Adaptive Management Projects

Project Summary: Salmonid Enhancement Project

A huge amount of money and effort has been invested in the Salmonid Enhancement Program (SEP) since its inception in the 1970's. However, the value and effectiveness of a number of strategies in SEP have been questioned. Critics say that, in some cases, the strategies were implemented without adequate controls and replication, so that it is now difficult to determine whether changes in salmon populations are a result of the strategy or other factors.

Management Issue:

Are hatcheries a worthwhile investment?

Hatcheries were built to increase populations (and catches) of adult salmon, by increasing the number of fry released.

The value and effectiveness of these hatcheries are subject to debate. Results are ambiguous because the hatcheries were typically evaluated by comparing the size of runs before the hatchery was built to the size of runs after (i.e., with no spatial or temporal replication or controls). It is therefore difficult to assess whether changes (or lack of changes) are a result of the hatchery or other factors, such as ocean conditions, fishing pressure, or continued habitat destruction.

For example, coho catches have not increased despite the extensive investment in hatcheries and increased release of fry, and wild stocks have declined. But, because the "experiment" of introducing hatcheries was poorly designed, it is impossible to tell why. There is continued uncertainty about the best strategy for increasing the size of runs.

Management Issue:

Are spawning channels for sockeye salmon a worthwhile investment?

A number of artificial spawning channels were constructed on streams feeding Babine Lake to increase the catch of sockeye salmon by increasing the release of fry.

Again, results are ambiguous and open to debate because they are based on before and after comparisons; they were not compared to changes in returns to streams without channels.

Although adult returns to the Babine increased after spawning channels were built, this could have been the result of one or more of the following:

• increased fry production from the spawing channels (in which case the spawning channels may be a worthwhile investment - depending on the size of the increase);
• habitat recovery (after an earlier landslide substantially reduced stocks);
• reduced fishing pressure (in response to the stock reductions caused by the slide);
• other unknown factors (other large sockeye runs - without channels - showed increases during the same period).

Furthermore, increases in Babine stocks may have decreased stocks from other streams (because of density dependent interactions or increased fishing pressure).

On other systems with spawning channels, there has been little increase in total return of adults. However, it is impossible to determine why without being able to compare results to controls, and without adequate monitoring.

The Department of Fisheries and Oceans invested in 2 more spawning channels despite the ambiguity of these results and debate over the value of spawning channels.

Costs of not applying adaptive management:

• continued operation of potentially ineffective or detrimental facilities;
• additional investment in new facilities that may not yield any benefit;
• potential continued negative impacts on wild stocks;
• loss of opportunity to investigate or invest in other strategies for enhancing salmon populations.

References:

Hilborn, R. 1992. Institutional learning and spawning channels for sockeye salmon (Onchorynchus nerka). Canadian Journal of Fisheries and Aquatic Science 49: 1126-1136.

Walters, C.J. 1993. Dynamic models and large scale field experiments in environmental impact assessment and management. Australian Journal of Ecology 18:53-61.

McAllister, M. K. and R.M. Peterman. 1992b. Experimental design in the management of fisheries: a review. North American Journal of Fisheries Management 12:1-8.