Spatial variation and evidence of multiple transport pathways for Dungeness crab Cancer magister late-stage larvae in southeastern Alaska

The fate of early life stages can affect the spatial and temporal population dynamics of managed marine populations. Early Dungeness crab Cancer magister larval stages off the west coast of the contiguous United States migrate out of estuaries, develop on or beyond the continental shelf, and return to nearshore areas prior to settlement. Whether a similar ontogenetic movement pattern exists for C. magister larvae in southeastern Alaska is unknown. Extrapolation is difficult due to differences between the Alaska Coastal Current and California Current oceanographic domains and to the complex coastline, high-amplitude tides, and the large amount of freshwater influx in Alaska. We investigated the temporal and spatial variations in abundance and size of C. magister megalopae in the northern portion of southeastern Alaska. We found a high degree of spatial variation in the abundance of C. magister megalopae on both local (2 to 6 km) and regional (300+ km) scales. Although temporal differences were found among sites on a regional scale, there was no order in the arrival time of the pulse from the outer coast to the inside waters. The abundance of megalopae was higher in Icy Strait, which contained 3 out of 4 of the highest abundance sites, than at sites in Chatham Strait or Lynn Canal. Larvae varied in size and weight among these 3 regions. Due to spatial variation in abundance and larval size, as well as the lack of ordered pulse arrival times and the potentially isolating currents proposed by computer simulation, we propose multiple transport pathways for C. magister populations in northern southeastern Alaska.