Effects of the toxic dinoflagellate, Alexandrium fundyense on three species of larval fish: a food‐chain approach

Sublethal behavioural effects of exposure to paralytic shellfish toxins (PST; saxitoxin and its derivatives) from the toxic dinoflagellate Alexandrium fundyense were investigated in newly settled winter flounder Pseudopleuronectes americanus , larval sheepshead minnow Cyprinodon variegatus and larval mummichog Fundulus heteroclitus through an A. fundyense –copepod–fish food chain. Consumption of as few as six to 12 toxin‐containing copepods was lethal to the fishes. After consuming fewer toxin‐containing copepods, all three fish species exhibited sublethal effects from vector‐mediated exposure. Prey‐capture ability of mummichogs was reduced in larvae that had consumed toxic copepods, Coullana canadensis . After consuming toxic C. canadensis or mixed copepods, mummichog larvae had reduced swimming performance. Swimming activity was also significantly reduced in winter flounder after consuming toxic copepods, including time spent in motion and distance travelled. Prey capture and predator avoidance were reduced in first‐feeding sheepshead minnow larvae that had consumed toxic dinoflagellate cells. Adverse effects on prey capture or predator avoidance may reduce larval survival and facilitate the transmission of PST through the food web. This study provides baseline information on sublethal effects of PST exposure on fishes using a novel food‐chain approach with zooplankton as vectors.