Long-Term Changes in the Distribution of Larval and Mature Adult Fishes on the Northeast U.S. Shelf

Shifts in the distributions of marine fish populations over the past four decades have been attributed to climate and environmental changes, fishing pressure, and changes in population size.  Due to the complex life cycle of marine fish, changes in distribution among stages could disturb a successful transition across life-stage. We tested whether distributions of mature adult and larval fish have changed over the past 30 years on the northeast U.S. shelf.  In total, 59 taxa were examined from the Northeast Fisheries Science Center’s bottom trawl and ichthyoplankton programs. The relative proportion of mature adults and larvae within survey stratum were calculated and differences in proportions between two time periods 1977 to 1987 and 1999 to 2008 were calculated among the strata using a Kruskal-Wallis chi-square test. Linear regression was used to determine if distributions changed significantly in one of three ways: poleward, cross-shelf, or in depth.  Changes in distribution for taxa where both life-stages were examined were classified as in or out of sync.  Northward shifts in distributions were the most frequently observed for both life-stages.  Distribution shifts among life-stages were out of sync for about 55 % of the taxa examined, indicting potential disruptions in the transition between life-stages.