  3. We must clearly identify enhancement objectives and specify clear measures of success.
  4. We should give high priority to stock enhancement research for restoration of fish populations constrained by inadequate recruitment and over fishing, but emphasize habitat protection and habitat restoration for fish populations constrained by inadequate habitat.
  5. We should seek to understand and optimize the effectiveness of hatchery-release strategies, and learn how release variables affect survival and the cost effectiveness of stock-enhancement programs.
  6. We must identify release impact and determine whether the fish released actually increase abundance or simply displace wild individuals.
  7. We should consider ecological, biological, and life-history requirements of the target species when forming enhancement objectives and tactics, and evaluate the ecological impact of enhancement.
  8. We should prioritize and select target species based on the full spectrum of criteria that should be used to guide the choice of species for enhancement.
  9. We must identify economic and policy guidelines.
  10. We should apply rigorous use of adaptive management principles to improve stock enhancement programs, and confine experimental research to substocks of the target population.

There is an inevitable flaw in the logic of gauging effectiveness of stock enhancement programs by the number of fish released and the number of release sites targeted. That logic says nothing about the effect of enhancement efforts on fish population size. We must balance the desire for a quick-fix solution to fish depletions with knowledge about the causes of depletions and how to replenish stocks effectively and responsibly. Stock enhancement may have a significant role to play in managing our fisheries in the 21st Century, but the scientific evaluation and development of scientific principles in this field is incomplete.

WHAT WILL IT TAKE?

Systematic application of the scientific method is a crucial factor in learning whether and how we can control stock enhancement impact. To develop stock enhancement responsibly, we must advance this field of science. Our goal at Mote Marine Laboratory's Center for Fisheries Enhancement is to attract some of the finest scientific talent and expertise available to increase our understanding of how to sustain fisheries and develop responsible linkages between fisheries and aquaculture.

Florida’s recreational fisheries are increasingly threatened by a dwindling resource, the effects of an expanding population, and periodic winter freezes and bouts of red tide. Will our children and grandchildren be able to experience the quality of fishing that we have long taken for granted? The opportunity is there, as evidenced already by the results of Mote Marine Laboratory’s stock enhancement program. Only through high-caliber research can we continue to advance stock enhancement technology and evaluate its potential as a successful tool for rapidly replenishing depleted fish stocks in coastal ecosystems.

WHAT ARE THE CRITICAL QUESTIONS IN STOCK ENHANCEMENT?

For the field to advance rapidly as a science, consensus is needed about what the central scientific problems are, and Platt’s (1964) "strong inference," coupled with Hilborn and Walters’ (1992) active-adaptive management approach, need to receive greater emphasis in stock-enhancement research programs. The inattention for 100 years to applying rigorous scientific inquiry and evaluating the effects of marine hatchery releases on fishery landings and on the wild stocks "enhanced" has fueled strong opposition to repeating mistakes of the past. Today, hatchery releases without a quantitative basis for evaluating release impact (i.e. without a strong assessment component) must be recognized as imprudent and that approach put to rest (Blankenship and Leber, 1995; Hilborn, 1999).

In the absence of a paradigm in marine stock enhancement, many of the obvious issues seem equally important (Kuhn, 1970). One way to advance this field is to prioritize the key questions and highlight the need to resolve them. Below are some of the key issues that keep surfacing at stock enhancement symposia. Most of these issues are familiar to workers in this field. Most are also considered in more detail in Cowx (1994), Blankenship and Leber (1995), and Munro and Bell (1997). A sample of some of the most basic questions about managing stock enhancement is included as an example of why we must begin to focus much more on developing stock-enhancement theory.

 

Central questions in marine stock enhancement

MANAGEMENT ISSUES:

  1. What are the goals of stock enhancement?
  2. What are explicit indicators of success?
  3. How are the indicators of success measured?
  4. What issues need to be resolved before beginning a hatchery-release program?
  5. When should hatchery releases be used?
  6. What determines when to stop?
  7. What is a "full-scale" program?
  8. What other fishery management strategies need be coupled with stock enhancement?
  9. What protocols are needed to conserve genetics and health of wild stocks?
  10. What hatchery and stocking protocols would increase survival of released fish?
  11. What is a responsible approach to marine stock enhancement
  12. What improvements need to be made to existing approaches?

MAJOR UNCERTAINTIES:

  1. Do hatchery releases contribute to fishery production?
  2. Can the same level of "enhancement" gained from hatchery releases be achieved through stronger fishing regulations and enforcement? Through habitat restoration?
  3. Is there sufficient environmental carrying capacity to support additional production at release sites?
  4. Are released cultured fish displacing wild stocks? Cannibalizing wild stocks?
  5. What measures of environmental carrying capacity can be used to plan release magnitude?
  6. What are the key measures of suitable habitat for releases?
  7. What are the genetic effects on wild stocks from releasing cultured fish?
  8. What are the health effects on wild stocks?
  9. What are the ecological effects of releases of cultured fish?
  10. What are the optimal release strategies?
  11. Do the costs of stock enhancement outweigh the gains?
  12. Are gains made with stock enhancement sustainable?

Clearly research collaborations are needed to integrate the principal sub-disciplines needed to resolve such a wide range of issues. Rapid advances can be made in understanding marine stock enhancement potential by focusing such collaborations on resolving major uncertainties, using a scientific and responsible approach and active-adaptive management.

REFERENCES CITED

Bergman P.K., Haw F., Blankenship H.L. & Buckley R.M. (1992) Perspectives on design, use, and misuse of fish tags. Fisheries (Bethesda, USA), 17(4), 20-24.

Blankenship H.L. & Leber K.M. (1995) A responsible approach to marine stock enhancement. American Fisheries Society Symposium 15:167-175.

Cowx I.G. (1994) Stocking Strategies. Fisheries Management and Ecology 1:15-30.

Coronado, C. and R. Hilborn, (1998) Spatial and temporal factors affecting survival in coho and fall chinook salmon in the Pacific Northwest. Bulletin of Marine Science 62(2):409-425.

Grimes C.B. (1995) Perspective of the AFS marine fish section on uses and effects of cultured fishes in aquatic ecosystems. American Fisheries Society Symposium 15, 593-594.

Hilborn, R. (1999) Confessions of a reformed hatchery basher. Fisheries (Bethesda, USA), 24(5):30-31.

Hilborn R. & Walters C.J. (1992) Quantitative Fisheries Stock Assessment, Chapman and Hall, New York and London. 570 pp.

Honma A. Aquaculture in Japan. Japan FAO Association, Tokyo, 98 p.

Kitada S., Hiramatsu K., & Kishino H. (1992) Effectiveness of a stock enhancement program evaluated by a two-stage sampling survey of commercial landings. Canadian Journal of Fisheries and Aquatic Science. 49, 1573-1582.

Kuhn T.S. (1970) The Structure of Scientific Revolutions, 2nd edition. University of Chicago Press, Ltd., London.

Leber, K. M. (1999) Rationale for an Experimental Approach to Stock Enhancement. In: Stock Enhancement and Sea Ranching, ISBN 0 85238 246 4, July, 1999. Eds: B.R. Howell (UK), E. Moksness (Norway) and T. Svåsand (Norway). Fishing News Books, Blackwell Science ltd.Osney Mead, Oxford.

Leber, K. M. (2004) Marine Stock Enhancement in the USA: Status, trends and needs. Pp 11-24 In Leber, K.M., S. Kitada, T. Svåsand and H.L. Blankenship (eds) Stock Enhancement and Sea Ranching: Developments, Pitfalls and Opportunities. 2nd Edition. Blackwell Scientific Publications, Oxford. 562 pp.

Masuda, R. and K. Tsukamoto (1998) Stock Enhancement in Japan: Review and Perspective. Bulletin of Marine Science 62(2):337-358.

Munro J.L. & Bell J.D. (1997) Enhancement of Marine Fisheries Resources. Reviews in Fisheries Science 5(2):185-222.

New M.B. (1997) Aquaculture and the capture fisheries: balancing the scales. World Aquaculture 28, 11-31.

Okouchi H., Iwamoto A., Tsuzaki T., Fukunaga T., & Kitada S. (1998) Economic returns from hatchery released flounder Paralichthys olivaceus in Miyako Bay - evaluation by a fish market census. In: Stock Enhancement and Sea Ranching, ISBN 0 85238 246 4, July, 1999. Eds: B.R. Howell (UK), E. Moksness (Norway) and T. Svåsand (Norway). Fishing News Books, Blackwell Science ltd.Osney Mead, Oxford.

Parker N.C., Giorgi A.E., Heidinger R.C., Jester D.B., Prince E.D., & Winans G.A. (Eds)(1990) Fish-Marking Techniques. American Fisheries Society Symposium 7. American Fisheries Society, Bethesda, MD, USA. 879 pp.

Platt J. R. (1964) Strong Inference. Science 146:347-353.

Richards W.J. & Edwards R.E. (1986) Stocking to restore or enhance marine fisheries. In R.H. Stroud (ed) Fish Culture in Fisheries Management, p 75-80. American Fisheries Society, Bethesda, MD.