Isotope geochemistry reveals ontogeny of dispersal and exchange between main-river and tributary habitats in smallmouth bass Micropterus dolomieu.
Radiogenic strontium isotope ratios (87Sr:86Sr) in otoliths were compared with isotope ratios predicted from models and observed in water sampling to reconstruct the movement histories of smallmouth bass Micropterus dolomieu between main-river and adjacent tributary habitats. A mechanistic model incorporating isotope geochemistry, weathering processes and basin accumulation reasonably predicted observed river87Sr:86Sr across the study area and provided the foundations for experimental design and inferring fish provenance. Exchange between rivers occurred frequently, with nearly half (48%) of the 209 individuals displaying changes in otolith87Sr:86Sr reflecting movement between isotopically distinct rivers. The majority of between-river movements occurred in the first year and often within the first few months of life. Although more individuals were observed moving from the main river into tributaries, this pattern did not necessarily reflect asymmetry in exchange. Several individuals made multiple movements between rivers over their lifetimes; no patterns were found, however, that suggest seasonal or migratory movement. The main-river sport fishery is strongly supported by recruitment from tributary spawning, as 26% of stock size individuals in the main river were spawned in tributaries. The prevailing pattern of early juvenile dispersal documented in this study has not been observed previously for this species and suggests that the process of establishing seasonal home-range areas occurs up to 2 years earlier than originally hypothesized. Extensive exchange between rivers would have substantial implications for management of M. dolomieu populations in river-tributary networks.
Biology Department, Washington and Lee University, 204 West Washington St, Lexington, VA, 24450, U.S.A.
R
R
Humston
Biology Department, Washington and Lee University, 204 West Washington St, Lexington, VA, 24450, U.S.A.
S S
SS
Doss
Biology Department, Washington and Lee University, 204 West Washington St, Lexington, VA, 24450, U.S.A.
C
C
Wass
Environmental Studies Program, Washington and Lee University, 204 West Washington St, Lexington, VA, 24450, U.S.A.
C
C
Hollenbeck
Biology Department, Woods Hole Oceanographic Institution, 266 Woods Hole Road, Woods Hole, MA, 02543, U.S.A.
S R
SR
Thorrold
Virginia Department of Game and Inland Fisheries, 1132 Thomas Jefferson Rd, Forest, VA, 24551, U.S.A.
S
S
Smith
Geology Department, University of North Carolina, 104 South Road, Mitchell Hall, Campus Box #3315, Chapel Hill, NC, 27599, U.S.A.
C P
CP
Bataille
D063147:Animal Distribution; D000818:Animals; D001492:Bass / Q000502:physiology*; D003247:Conservation of Natural Resources; D017753:Ecosystem; D008962:Models, Theoretical; D010037:Otolithic Membrane / Q000737:chemistry*; D045483:Rivers / Q000737:chemistry; D013326:Strontium Radioisotopes
D013326:Strontium Radioisotopes
fish movement; otolith chemistry; river networks; strontium isotope ratio