Trifurcated Discovery: 1) size-at-age in exploited fish, 2) biomass spectrum in Northumberland Strait, and 3) finalising particle dispersion.

The proposal has 3 parts. First, is working with a student on a relatively new measure of ocean temperature and its relation to fish growth. It is the growing degree day metric (GGD) or thermal integral; a sum of heat transferred from the ocean to a fish. Fish are cold-blooded. More heat means better physiological functioning and larger size-at-age. Size-at-age is a growth integral. Thus, we expect a relation between the growth and thermal integrals. Recent work with a student shows this is precisely what we observe. Other researchers have now adopted the metric to examine various aspects of fish physiology. The metric is the one farmers use to determine crop ripening, but they use air temperature. We will expand our use of the metric across a suite of commercially valuable fish species because we have also shown that the GDD can be used to diagnose species and stocks that might be suffering from size-selective fishing. If a fishery preferentially targets the large fish, it is catching the fish that grow the fastest and mature the latest (maturation causes growth slow down). If this happens then the majority of the fish in the stock are smaller than they used to be at a given age, and they mature earlier. Also, when a stock suffers size-selective effects it becomes less sustainable. Smaller fish produce fewer eggs and the earlier maturing fish have less viable eggs and larvae. Increased evidence of the effects has raised concerns that they may be irreversible. We do know it becomes more difficult for a stock to replace itself. Thus fishing becomes less sustainable. If we can diagnose stocks showing size-selective effects, we can address pressing issues related to sustainable fisheries management, including recruitment (new fish) and changes in ecosystem structure, function and species diversity. We know the effects of unsustainable fishing, e.g., Canadian cod stocks, but now there is a selective fishing concern that the student and I, and a group of colleagues, wish to address before the consequences become apparent. Second, is working with a student and colleagues with similar interests to determine if the zooplankton (small crustaceans or sea fleas) biomass spectrum is a suitable measure of the functioning of the Northumberland Strait ecosystem. The biomass spectrum is a size-based measure of how much energy (e.g., calories) is in a body of water and how the energy varies in time and space when transferred through the food web from smaller to larger organisms such as fish, crabs and lobster that are critical ecological components of the Strait and represent a valuable fishery. The utility of the spectrum lies in its species independence that simplifies what would be more difficult from a species perspective. The value of studying the Strait is that it is somewhat like a pipe. It has inflow at one end of the Strait and outflow at the other, with known estuarine nutrient-input along the way. This simplifies what would be difficult and expensive to do the open ocean. If we show that the spectrum is suitable, then its utility becomes readily apparent to those involved in marine modeling and conservation interests such as integrated ecosystem management and the design of marine protected areas. Third, I wish to complete research with a student on our recently developed particle tracing technology to estimate early life-stage dispersal (transport and spreading) of aquatic organisms that is essential for explaining the connectivity of marine species. The technology, first of its kind, allows us to measure dispersal with real particles of the same size and buoyancy as biological particles (e.g., eggs and larvae). The research also contributes to improving numerical ocean models that struggle with small-scale diffusion processes.