Poissons sans frontiers: Comparing contiguous surveys for major ecological and commercial species in the Northwest Atlantic, with a focus on trends, synchronies and coherences

No abstracts are to be cited without prior reference to the author.

Fish know no national borders, yet for a plethora of reasons, we delineate fish into distinct population or stock units that often reflect human institutional borders more so than biological factors. Across a wide variety of taxa, population dynamics can be synchronous over a range of spatial scales. Common patterns are generally attributed to a meta-population structure supported through dispersal, or a common response to large scale environmental forcing. In the NW Atlantic, common species occur in the broader Gulf of Maine Area (GOMA), yet the area is managed in the south by the US and in the north by Canada. Many species occurring in the GOMA are subject to common forcing resulting in coherent patterns of recruitment and growth among distinct populations. To evaluate these issues, we compared six survey biomass time series of 19 representative species from US and Canadian waters. We further explored the biomass trends of aggregate groups such as the top 13 groundfish or total fish biomass. Many of these individual species and aggregates species groupings showed synchronous trends. For instance, Canadian and US populations of haddock, thorny skate and white hake have comparable trends within species. Conversely, some species show differing survey time series trends and asynchronous event timing, suggesting forcing processes may influence these species differently. Collectively our results demonstrate the value of comparing time-series for common species from contiguous ecosystems, with the potential to elucidate the relative importance of major factors affecting such species