I recently visited family in Illinois and, while flying there, talked with a fellow passenger about bitter crab disease and the prevalence of it in southeast Alaskan Tanner crabs (Chionoecetes bairdi). In one area, the parasitic dinoflagellate affected 95% of the crabs, and that was back in 1987! Lately some southeast Alaskan populations had 100% of their primiparous females infected (Sherry Tamone talked about that at the Alaska Marine Science Symposium in 2011). Bitter crab is a problem in Alaska, but it is also affecting fisheries off Virginia and along the eastern coastal US, as well as in crab hatcheries in China and lobster populations in Scotland! What is causing this, and how is it spreading? What can fishermen do to quell the infection rate? And how can processors assist the fishermen in this effort?
an infected Tanner crab (top) with milky hemolymph
and a healthy Tanner (bottom) with translucent hemolymph
Lots of questions, I know. Scientists have been feverishly researching Hematodinium sp, the dinoflagellate that is wreaking havoc on commercial crab species. A group of crab scientists at VIMS were able to trace the life history of Hematodinium sp. "[W]e can now really start picking the life cycle apart to learn what the organism does and how it functions," said Jeff Shields.
(Jeff Shields, VIMS)