Effects of Four Insecticides on the Ability of Atlantic Salmon Parr (<i>Salmo salar</i>) to Learn and Retain a Simple Conditioned Response

Abstract

The learning ability of untreated, acetone-treated, and insecticide-treated Atlantic salmon parr was determined in a shuttlebox conditioning apparatus. Learning improvement on second conditioning was also tested.The results were that: (1), acetone did not affect learning; (2), with treatment for 24 hr at the 96-hr LC50 Sumithion ® completely inhibited learning, Abate ® retarded learning, DDT mildly enhanced learning, and methoxychlor was without a detectable effect; (3), when Abate and methoxychlor-treated salmon in item (2) above were retrained 1 or 7 days later their learning ability improved; but DDT-treated fish showed no improvement; (4), four days of recovery from a 24-hr exposure to the 96-hr LC50 of Abate or Sumithion still resulted in slow learning ability, although after 7 days of recovery learning rate was the same as that of controls; (5), insecticide treatment at the 96-hr LC50 level for 24 hr interposed between first and second conditioning had little or no effect on learning ability; (6), insecticide concentrations at one-tenth the 96-hr LC50 or lower had no effect on learning ability.