Responsible approach to restocking and stock enhancement

Transcription

1 Responsible approach to restocking and stock enhancement Josianne Støttrup, Dept. For Marine Ecology and Aquaculture

2 The Responsible Approach Blankenship and Leber, key components essential to control and optimise stock enhancement. Examples from Danish marine stocking experiments and the

3 The 10 components can essentially be grouped according to 3 phases. What to consider before attempting stocking (define whether it is restocking or stock enhancement) How to ensure an optimal stocking program What to assess, evaluate to monitor/optimise the stocking

4 The Responsible approach 1.Prioritise and select target species for enhancement Community survey Local experts In Denmark, fishermen (commercial and recreational) make suggestions for specific species in specific areas. OR, aquaculture enterprise make suggestions for releases E e t ou the look at the Source: Blankenship & Leber, 1995

5 The Responsible approach 2. Develop a species management plan that identifies harvest opportunity, stock rebuilding goals and genetic objectives Goals and objectives for restocking or stock enhancement Clearly identified genetic structure Source: Blankenship & Leber, 1995 and geographic distribution of the

6 AIM: 10% enhancement of an average 2-year-old yearclass in ICES area 25 = 17 million recruits Bornholm Introduction

7 The Responsible Approach (cont.) 6. Consider ecological, biological and life history patterns when forming enhancement objective and tactics Source: Blankenship & Leber, 1995

8 Oxygen content (ml/l) S a lin ity (p su ) Depth (m ) Baltic Sea Ecology Salinity O xygen

9 1. Recruitment bottleneck not directly related to fisheries Bornholm basin 3. Low predation pressure > FF Inflow of saline water from Kattegat Cod egg habitat after water inflow Cod egg habitat Before water inflow Oxygen free layer Baltic Sea Ecology

10 April-June Technical University of Denmark Jan Feb Mar Apr Maj Jun Jul Aug Sept Okt Nov Dec 2. A food resource not exploited by the natural population of today Baltic Sea Ecology

11 The Responsible Approach (cont.) 9. Identify economic and policy guidelines Source: Blankenship & Leber, 1995

12 Rearing requirements Scenario I Scenario II Scenario III Age at release 3-month First-feeding Eggs Magnitude per year 26 million 474 million 13 billion Requirements Female for broodstock ,558 Capital costs* 4.41 mill 341, mill Running costs 1.93 mill 204, ,000 Area requirement Broodstock 594m², Egg incubators 108m², Live feed production 396m², Hatchery 2484m², Ongrowing 5355m². Broodstock 594m², Egg incubators 30m², Broodstock 2078m², Egg incubators 356m², Economic analysis Running costs: 2 million DKr Expected return: million DKr

13 The Responsible approach (cont.) What to consider before attempting stocking (define whether it is restocking or stock enhancement) How to ensure an optimal stocking program What to assess, evaluate to optimise the stocking program

14 The Responsible approach 3. Define quantitative measure of success Set quantitative goals Use simple indicators The Danish Baltic Sea Case Study: Goal of 10% increase in average year class recruits. Increase the Spawning Stock Biomass by min. 10% while < tons. Source: Blankenship & Leber, 1995

15 Number of 2-year-old recruits Good environmental conditions Poor environmental conditions SSB ca t in 2005

16 The Responsible approach 4. Use genetic resource management to avoid deleterious genetic effects Identify genetic risks and consequences of enhancement and how to mitigate Implement genetic controls in the hatchery and a monitoring and evaluation program for wild stocks Source: Blankenship & Leber, 1995 Implement a sufficiently large

17 The Responsible approach 5. Use disease and health management Establish maximum acceptable levels of infections and parasites in the hatchery established on the basis of wild stock health screening results. BVP monitoring program established for Danish Baltic Sea broodstock Source: Blankenship & Leber, 1995

18 The Responsible approach (cont.) What to consider before attempting stocking (define whether it is restocking or stock enhancement) How to ensure an optimal stocking program What to assess, evaluate to optimise the stocking program

19 The Responsible Approach (cont.) 7. Identify released hatchery fish and assess stocking impacts

20 The Responsible Approach (cont.) 8. Use an empirical process for defining optimum release strategies Trial at 1% increase target. Source: Blankenship & Leber, 1995

21 The Responsible Approach (cont.) 10. Use adaptive management. Continuous process to improve stocking results by reviewing all components, some degree of monitoring and adapting. New ideas for refining stock enhancement/ restocking constantly considered and i di h Source: Blankenship & Leber, 1995