Diadromous Fish of the

Northwest Atlantic


The Fish

Historically, diadromous fish contributed to the sustenance and economic growth of the Atlantic states. However, since the industrial revolution the tolls of environmental stress, overfishing, and habitat loss were to become apparent in the longest settled parts of the country (Field 1914, Oviatt et al. 2003). Although there is now a popular drive to remove dams (Born et al. 1998, Crane 2005), with the benefit of reintroducing and rehabilitating diadromous fish runs (Lindloff 2003, Hill 2007) the unavoidable question is whether the domino effect of collapsing runs and species can be reversed. In many places dams were the coup-de-grace, eradicating diadromous fish runs altogether (NRC 2004). Beyond dams, multiple stressors have continued to complicate diadromous fish recovery in most locations. Debris choked rivers in New England and Maritime Canada before the 1960s (Perley 1852, Rounsefell and Stringer 1945) and chemicals and toxins remain a persistent problem (McMaster et al. 2006). Fish communities within rivers and estuaries have changed considerably since the full compliment of diadromous fishes were abundant. The most recent challenge faced by diadromous fish is global climate change and the predictions of physical habitat change and range shifts for diadromous species (NRC 2004, Solomon et al. 2007).

Weight of evidence suggests that single-species management may not change the fate of Atlantic salmon and other declining diadromous species (Pauly et al. 2002). Almost 4 million smolts and parr were stocked in Maine rivers in 2004 with a two-year return of just over 1,000 adults, a 0.03% return rate (Keliher 2004; Maine Atlantic Salmon Commission 2006 unpublished data). There may be a complex interplay within the diadromous species assemblage that has yet to be explored. In Pacific salmon interplay between species is an accepted paradigm (Cederholm et al. 1999, Naiman et al. 2002, Schindler et al. 2003), but in North Atlantic rivers the potential interactions between a diverse community of diadromous fishes is only just being addressed. For example, spring spawning species in Atlantic rivers deposit marine-derived nutrients in freshwater habitats (Durbin et al. 1979, Browder and Garman 1994, Cunjak et al. 2007) and have overlapping spawning habitats (e.g., lamprey and Atlantic salmon; Nislow and Kynard 2007). Like a jigsaw puzzle, loss of one piece may be preventing other interlocking ecological relationships from occurring in these rivers, suppressing production in the full suite of diadromous fish.




Fish Species



Below is a list of the diadromous fish species of the Northwest Atlantic Ocean which includes the Canadian Maritme Provinces and the US Atlantlic States. The following weblinks provide information on these species.




Diadromous Fish Species: