Responsible Approach to Marine Stock Enhancement

The modern generation of marine fisheries enhancement scientists is cultivating an integrative, quantitative and careful approach for developing and managing effective hatchery-based fisheries enhancements. The concepts were originally envisioned by an International Working Group on Stock Enhancement, formed in Torremolinos Spain in 1993, and published in 1995 as a platform paper by two members of the Working Group (who later formed SCORE to help foster and refine this approach). The Working Group, origin and expansion of these ideas are discussed in Leber, 2013.

These concepts are presented in two publications:

  • "A Responsible Approach to Marine Stock Enhancement"   

        (Blankenship and Leber, 1995)pdf file  >>read now.

  • "Responsible Approach to Marine Stock Enhancement: An Update"  

        (Lorenzen, Leber and Blankenship, 2010). pdf file  >>read now.


The ten principles for developing, evaluating, and managing marine stock enhancement programs set out in Blankenship and Leber (1995, see list below) have gained widespread acceptance (Sass and Allen, 2014) as a 'Responsible Approach' to stocking, with basic recommendations for how to make stocking work effectively (and see Cowx, 1994, which emphasizes decision making frameworks for stocking). The 'Responsible Approach' has been widely cited and has provided a key conceptual framework for several subsequent publications (e.g., Munro and Bell, 1997; Hilborn, 1999, Bell et al., 2005, 2006, 2008; Taylor et al., 2005; Zohar et al., 2008). More importantly, it has been used to help guide hatchery development and reform processes in Australia (Taylor et al., 2005; Gardner and Van Putten, 2008; Potter et al., 2008; Taylor and Suthers, 2008), Denmark (Støttrup et al., 2008), Japan (Kitada, 1999; Kuwada et al., 2000, 2004), New Caledonia (Purcell and Simutoga, 2008), Phillipines (Le Vay et al., 2008), and the USA (e.g., Leber, 2004), particularly in California (Bartley et al., 1995; Hervas et al., 2010), Hawaii (Leber et al., 1996, 1997, 1998; Friedlander and Ziemann, 2003), Maryland (Zohar et al., 2008), Mississippi (Blaylock et al., 2000), New Hampshire (Fairchild et al., 2005), North Carolina (Eggleson et al, 2008), South Carolina (Smith et al., 2003; Jenkins et al., 2004), Texas (Karlsson et al., 2008), and Washington (Mobrand et al., 2005). At the same time, there has been a rapid increase in peer-reviewed literature on effects and effectiveness of stocking.


The 10 principles in the original 'responsible approach' (Blankenship & Leber, 1995):

  1. prioritize and select target species for enhancement by applying criteria for species selection; once selected, assess reasons for decline of the wild population
  2. develop a management plan that identifies how stock enhancement fits with the regional plan for managing stocks
  3. define quantitative measures of success
  4. use genetic resource management to avoid deleterious genetic effects on wild stocks
  5. implement a disease and health management plan
  6. consider ecological, biological & life-history patterns in forming enhancement objectives and tactics; seek to understand behavioral, biological and ecological requirements of released and wild fish
  7. identify released hatchery fish and assess stocking effects on fishery and on wild stock abundance
  8. use an empirical process for defining optimal release strategies
  9. identify economic objectives and policy guidelines, and educate stakeholders about the need for a responsible approach and the time frame required to develop a successful enhancement program
  10. use adaptive management to refine production and stocking plans and to control the effectiveness of stocking


Fisheries science and management in general, and many aspects of fisheries enhancement, have developed rapidly since the 'responsible approach' was first formulated. These developments made it necessary to revise the 'responsible approach' to take into account, in particular, the paradigm shift towards analyzing and managing enhancements from a fisheries management perspective. The developments also provided the tools for implementing the shift.


Most enhancements remain weak in four particular areas (Lorenzen et al., 2010):

  1. Fishery stock assessments and modelling are integral to exploring the potential contribution of stocking to fisheries management goals; yet both are found lacking in most stock enhancement efforts in coastal systems
  2. Establishing a governance framework for enhancements is largely ignored in stocking programs, thus, diminishing opportunities for integrating enhancement into fishery management
  3. Involvement of stakeholders in planning and execution of stocking programs is key from the start, but they are rarely made an integral part of program development
  4. adaptive management of stocking is not well integrated into enhancement plans, yet is critical to achieving goals, improving efficiencies, and understanding and controlling the effects of stocking on fisheries and on wild stocks.


Lorenzen, Leber & Blankenship (2010) expand on these points and emphasize the importance of their inclusion in the 'responsible approach' ( see updated list below). The updated approach is staged in order to ensure that key elements are implemented in the appropriate phases of development or reform processes. In particular, it is important to conduct broad-based and rigorous appraisal of enhancement contributions to fisheries management goals prior to more detailed research and technology development and operational implementation. This basic requirement applies to both development of new and/or reform of existing enhancements.  


The updated 'responsible approach' (Lorenzen, Leber & Blankenship, 2010):

    Stage I: Initial appraisal and goal setting

  1. understand the role of enhancement within the fishery system [NEW]
  2. Engage stakeholders and develop a rigorous and accountable decision making process [NEW]
  3. Quantitatively assess contributions of enhancement to fisheries management goals
  4. Prioritize and select target species and stocks for enhancement
  5. Assess economic and social benefits and costs of enhancement
  6. Stage II: Research and technology development including pilot studies

  7. Define enhancement system designs suitable for the fishery and management objectives [NEW]
  8. Develop appropriate aquaculture systems and rearing practices [NEW]
  9. Use genetic resource management to avoid deleterious genetic effects
  10. Use disease and health management
  11. Ensure that released hatchery fish can be identified
  12. Use an empirical process for defining optimal release strategies
  13. Stage III: Operational implementation and adaptive management

  14. Devise effective governance arrangements [NEW]
  15. Define a stock management plan with clear goals, measures of success and decision rules
  16. Assess and manage ecological impacts
  17. Use adaptive management


The knowledge gained through research on the kinds of issues presented here is now being used and expanded upon by scientists in this field worldwide to evaluate marine fisheries enhancements in fundamentally different habitats and conditions and at different spatial and temporal scales. Since 1990, science and knowledge in this field have expanded exponentially. Collectively, this work has begun to demonstrate how, and under what conditions, marine fisheries enhancements can complement current approaches to sustaining, restoring, conserving and enhancing marine and estuarine fisheries and fish (and invertebrate) populations.


For any given species, simultaneous consideration of all of the issues above requires a well-staffed, multi-disciplinary team, which can be assembled by pooling existing institutional resources through partnerships. For example, the scientists in our SCORE consortium span the range of disciplines and expertise needed to further advance the science of marine fisheries enhancement and its effectiveness as another tool in the fishery management toolbox. Don't hesitate to contact us is you are seeking advice or improvements for new and existing fisheries enhancement efforts.