Whether you are a Jackson Browne fan or not - there is one critter in the ocean that just may be 'running on empty'. And it is about time this swimming critter gets a proper introduction from the Ecosystem Modeling Lab.
If you ever had salmon on your dinner plate, it most likely was not wild Atlantic salmon. We have all heard the about the glories of eating omega-3 fatty acids and that salmon are loaded with that stuff. You ecologists in the audience also recognize that salmon serve as an important nutrient link between marine, freshwater, and terrestrial ecosystems.
Despite decades of conservation efforts, Atlantic salmon populations are still declining. If we want to restore Atlantic salmon populations we need to better understand the marine-phase of their life cycle.
A lot of money and research has focused on the freshwater life-phase of Atlantic salmon in the form of habitat restoration and hatchery breeding and restocking programs. Despite these efforts we have not seen the response in population increase we would expect to see.
The salmon get counted as they leave the rivers and then get counted again as they return to the rivers. From these counts, we know that mortality in the ocean is high.
Salmon are easier to study in freshwater environments because they are shallow water and you can easily see the fish. Salmon are much more difficult to study in the ocean because they are more difficult to track. Tracking involves tagging devices that inherently have a low recovery rate or are typically cost prohibitive. This is one reason why we know relatively little about what factors influence salmon mortality as they migrate through the ocean.
The reality is that the persistence of the species of Atlantic salmon is heavily dependent on human intervention and management. Wild Atlantic salmon are on life support. Right now most of this management focuses on only one of two critical habitats this species utilizes during its life cycle. Enhanced research efforts on the ocean life-phase of Atlantic salmon will provide information that can be used to better manage this species.
So what is the Ecosystem Modeling Lab doing about it?
We are trying to uncover some of the mystery shrouding the high marine-phase mortality. We are attacking this mystery from a few different angles. Kathy Mills has been busying herself pulling together relevant data and information looking for trends in the timing of life-cycle events over the past several decades. Meanwhile, I busy myself building a computer model that will allow us to track swimming and growing particles (a.k.a. young salmon) across the Gulf of Maine (GoM). In the near future, questions that come out of Kathy's research can hopefully be examined using my model, which will be much more cost and time efficient than trying to track live fish in the vast ocean.
Assuming that a blog on ecosystem modeling attracts other ecosystem modelers, I will just briefly touch on a few characteristics of the model but will attempt to keep the lingo G rated for a general audience. We have considerable reason to believe that marine-phase mortality is highest just as they are entering the ocean. Therefore, we are focused on the outmigration of post-smolts (see life-cycle diagram attached) as they move through the GoM. The physical data informing the model comes from buoys in the GoM. Growth and the energetic costs of swimming across the GoM is calculated using the Wisconsin model (so named because it was developed by researchers at University of Wisconsin, which happens to also be my alma mater). We know the post-smolts make it to coast of Halifax a few months after leaving the rivers in Maine so we gave our particles a swimming speed and direction pointing towards Halifax. The particles are then released from a river site at a specified time corresponding to their outmigration, and left to swim towards Halifax while experiencing their oceanographic environment - which means that currents and temperature are able to impact their swimming pathways and growth. For more information regarding the model, please email me at email@example.com.So, Are Atlantic salmon running on empty? Do individuals have enough food to provide energy for their great migration? Are populations large enough to withstand predator attacks? Is the changing environment suitable and stable enough to allow persistence of this species? Stay tuned as we are still in quest for the answers to these questions.