Use of prophylactic treatments for larval rearing of giant crabs Pseudocarcinus gigas (Lamarck)

Chemicals were screened for prophylactic treatment of epibiotic fouling and fungal mycosis in larvae of the temperate crab Pseudocarcinus gigas. The following treatments were applied as indefinite baths: oxytetracycline, trifluralin, carbendazim, copper oxychloride, malachite green, and formalin. Most effective treatments for improving survival were oxytetracycline (25 mg l-1, despite increased deformity), trifluralin (0.01 mg l-1), carbendazim (0.001 mg l-1), and copper oxychloride (0.05 mg l-1). Three of these treatments affected size and shape of the megalopa carapace with relatively smaller megalopas developing in carbendazim and trifluralin, and relatively broader megalopas in copper oxychloride. Toxic effects, measured by increased mortality, deformity, death during ecdysis, or delayed ecdysis, were recorded with oxytetracycline (≤ 25 mg l-1), trifluralin (≤ 0.03 mg l-1), malachite green (≤ 0.1 mg l-1), and formalin (for all concentrations tested: ≤ 2.5 mg l-1).