Science Talks

Science Talk I - Dave Mountain of the Northeast Fisheries Science Center gave an excellent presentation on the potential consequences of climate change on fish resources in the NW Atlantic/Georges Bank region. His study area included both the Gulf of Maine and the Middle Atlantic Bight. Dave noted that there were approximately 180 species of fish in the region and that 60% of these were cold temperate, the rest warm temperate species. The region is therefore a faunal transition area. The Gulf of Maine mixes water from two main sources. The first source is cool, fresh water from the Scotain Shelf. The second input is warm salty slope water. Temperature changes are expected to be in the 2 to 4° range. However, the temperature in any one place can vary 12-20° annually and 2-4° changes seem minor. There should also be an increase in the Labrador Current. However, both of these changes should increase stratification and this is perhaps where the important differences are. Additionally, stratification involves some nonlinearities and strong feedback mechanisms. For example there can be 20% more buoyancy produced from a unit of heat at 6.5° than at 4.5°.

If one examines fall temperature anomalies over the entire shelf, the 1960's were cool and then temperatures have moved back and forth. Some fish exhibit distributional shifts within this time frame. Mackerel distributions were southerly in 1968 when compared to 1974 when it was warmer. A relationship seems to exist between mackerel latitude and temperature. Haddock, with a different life history and spawning strategy, did not exhibit a large change in distribution. They did, however, seem to use deeper water as temperatures increased on the Bank. This implies that the impact may be taxa or species specific. While mackerel may change latitude, haddock may change where they are located on the Bank. Both of these factors can impact population dynamics. Retention on Georges Bank is dependent on location. If haddock spawn in deeper water, retention on the Bank may suffer. Also, haddock may move into a region where there are stronger predator/prey interactions with larval gadids. Additionally, temperature will influence physiological rates.

There have also been significant changes in the volume ratio of the sources for the Gulf of Maine from between the mid 1970s and the early 1990s. Between 1976 and 1979 65%(35%) of the water entiring the GOM came from the slope(Scotian Shelf). Between 1993 and 1996 this ratio had virtually reversed and with only 32%(68%)from the slope(Scotian Shelf). These differences are significant and will have very important implications for the physics and biology of the entire study region.

It is likely the case that these changes have their origins in processes such as NAO. If we can understand the local manifestation of these processes and place the life history within that framework, we may be able to address climate change concerns in a meaningful way.

Science Talk II - John Quinlan, new to the program office as of June, gave a science talk which focused on how GLOBEC technology could be used in the design and assessment of Marine Protected Areas in the coastal ocean. This essentially represents an effort to move toward an operational setting for the GLOBEC models. The talk covered individual-based and hydrodynamic modeling which contributed to the South Atlantic Bight Recruitment Experiment and Georges Bank GLOBEC. In an extension of Craig Lewis' work, these techniques are being applied to sea scallop population dynamics along the east coast of the United States. Initial results are suggestive of connectance between different scallop subpopulations from Georges Bank to the Virginia Beach area. This talk led to a discussion of defining habitats of special concern (ie, those supplying recruits to particular areas) and how to use the modeling to define areas that are unsuitable for marine reserves due to a lack of connectance. Questions of how to properly handle zooplankton and other biological fields were raised, especially with respect to small scale patchiness and microstructure.