IMPLICATIONS OF HARMFUL MICROALGAE AND HETEROTROPHIC DINOFLAGELLATES IN MANAGEMENT OF SUSTAINABLE MARINE FISHERIES

Worldwide increases in the frequency and spatial extent of blooms of h armful marine microalgae and heterotrophic dinoflagellates suggest tha t these species are becoming an increasingly important influence on ye ar class strength of marine fishes through both direct and indirect me chanisms. Impacts on fish populations from harmful marine microalgae a nd heterotrophic dinoflagellates have been considered primarily from t he limited view of acute or lethal influences. Accumulating evidence i ndicates that insidious sublethal and chronic impacts to both fish and human health from these organisms, such as long-term behavior alterat ion, increased susceptibility to cancers and other diseases, depressed feeding, and impaired reproduction, may be substantial and pervasive. For some harmful species, significant indirect impacts that promote c ritical habitat loss or disrupt the microbial food web balance also ha ve been documented. Because successful models to predict the behavior and growth of most of these species have not yet been developed, and b ecause toxins for many are poorly characterized, a clear anthropocentr ic focus has guided management strategies for confronting their outbre aks. The extent to which management takes the fundamental step of ackn owledging scientifically demonstrated linkages among harmful microalga e, shellfish contamination, fish kills, and human health impacts has a lso been seriously constrained by political dictates stemming from eco nomic considerations. Without federal involvement, and without catastr ophe of human death or widescale serious human illness, little progres s historically has been realized in the development of effective manag ement strategies to mitigate lethal impacts to fish or other organisms . Many long-known taxa such as certain ''red tide'' dinoflagellates ap parently can increase independently of human influences other than phy sical transport. However, some newly discovered toxic or otherwise har mful taxa have been correlated with cultural eutrophication in poorly flushed fish nursery grounds such as estuaries and coastal waters. Out breaks of certain warm-optimal species have coincided with El Ni (n) o ver tilde o events, suggesting that warming trends in global climate c hange may stimulate their growth and extend or shift their range. The available information points to a critical need for a more proactive, concerted effort to determine the full range of chronic/sublethal effe cts, as well as acute impacts, on marine fish populations by harmful m arine microalgae and heterotrophic dinoflagellates, so that their incr easingly important influence can be factored into reliable plans for s ustainable fisheries management.