FORAGING BEHAVIOR AND MEMORY WINDOW IN STICKLEBACKS

Individuals were collected from a residential marine population of Spi nachia spinachia, an anadromous population of Gasterosteus aculeatus f orma trachura and a residential freshwater population of G. aculeatus forma leiura. After maintenance for 2 months on a diet of mysid, indiv iduals were subjected to ten, consecutive daily trials on a diet of am phipods or oligochaetes. During this period, individuals learned to ha ndle the prey more effectively, as measured by attack efficiency, hand ling efficiency and handling time. Learning was similar among populati ons but differed between diets, being more pronounced for amphipods, w hich are more difficult to catch and handle than oligochaetes. Once tr ained to these diets, fish were tested for foraging efficiency after s uccessively longer periods of stimulus deprivation, when they were fed a maintenance diet of mysid. All three measures of foraging efficienc y with the amphipod diet, but only that based on handling time with th e oligochaete diet, declined to naive levels in the residential marine and anadromous populations. No decrease in foraging efficiency with e ither diet occurred in the residential freshwater population. Memory w indow was 8 d, 10 d and > 25 d in the residential marine, anadromous a nd residential freshwater populations respectively. The large differen ce between the freshwater and two marine populations is interpreted as an adaptive response to the stability of arrays of prey, characterist ic of their respective habitats.