Spatial Variation and Evidence for Multiple Transport Pathways for Dungeness Crab (Cancer Magister) Late-stage Larvae in Southeastern Alaska PDF Download
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Author: Quinn T. Smith Publisher: ISBN: Category : Dungeness crab Languages : en Pages : 104
Book Description
"Time series of larval abundance collected with light traps reveal large pulses of Dungeness crab (Cancer magister) late-stage larvae (megalopae) in Glacier Bay, with high variability among years. Because it is unclear whether processes affecting larval supply in Glacier Bay are broadly applicable to the larger region of southeastern Alaska, and whether larval abundances inside a marine reserve are different from areas with commercial fishing, I investigated megalopae abundance in the surrounding region. Megalopae abundances in Berner's Bay, 60 km further inland was 56 times smaller than the Glacier Bay site. In 2006, I increased the geographic extent of sampling along a 350 km gradient from the outer coast to the inside waters. I found that Glacier Bay had, on average, five times more megalopae than other sites. A 2-D tidal circulation model suggests a circulation barrier east of Glacier Bay. Morphometric differences in megalopae suggest a difference in larval size on either side of the barrier, indicating that larvae may have multiple transport pathways into inside waters. In summary, C. magister megalopae abundance in southeastern Alaska is highly spatially variable; circulation patterns in southeastern Alaska are complex, and multiple transport pathways for early stages of C. magister are likely"--Leaf iii.
Author: Quinn T. Smith Publisher: ISBN: Category : Dungeness crab Languages : en Pages : 104
Book Description
"Time series of larval abundance collected with light traps reveal large pulses of Dungeness crab (Cancer magister) late-stage larvae (megalopae) in Glacier Bay, with high variability among years. Because it is unclear whether processes affecting larval supply in Glacier Bay are broadly applicable to the larger region of southeastern Alaska, and whether larval abundances inside a marine reserve are different from areas with commercial fishing, I investigated megalopae abundance in the surrounding region. Megalopae abundances in Berner's Bay, 60 km further inland was 56 times smaller than the Glacier Bay site. In 2006, I increased the geographic extent of sampling along a 350 km gradient from the outer coast to the inside waters. I found that Glacier Bay had, on average, five times more megalopae than other sites. A 2-D tidal circulation model suggests a circulation barrier east of Glacier Bay. Morphometric differences in megalopae suggest a difference in larval size on either side of the barrier, indicating that larvae may have multiple transport pathways into inside waters. In summary, C. magister megalopae abundance in southeastern Alaska is highly spatially variable; circulation patterns in southeastern Alaska are complex, and multiple transport pathways for early stages of C. magister are likely"--Leaf iii.
Author: Wongyu Park Publisher: ISBN: 9780549069089 Category : Dungeness crab Languages : en Pages : 165
Book Description
Mixing, loss, and distribution of larval Dungeness crabs were investigated inside and outside of Glacier Bay, southeastern Alaska, biweekly from late May to mid-September and monthly in Icy Strait from late May to late August in 2004. Larvae were collected from two different portions of the water column: above and below the thermocline and at four stations in Icy Strait. Larval loss was markedly high for ZI, ZIV, and ZV, and relatively low for ZII and ZIII. ZI occurred from late May to late July. Larval stages progressed seasonally from ZI to ZV and density decreased from ZI through ZV. The larval densities at the inner and outer bay stations and at the shallow and deep depths were similar.
Author: Heidi L. Herter Publisher: ISBN: Category : Dungeness crab Languages : en Pages : 110
Book Description
"Areas of high Cancer magister larval recruitment and transport mechanisms were identified in the lower portion of Glacier Bay, Alaska. Megalopae were collected at three sites in 2004 and 2005 using light traps positioned within 1 m of the surface and bottom at 10 m depth. Surface traps captured 96.5 - 99.4 % of megalopae collected. Megalopae abundances were highly pulsed and decreased with increasing distance from the mouth of Glacier Bay. Spatial variation was similar between years with significant differences among all sites in 2005. Half of the total annual megalopae supply occurred over just two nights in September or October, the dates of which varied by location. Megalopae abundance in Bartlett Cove was negatively cross-correlated with tidal amplitude at -3 to + 1 d lags and positively cross-correlated with maximum wind speed at a 0 d lag. Megalopae abundance in the South Beardslee Islands was positively correlated with tidal amplitude and negatively correlated with maximum wind speed at +2 to +3 d lags. Abundance in the North Beardslee Islands was low and not correlated with tides or winds. Spatial variation in megalopae abundance and correlations between abundances and transport processes suggests that Dungeness crab megalopae are transported into Glacier Bay"--Leaf iii.
Author: Tyler M. Jackson Publisher: ISBN: Category : Crab populations Languages : en Pages : 89
Book Description
Understanding connectivity among exploited populations is critical to their sustainable management and long-term viability. In the marine environment, estimates of connectivity often rely on the use of genetic markers, as dispersal primarily occurs during a planktonic larval phase which is difficult to track using direct methods. In this thesis, we investigated the population genetic structure of the most valuable commercially harvested species on the west coast of the United States, the Dungeness crab (Cancer magister). We utilized both population- and individual-based genetic analyses to establish baseline knowledge of genetic connectivity of Dungeness crab throughout ~1,200 km of the California Current System (CCS) in 2012, and tested for inter-annual variability in our estimates by sampling again in 2014. In 2012, we observed a pattern of isolation by distance despite there being little genetic population structure throughout our study range. In addition, several sites had significant evidence of kin aggregation, which was correlated with genetic differentiation as measured by pairwise FST. In 2014, pairwise FST estimates were noticeably lower, there was no spatial autocorrelation, and fewer sights had significant evidence of kin aggregation. We attributed these findings to increased migrant exchange during potential larval dispersal years, which was mediated by variation in physical oceanographic conditions (i.e. Pacific Decadal Oscillation phase, timing of the spring transition, amount of upwelling during the spring and summer). Dispersal trajectory, and thus gene flow, is likely influenced by variation in physical oceanographic conditions, thereby affecting genetic population structure. Estimates of effective population size (N[subscript E]) indicated that N[subscript E] was large in both 2012 and 2014, but we were unable to discern any change between years. Together, these findings suggest that Dungeness crab in the CCS may constitute a single evolutionary population, though geographically limited dispersal results in isolation by distance. We also evaluated genetic connectivity among Dungeness crab inhabiting a partially enclosed water body, Puget Sound, in comparison to those residing in the coastal ocean. With the exception of Hood Canal, we observed genetic homogeneity within both Puget Sound and coastal Washington. Genetic differentiation between Puget Sound and coastal Washington was variable among sites, therefore genetic connectivity is stronger within either area than between them. Overall, our results suggest that Dungeness crab exemplify characteristics of a ‘high gene flow’ species, despite evidence supporting geographically limited gene flow. Our findings did not indicate that altering the management strategy to reflect discrete genetic subunits or conversation needs (i.e. low genetic diversity) is necessary at this time. In addition, our findings highlight the need for future research to investigate demographic processes that influence gene flow (i.e. dispersal trajectory).
Author: Megan M. Murphy Publisher: ISBN: Category : Crabs Languages : en Pages : 200
Book Description
"This study's primary goal was to understand the oceanographic effects on larval crab transport and distribution between an estuarine inner and more oceanic outer bay in the subarctic estuary of Kachemak Bay, Alaska. Plankton tows and hydrographic measurements (temperature and salinity) were taken along the boundary between the two bay parts from March - October on spring and neap tides. Summer water flow and in Kachemak Bay is predominantly freshwater-driven and density patterns vary inter-annually with the amount of freshwater supplied to the inner bay. Larvae of seven crab species occurred in a seasonal sequence and the crab larval assemblage was closely correlated to temperature in the upper 20 m. The influence of tidal forcing on larval transport was not clear even though most species exhibited peak abundances at spring tides. Larval distribution patterns across the inner/outer boundary indicated that Oregonia gracilis larvae may be transported into inner Kachemak Bay; however, late larval stages of the two commercially relevant species, Chionoecetes bairdi and Cancer magister, were never observed and may be exported from the inner estuary. These observations provide an important baseline for further studies to understand Kachemak Bay's role as a source or sink for larval crab"--Leaf iii.
Author: Quinn T. Smith
Author: Quinn T. Smith
Author: Wongyu Park
Author: Heidi L. Herter
Author: Roderick C. Hobbs
Author: Tyler M. Jackson
Author: Megan M. Murphy
Author: Leif Kevin Rasmuson
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Author: Lois Julia Hollett
Author: James R. Mackovjak