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Importance of Recruitment Cues for Maintenance of Upstream Populations of diadromous galaxiids in Protected Areas within New Zealand

Cindy Baker

National Institute of Water and Atmospheric Research (NIWA), HAMILTON, NEW ZEALAND

Theme: TH5

Protection of aquatic areas for management of specific faunal elements requires an understanding of recruitment dynamics for maintenance of population viability. In New Zealand, protected areas that encompass aquatic habitat and contain species of value are typically located at higher altitudes and not afforded the luxury of protective status when migrating to the sea. Of the 35 indigenous fish species in New Zealand, over half are diadromous and therefore require access to the sea to complete their life-cycle. Successful recruitment of juveniles is therefore pertinent to sustaining populations in protected headwaters. Recruitment strategies can be manifested in a variety of ways including the response to both physical and chemical environmental factors. Patterns of recruitment may be positively correlated to various habitat-specific cues, pheromonal cues produced by conspecifics, or other environmental variables. Knowledge of migration cues, which promote recruitment, has implications for the management of fish populations in protected areas. New Zealand contains five diadromous galaxiid species whose juvenile migrations comprise a nation-wide whitebait industry. This study demonstrated that juvenile galaxiids can discriminate and are attracted to odours produced by adult conspecifics, indeed the pheromonal attraction exhibited by one species was shown to override an avoidance of suspended sediments. To maintain protected diadromous fish populations, restoration and provision of suitable habitat may not be enough to positively influence juvenile recruitment; migration cues influencing recruitment to populations through unprotected migratory pathways are often crucial. This study has shown that pheromonal cues produced by adult conspecifics may enhance the maintenance of adult populations through their encouragement of juvenile recruitment to upstream protected areas.