Fish Spawning Earlier Off California Coasts

school of fish photo

Photo by evilthomthai via Flickr Creative Commons

Fish living in waters off California's coasts are changing the timing of their reproductive cycles, new studies show. Eighteen of the area's most common species are spawning 15 to 62 days earlier than what was common in the 1950s, while eight other species are spawning between 15 and 38 days later. While experts aren't sure why the trends are occurring, they're eyeballing changes in water temperature as a culprit. FishRap News reports that California Sea Grant researchers have found that fish larvae counts in water samples collected during the California Cooperative Oceanic Fisheries Investigations (CalCOFI) cruises, which began in the early 1950s, have shifted. Because sea surface temperatures in California waters are reaching their seasonal peak roughly 25 days earlier than in the 1950s, it's likely the waters' warmth that is causing the fish to alter their spawning times.

"We don't know why there is this trend toward earlier spawning," California Sea Grant trainee Rebecca Asch, a doctoral student at Scripps Institution of Oceanography at UC San Diego, told FishRap News. "But, it's likely related to temperature. Many marine organisms use temperature as a cue for when to initiate spawning, so the idea that changes in seasonal temperatures would affect spawning time shouldn't come as too much of a surprise."

Oceanic water temperatures world wide are warming, and fish aren't the only species changing their historical habits. Corals too are suffering from rising temperatures, and even such durable species as starfish and plankton are feeling the heat.

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