Blue crab larval dispersal highlights population connectivity and implications for fishery management

Abstract

In the Western Atlantic and Gulf of Mexico (GOM), the blue crab Callinectes sapidus fishery is managed at a regional scale, and its assessment does not consider the population structure of the species. To understand connectivity of the blue crab population, we simulated larval dispersal using a biophysical model driven by high-resolution ocean currents and including early life-history traits of the species. Simulations were conducted during 2015 and 2016, and larvae were released from locations along Florida's GOM and Atlantic coasts. A high degree of local larval retention was observed in Florida's GOM waters, mainly during summer when weak southeastern winds tend to yield a shoreward net flow. Results demonstrated clear evidence of connectivity between the Gulf coast of Florida population and those of Mississippi, Alabama, and Louisiana, suggesting that the blue crab populations in the GOM are intermixed and the hypothesized boundary (in Florida) of 2 stocks needs further consideration. Outputs of the model also indicated connectivity between the blue crab populations of Florida's Gulf coast and the South Atlantic Bight (SAB). Larval trajectories showed inter-annual variability driven by the interaction of winds, Loop Current (LC) intrusions in the northern GOM, LC eddies and their cyclonic counterparts, and the Mississippi River plume. The latter provides a conduit for larval transport from the GOM to the SAB. These findings provide evidence of the physical oceanographic processes that sustain the homogenous genetic population structure for blue crabs between SAB and GOM populations, highlighting the need for collaborative management in US waters.

Blue Crab Spawning and Recruitment in Two Gulf Coast and Two Atlantic Estuaries in Florida

“…Trends in age-0 catch show that in most Florida estuaries, recruitment occurs year round to some degree, even though no spawning aggregations are present nearby. These results were confirmed by Criales et al (2019), who demonstrated that there was a high degree of larval retention during summer in Florida estuaries, accounting for age-0 abundance peaks in fall and winter. Criales et al (2019) also found evidence of connectivity between waters of other Gulf states, Florida waters, and the South Atlantic Bight.…”

Distribution, relative abundance, and reproductive output of spawning female blue crab (Callinectes sapidus) in offshore waters of the Gulf of Mexico

“…The large numbers of blue crab caught offshore of Louisiana relative to catch in other regions likely reflect the low salinities present in estuaries of Louisiana. Egg hatching and larval survivorship is negatively affected by salinities <20.1 (Costlow and Bookhout, 1959); during the spawning migration, therefore, females move to spawning grounds suitable for offspring survival. It is possible that the low salinities in estuaries of Louisiana result in greater numbers 9 NMFS (National Marine Fisheries Service).…”

“…After mating, female blue crab forage for several weeks (Turner et al, 2003) before beginning a seaward spawning migration (Aguilar et al, 2005). This migration ensures that females reach spawning grounds of sufficiently high salinity (>20.1; Costlow and Bookhout, 1959) for larval survival. Spawning female blue crab are often found in large numbers at or near the mouths of estuaries (e.g., Rittschof et al, 2010;Anderson et al, 2017); these areas are typically assumed to be the primary spawning grounds.…”

“…The blue crab is a highly fecund species, with females producing multiple clutches of several million larvae at a time (Hines et al, 2003). Each brood of larvae is released into the water column as zoeae that disperse through currents for 30-50 d (Costlow and Bookhout, 1959) before their return and recruitment to coastal habitat as megalopae soon after (Rabalais et al, 1995;Ogburn et al, 2009).…”

Coral Reefs in the Gulf of Mexico Large Marine Ecosystem: Conservation Status, Challenges, and Opportunities

“…Recent modeling studies on virtual larvae have allowed detection of trajectories illustrating habitat connectivity. For example, Criales et al (2019) studied blue crab (Callinectes sapidus) showing variable larval dispersal pathways between 2015 and 2016, which were driven by the interaction of winds, the Mississippi River plume, Loop Current intrusions in the northern GoM, Loop Current eddies, and their cyclonic counterparts. Their findings supported the homogeneous genetic population structure of C. sapidus among Mid-Atlantic and GoM populations, as the Mississippi River plume provided a conduit to transport virtual larvae to the South Atlantic Bight.…”