Critical Uncertainties: Aquaculture in Ocean Replenishment

SCORE Principle

" If the current trend in advances in aquaculture technology continues as expected, new 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. "

Concerns about stock enhancement are generally classified as genetic, ecological, management, and philosophical in nature. The main issues and critical uncertainties are:

(i) Effects of stock enhancement on ecosystem dynamics

Is there sufficient environmental carrying capacity to support additional production at release sites?
Do hatchery fish add to overall population size or simply replace wild stocks in their habitat?
Can habitat be expanded to incorporate larger numbers of stocked and wild fish?
What are the health effects on wild fish through transmitted disease and parasites?
What are optimal release strategies that maximize survival without impacting wild populations?
What are the key measures of suitable habitat and microhabitat for releases?

(ii) Effects of stock enhancement on wild stock genetics

What is the genetic structure of the population to be enhanced?
Is the genetic structure of released fish representative of the natural population that is to be enhanced?
Are inbreeding & outbreeding depression or domestication selection occurring?
Is translocation of exogenous genes happening?
Can changes in the genetic diversity of wild stocks be prevented?
What is the impact of hatchery-induced genetic change on wild stock genetic fitness?

(iii) Fishery enhancement must be integrated in overall fishery management

When should hatchery releases be used, and what issues need to be resolved before beginning a new hatchery-release program?
What are the goals of stock enhancement?
What are the explicit indicators of success, and how will success be measured?
What determines when to stop stocking? whether to stop stocking?
What other fishery management strategies need to be coupled with stock enhancement?
Do the costs of stock enhancement outweigh the gains? Has economic efficiency been optimized?
Can the same level of enhancement gained from hatchery releases be achieved through stronger fishing regulations and enforcement?

(iv) Philosophical issues

Will fisheries enhancement be viewed as a panacea that can replace other management strategies?
If stock enhancement proves to be successful, how will it be managed, giving due attention to harvest reductions, habitat protection and restoration as viable alternatives? Will it be hard to turn off?
Is marine fisheries enhancement an environmentally viable fishery management tool or simply another case of 'techno-arrogance'?
How does stocking fit into ecosystem management policy?
If successful, will stock enhancement result in loss of funds for other management techniques?

Clearly, a critical science-based evaluation is needed of the potential for stock enhancement to become an effective fishery management tool to help replenish depleted marine fisheries and increase fisheries production. Historical emphasis on release magnitude has overshadowed key questions, like those stated above, about stocking effectiveness and effects on fisheries landings and ecological/genetic impacts to fish populations. The inattention of the scientific community over the past century in applying rigorous scientific inquiry to evaluate and refine stocking effects on fisheries and wild stocks has fueled opposition to marine stock enhancement. Advances in understanding 'enhancement effect' have not kept pace with advances in developing new hatchery technology, and this has resulted in uncontrolled and unevaluated releases and inefficient use of economic resources.

If the current trend in advances in aquaculture technology continues as expected, new 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.

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 more than 100 years of questionable stocking practices before quantitative evaluations of effectiveness began in the 1990s. Lack of consensus on key research issues and failure 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; Leber, 1999, 2002, 2004).

Research collaborations are needed to integrate the principal sub-disciplines in stock-enhancement 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.