Sea surface temperature variation may affect food supply for Atlantic cod

Fluctuating ocean temperatures, coupled with changing patterns of water circulations could have a huge impact on food supply of young cods, researchers from the Northeast Fisheries Science Center claimed.

These changes in the ocean water could affect both - the quality and the quantity - of zooplankton, which may directly impact the recovery and number of Atlantic cod and other fishes in the Northeast US Continental Shelf.

"Temperature is a governing factor in the growth, reproduction and distribution of marine organisms. Shifting temperature distributions, whether triggered by natural or human factors, can cause the redistribution of plankton communities on regional and basin-wide scales," Kevin Friedland, a scientist at the NOAA's Northeast Fisheries Science Center and lead author of the study, explained.

Thermal change has been associated with a harmful effect on the ecosystem, and this study further confirms the fact. This may also cause an ecosystem imbalance, which is expected to show up on many levels of the food chain, the scientists speculate. "The geographic and depth distributions of fish and shellfish populations can also change based on their preferred thermal habitats. Future changes in thermal conditions are expected to lead to further shifts in the distributional ranges of species by, in many cases, the loss and gain of local populations," Friedland added.

Using the NEFSC's Ecosystem Monitoring Program, the researchers looked at the abundance of zooplankton species, which form an important food for many aquatic species. They further noticed that a thermal change was associated with a decrease in the number of zooplankton in that particular area. The researchers also analyzed data from the NEFSC's spring bottom trawl surveys.

Since zooplankton form an important prey for various marine animals, fishes in the early stage of life and marine mammals, a decrease in their number could directly affect the numbers of these marine species, the study emphasizes.

The research is published in the journal Progress in Oceanography, which is also available online. 

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