Survival of captive milkfish Chanos chanos Forsskal broodstock subjected to handling and transport

The survival of milkfish broodstock (body weight range 1-11 kg) was determi ned until 30 days after handling and transport in open tanks or in sealed o xygenated bags containing chilled sea water (20-25 degrees C). Maintenance of cool sea water was achieved by the gradual addition of ice chunks or fro zen gel packs. A survival rate of 50% after transporting fish at a loading density of 45 kg m(-3) for 4 h in open tanks was not significantly differen t from those that were handled but not transported (86%). Similarly, surviv al rates (67-83%) among broodstock confined for 8 h in chilled sea water at 40 and 60 kg m(-3) were not significantly different from each other or fro m a group not subjected to confinement. Nevertheless, low dissolved oxygen (DO) and accumulation of total ammonia-nitrogen beginning Ih after transpor t and confinement may be responsible for low survival rates of milkfish in open tanks. In contrast, all milkfish survived 10 h of overland transport i n sealed bags with chilled and diluted (28 g L-1) sea water. Likewise, all milkfish survived after being bagged and immediately transferred to a commu nal rearing tank, or bagged and placed in a styrofoam box for 10 h. Except for total ammonia-nitrogen levels, which increased slightly (0.7-0.8 mg L-1 ) above background, seawater temperature (20-24 degrees C), salinity (28 g L-1) and DO (6 to > 20 mg mL(-1)) titres in transport bags were maintained during the 10-h test. The effectiveness Df handling and transporting milkfi sh broodstock in sealed bags containing chilled sea water was verified in a ctual field trials. Spawning of sexually mature milkfish subjected to these stressors was not impaired. These results demonstrate that mortalities of large milkfish broodstock can be minimized when fish are handled and transp orted in sealed oxygenated bags containing chilled sea water.