Infection by marine Vlbrlo bacteria is still considered to be
the major opportunistic cause of mass mortalities of pearl
oysters (Pinctada maxima} on farm lease sites in the north
west of Western Australia. Vibriosis of P. maxima was found
to occur following some form of stressful husbandry practice
as similar mortality outbreaks were never apparent in natural
populations of pearl oysters throughout this investigation.
Potentially harmful Vlbrlo species were found to be associated
with pearl oysters in the Broome region throughout the year;
therefore vibriosis could occur at any time to oysters
subjected to excessive stress.

1 A method was developed to rapidly assess the effectiveness of trap designs and identify
the causes of differences in effectiveness.
2 Fish entry and escape probabilities are correlated across trap designs. The probabilities
are very high for '0' and 'S' trap designs and are much lower for the 'Z' design. Traps
with high entry and escape probabilities are best for a fishing strategy based on short
soak times, while traps with low probabilities are best for strategies using long set
times. 'Z' traps provide a greater catch per set than 'S' traps for soaks longer than about
4 h, while 'S' traps provide better catches for soaks shorter than about 4 h.