Nearly all of the marine fish and shellfish living along coastlines release microscopic larvae into the open ocean. The larvae then disperse for weeks to months before settling back into coral reefs and kelp forests. The larvae are too small and they travel too far to be tracked directly. Yet, knowing where these larvae settle is important for conservation and management. By quantifying the origins of a reef’s population, one can determine the extent to which that reef is dependent on other fish and shellfish populations for the replenishment of the next generation. Understanding these patterns of “connectivity” and “dependency” among reefs is critical for determining how to best protect, fish, and manage our coastlines. To complicate matters, connectivity patterns change annually. An example of such changes along the Pacific Coast of North America has to do with El Niño’s, which occur every few years, and generate warm, northward-flowing ocean currents that transport marine larva up the coast. Thus, it is hypothesized that El Niño’s can make northern reefs dependent on southern populations for new supplies of fish and shellfish. There is evidence showing that El Niños will increase in frequency and intensity with the changing climate, and because strategic management of fisheries in relation to effects of El Niño on connectivity could produce large gains in catches and profit, such present and future implications of El Niño events highlight the importance of studying them when the occur.
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