Genetic Impacts of Fish Introductions: Managing Stock and Biologic Diversity

1. Genetic and biologic stock management Hallerman Ch. 15 Genetic impacts of fish introductions BI 3063 J. Mork H08 Iteroparous organisms: Multiple reproduction cycles (successive years) Semelparous organisms: Reproduce only once in life INTRODUCTION Introductions and transfers of fish have a long history (carps and rainbow worldwide, Norwegian trout country-wide). Up to about 1960, transfers were regarded as desirable activities because of the possibility to enhance the output from fish farming as wells sportfishing. After a period with documentation of some very bad effects of introduction of new species into existing ecosystems, much more concern has characterised our perception of the practices. Actually, ICES have long had a special Working Group dealing specifically with problens connected with "exotic species" transfers. The WGITMO (Working Group on the Introductions and Transfers of Marine Organisms) has published a "Code of Practice" for such activities. A subset of the problems with species transfers, notably the genetic aspects, applies to introductions and transfers of within-species groupings. The problems ahve been particulatly accentuated in various species of Pacific salmonids.

2. Genetic and biologic stock management BI 3063 J. Mork H08 Hallerman Ch. 15 Genetic impacts of fish introductions Pink salmon (O. gorbuscha) Pacific salmonids Consensus phylogenetic tree of the Onchorhyncus genus. Based on morphological and molecular data. Branch lengths approximate relative divergences among taxa. (Hallerman Fig. 15-2)

3. Genetic and biologic stock management BI 3063 J. Mork H08 Hallerman Ch. 15 Genetic impacts of fish introductions Pacific salmonids Chinook O. tshawytscha Coho O. kisutch

4. Genetic and biologic stock management BI 3063 J. Mork H08 Hallerman Ch. 15 Genetic impacts of fish introductions Chinook Pink Chum Sockeye

5. Genetic and biologic stock management Hallerman Ch. 15 Genetic impacts of fish introductions BI 3063 J. Mork H08 DETECTION OF GENETIC CHANGES

6. Genetic and biologic stock management Hallerman Ch. 15 Genetic impacts of fish introductions BI 3063 J. Mork H08 • Traditional markers of genetic change • Morphological traits (hybrids) • Redd identification/counting • Timing/location of spawning • Migration changes • Karyotyping / chromosome studies • Molecular markers of genetic change • (since 1960- ies) • Redd identification/counting • Timing/location of spawning • Migration changes • Karyotyping / chromosome studies

7. Genetic and biologic stock management Hallerman Ch. 15 Genetic impacts of fish introductions BI 3063 J. Mork H08 POTENTIAL AND OBSERVED EFFECTS

8. Genetic and biologic stock management Hallerman Ch. 15 Genetic impacts of fish introductions BI 3063 J. Mork H08 Overview of potential effects of the release of exogeneous, hatchery-reared fish on native populations (from Utter 1998).

9. Genetic and biologic stock management BI 3063 J. Mork H08 Hallerman Ch. 15 Genetic impacts of fish introductions Box 15.1 Effect of supportive breeding on effectice size of total population Relation between the effective sizes of the contributing groups (wild or captivity bred) and the total population

10. Genetic and biologic stock management Hallerman Ch. 15 Genetic impacts of fish introductions BI 3063 J. Mork H08 A typical management scenario of supportive breeding: (x-es denotes relative contributions from the various groups) NW denotes wild fish NC denotes captive-bred fish

11. Genetic and biologic stock management Hallerman Ch. 15 Genetic impacts of fish introductions BI 3063 J. Mork H08

12. Genetic and biologic stock management Hallerman Ch. 15 Genetic impacts of fish introductions BI 3063 J. Mork H08 Indirect effects and side-effects of supportive breeding and introductions • Disease introduction (reducing sizes of natural populations -> drift effects) • Wastage of gametes (sterility or reduced fitness precludes reproductive success of hybrids • Fragmentation of habitats (displacements of native populations by naturalized nonnative groups Direct genetic effects through introgressive hybridization The effects depend on the resilience of natural populations to introgression, and this varies extensively with species and populations. All types of scenarios have been reported, from no effect at all and to a total wipe-out of native populations. In salmonids, virtually no case of introduction has been reported so far which is solely to the benefit of natural, native populations.

13. Genetic and biologic stock management BI 3063 J. Mork H08 Hallerman Ch. 15 Genetic impacts of fish introductions Observed effects of trans-locations and hybridizations on performance and fitness. Success stories are rare!

14. Genetic and biologic stock management Hallerman Ch. 15 Genetic impacts of fish introductions BI 3063 J. Mork H08 PERSPECTIVE ON INTRODUCTIONS The examples in this chapter have illustrated general areas of concern for the protection of native populations affected directly or indirectly by introductions. The basic principles for appropriately dealing with these concerns are thorougly documented in the scientific literature and management Codes of Practice. A very basic requirements is to identify existing genetic resources, i.e. thorough base-line studies must be performed in all cases. A firm knowledge of population structures underlies all other genetic concerns considering interactions of introduced and native populations, including - field studies (ecology) - laboratory studies (genetics) - desktop studies (evolutionary histories, invasion routes)

15. Genetic and biologic stock management Hallerman Ch. 15 Genetic impacts of fish introductions BI 3063 J. Mork H08 From a genetic conservation point of view, it has been stated that: "The best possible outcome of an introduction is a failure and thus a wasted effort". However, there may sometimes be good reasons for reinforcement of endangered wild populations, and hence there is a need for knowledge about all aspects of interactions and effects, in order to enable proper action when situations call for it. Such situations can be habitat destructions, reintroductions of populations that have been compromised by former, unfortunate practices. Prof. Nils Ryman at the University of Stockholm, a world expert on brown trout, described the current situation this way: " The globally increasing aquaculture industry will result in increasing incidental and intentional releases of huge numbers of fish, although those fish will represent a fairly low number of species and populations. Thus, the threat of hybridization from cutured fish to the genetic integrity of local populations must be considered a major concern".

16. Genetic and biologic stock management Hallerman Ch. 15 Genetic impacts of fish introductions BI 3063 J. Mork H08

17. Genetic and biologic stock management Hallerman Ch. 15 Genetic impacts of fish introductions BI 3063 J. Mork H08