New York Weather News - Jeff's Weather Blog

It seems that the ocean temperatures have been unseasonably warm for late July. This past weekend, the water was literally a bath tub. According to the chart from Rutgers on the left, the great south bay has already warmed to around 80 and south facing shores are in the mid 70's. Climate change and ocean temperature change affect coastal fishing. According to the US Global Change Research Program, water temperature, fishing methods, and combined effects, including changes in predator-prey relationships influence the abundance of fish. It can be difficult to separate which circumstances create which results. However, some observations indicate trends in the impacts of environmental conditions on coastal fisheries.

During the 1970s and 1980s, populations in many of the Northeast's commercially important fisheries, such as cod, haddock, and yellowtail flounder plummeted. Although over-fishing is often cited as the major cause of these population declines, an additional explanation is that ocean warming played a role in altering the distribution and reproductive success of coastal species. Interactions between temperature and salinity, which can be altered with changes in temperature and precipitation, determine the range that a species can tolerate and successfully inhabit.

Changes in species composition already have occurred all along the North Atlantic coast. One example will be used to illustrate the complexity of this issue. Over a 30-year observation period from 1959 to 1989, the community composition shifted in Narragansett Bay, Rhode Island, from a resident cold-water, winter flounder dominant community to a migratory, warmer-water marine community. Warmer water temperatures appear to have set off a chain of circumstances that began with the loss of the winter flounder population and resulted in increased populations of invertebrates and migrant fishes. During this period, the winter flounder population crashed on two occasions. Both times occurred during a multi-year warming trend during the winter-spring spawning period. A recovery of the winter flounder populations coincided with two successive cold winters. Moreover, large invertebrates -- such as crabs, squid, lobster (only in the Bay), and mantis shrimp -- moved into the region earlier in the season and in greater numbers. By the third decade of observation, the butterfish, originally a summer migrant species, had increased so much that it ranked fourth in abundance in the Narragansett Bay area.

Scientists have suggested that warm temperatures in late winter-early spring allow shrimp, one of the invertebrates increasing in number, to feed earlier in the year than usual. They invade the flounder's cold-water estuarine refuge and feed on its larvae at rates sufficient to remove a significant number. This same effect has been observed in the North Sea between plaice and a common shrimp.