HARVESTING MULTIPLE STOCKS OF DUCKS

This study was conducted to help assess whether recent harvest rates o f ducks banded before the hunting season in the United States varied a mong stocks (i.e., species, age-sex cohort, location of banding) and w hether regulatory actions have been successful at shifting harvest pre ssure among stocks in the desired manner. Direct recovery rates during 1976-91 were used to index harvest rates and were influenced to some degree by location of banding, age class, sex, species, and hunting re gulations. However, differences in recovery probability among species were consistent (P = 0.787) over 3 periods with different hunting regu lations (1976-84, 1985-87, 1988-91), despite regulatory changes design ed to affect species differentially. Band-recovery models that exclude d the interaction between hunting regulations and sex of ducks were in adequate (P less than or equal to 0.013), suggesting sex-specific chan ges in recovery probabilites with changes in regulations. There was li ttle evidence (P less than or equal to 0.151) that regulatory changes affected recovery rates of ducks from 3 banding reference areas differ entially. Harvesting duck stocks in an optimal manner requires an abil ity to harvest selectively, a good understanding of each stock's dynam ics, and knowledge of any interdependence in stock sizes.