The newly hatched larvae are called zoea, and being planktonic, can be pulled all over the inner continental shelf. The zoeae molt into megalopae, which are able to swim to a limited degree and thus vertically migrate through the water column to find appropriate currents (created by the and Ekman spiral) that will bring them back to suitable habitat in the near-shore estuaries where they were first conceived. Since the entire larval (zoea) and post-larval (megalops) development stages take place over 1 to 2 months, the larvae are highly subjected to wind and currents and, depending on conditions, may travel hundreds of miles from the position of where they were spawned before they must harness the energy of the currents and find their way back to suitable habitat. This fact, combined with the fact that, as plankton, they are also very vulnerable to predation leads to the conclusion that the larval development stages are the weak link in the blue crab life cycle. Once the megalopae find an estuary, they molt into juveniles. Being much more abled swimmers, juveniles will seek out lower salinity waters near river deltas that contain submerged aquatic vegetation (SAV) that provide protection and a concentration of food. The juveniles will continue to grow in the same location they settled in and will reach sexual maturity the following spring or summer. Most blue crabs are estimated to have a 3 year lifespan and can reach a maximum size of 9 inches from tip to tip of the carapace.
No comments:
Post a Comment