Guest Column: Where do whales feed?

First published in the MLA Newsletter, January, 2011.

Researchers Andy Pershing and Jeff Runge from the Gulf of Maine Research Institute and the University of Maine, along with Erin Summers from the Department of Marine Resources, are conducting a research project in response to the suggestion by lobstermen that right whales do not come inshore to eat. The background to this is the whale entanglement issue. The fishing industry argued that it didn’t make sense to make big investments in new ropes since they don’t see right whales where they fish. The research will be used to identify feeding “hotspots,” so to speak, so that regulations can be targeted to specific locations instead of imposing blanket measures across the entire industry.

The program started in 2008 and is funded by the lobster industry through trap tag fees. The third and final year has been funded through money appropriated by Congress through the National Marine Fisheries Service. It was originally earmarked for float rope buybacks but some of it has been reallocated to relevant whale research such as this.

The hypothesis that fishermen offered was that right whales don’t come inshore to eat because there isn’t enough food for them. The team came up with a research plan to test this. The main foodstuff of right whales is called Calanus finmarchicus. These are zooplankton known as copepods. About the size of a grain of rice, these copepods are quite large compared to other plankton and also happen to be the main food stuff of herring. They are important to many other species as well.

Calanus finmarchicus is a deep ocean and subarctic species and is most abundant in the deeper waters in the Gulf of Maine. While the scientists knew they were a deep ocean species they didn’t know how their abundance changes closer to shore. Is the boundary abrupt? Does it change from season to season or year to year? What might cause the boundary to break down and encourage right whales to hang around an area, maybe closer to land than usual?

The researchers did survey work over the past three summers. They chose July as the survey month because it’s the time of year when the lipid-rich life stages of Calanus finmarchicus are most evident – though not necessarily the time when there are the most whale sightings. The research vessels they used were the R/V Stellwagon and Gulf Challenger (University of New Hampshire). They surveyed along transect lines at a series of stations working from inshore to offshore. They measured salinity and temperature and recorded how these change with depth. They also carried out plankton net tows, looking at the density of different zooplankton species.

It will come as no surprise that counting plankton isn’t easy and so the researchers used a high tech instrument called a laser optical plankton counter. You can’t conclusively identify the species with this, but you can tell the size of the animals and whether the species are spread out or in a dense layer.

The research team then did more targeted studies at specific stations, for longer periods of time, to see if there were differences from day to night. They also repeated net samples to look at growth and mortality of the copepods. They were testing the hypothesis that the transition between Calanus finmarchicus presence inshore and offshore is maintained either through increased mortality inshore or through ocean currents.

So what do the results look like so far? Under average conditions, researchers observed the transition to higher abundances of Calanus finmarchicus which is above the feeding threshold for a right whale in water deeper than 50 fathoms, meaning that the evidence supports the original hypothesis suggested by fishermen. What is not so clear and still being researched are the ‘non-average’ conditions. As any fisherman knows, conditions in the ocean change quickly and often. There are likely times when there are bigger flows of Calanus finmarchicus rich offshore water coming inshore, and work on this will continue for a while yet.

It is really satisfying to see researchers take the views of fishermen based on their daily working knowledge of the sea. That said, it can be frustrating for industry members waiting to hear the results of what is unavoidably a lengthy research process. Oceanographic processes are complex and one research question often leads to another as the issue gets refined along the way.

A further interesting dimension to the research is the interdependence of the lobster and herring industries. In helping initiate this research related to whales, the lobster industry also contributed to the research being carried out on the prime food source of Gulf of Maine herring, and it could be useful for interested lobstermen to engage in discussions around current and future herring research when they get the opportunity.

But for me there is another important side to this story and that is the importance of this particular little zooplankton to understanding climate change in the Gulf of Maine. Because of its abundance and its capacity to accumulate stores of lipids, Calanus finmarchicus is very important in the food chain. We know they are at the southern limit of their geographic range and are very sensitive to increases in water temperature. We also have evidence that they do not survive any significant increase in ocean acidification. So, while there is no current evidence of this, when flowed into a forecasting model, the data provides vital information about the potential impact of such changing climate conditions on the Gulf of Maine’s ecosystem.

Research scientists Andy, Jeff and Erin plan to present their work and findings at the Fishermen’s Forum next March. This will be a great opportunity to learn more about Calanus finnmarchicus and its role in the ecosystem, as well as hear the results of the research related to Calanus finmarchicus abundances found in near shore waters. Fishing industry members will have an opportunity to ask questions and get fully up to speed on whether whales come near shore to feed or not.