Monday, September 24, 2012
Even the fish are feeling the heat...
What about COD? (yeah, the fish)
Even fish are starting to feel the heat...
What about the state of cod populations off of the east coast of North America? Fish!? Yep, read on.
Cod fisheries hit peak landing totals in the late 1980s, but during the early 1990s catch tonnage along the entire US east coast and up into maritime Canada plummeted. Fisheries scientists found that cod populations were extremely depleted on both the Georges and Grand Banks, as well as on other traditional east coast fishing grounds. An unprecedented 10-year moratorium on commercial fishing was implemented in an effort to give the cod population a change to recover. Since cod are such an important food fish, fisheries managers work consistently to assess the health of cod stocks. This is done mainly via bottom trawl sampling. Little did fisheries managers know at the time that these cod trawl may provide insight into effects of climate change on marine species.
Cod are bottom fish, and though they do not need especially high levels of dissolved oxygen, they prefer cold water. So if water temperatures shift, that could affect cod distribution.
On 18 Sept 2012, the Northeast Fisheries Science Center (NEFSC) of the National Oceanographic and Atmospheric Administration (NOAA, Woods Hole, MA) released a report stating that 2012 produced the warmest seawater temperatures ever recorded off of New England. The NEFSC also released results of the latest bottom trawl survey designed to map the location and densities of Atlantic cod. The results were significant when compared to bottom trawl data from previous years. Look at the following trawl results from the following time periods.
By the way, areas closer to red indicate higher concentrations of cod. Areas closer to blue have very few to no cod present.
Here are the results from 1968-1972. Cod were present to relatively abundant in the coastal waters of NJ, NY, CN, RI, MA, NH, and ME, as well as in waters of the continental shelf west of MA, NH, and ME, and on up into Canada.
Here is the cod distribution 1973-1977 - similar to 1968-1972.
Here is the cod distribution 1978-1982 - similar to 1973-1977, except that there are fewer fish south of Long Island.
Here are the data from 1983-1987 - there are fewer cod inshore along the coast of Maine, but otherwise no major changes.
Here are the data from 1988-1992 - fish densities south of Long Island and in coastal Maine remain low.
The data for 1993-1997 show a significant decline in fish, and there are extremely few fish south of Cape Cop, and the number of fish offshore is and down. This suggests a lower population density of the cod, and that remaining cod appear to be moving north.
The data from 1998-2002 continue to show very few inshore cod south of Cape Cod.
These data from 2003-207 show an alarming decline in abundance, plus cod appear to be shifting northward more, with very few remaining in the Gulf of Maine.
Data from 2008-2012 confirm the data from 2003-200 with cod being found almost exclusively north of Cape Cod. This shift northward is correlated with increases in seawater temperature off of New England, and may represent a species-level response to water temperature change.
Northeast Fisheries Science Center - NOAA - Woods Hole, MA.
What about Arctic sea ice?