J. Korman et al., DEVELOPMENT AND EVALUATION OF A BIOLOGICAL MODEL TO ASSESS REGIONAL-SCALE EFFECTS OF ACIDIFICATION ON ATLANTIC SALMON (SALMO-SALAR), Canadian journal of fisheries and aquatic sciences, 51(3), 1994, pp. 662-680
We developed an age-structured simulation model incorporating pH-depen
dent mortality to assess impacts of acidification on Atlantic salmon (
Salmo salar) populations at the reach and river system level. Applied
to the LaHave River, Nova Scotia, acidic reaches (mean annual pH 4.6-5
.1) were predicted to have 0-15% of the annual smolt production and 0-
31% of the maiden spawner production compared with circumneutral reach
es (pH greater-than-or-equal-to 5.6) and increased juvenile growth due
to lower parr densities. The benefit of increased growth (earlier age
of smoltification and increased early marine survival) was not suffic
ient to outweigh impacts of higher freshwater juvenile mortality. Simu
lated removal of acidic conditions resulted in a 41% increase in recru
its, but only after several decades following complete chemical recove
ry. Circumneutral reaches were predicted to be 4-12 times more efficie
nt at producing smolts and 3-7 times more efficient at producing adult
s from hatchery fingerlings compared with acidic reaches. To maintain
current target egg deposition rates of 240 eggs/100 m2, circumneutral
reaches could withstand grilse exploitation rates of up to 65%, while
acidic reaches, even without harvesting mortality, could not maintain
this level. Fisheries management strategies need to account for variab
ility in freshwater production both within and between river systems.