EGG MASSES OF LOLIGO OPALESCENS (CEPHALOPODA: MYOPSIDA) IN MONTEREY BAY, CALIFORNIA FOLLOWING THE EL NINO EVENT OF 1997-1998

摘要

The commercial fishery for Loligo opalescens (Berry 1911) off the coast of California collapsed in 1998 following the 1997 El Nino event. Nonetheless, small schools of adult squid in non-commercial quantities routinely were attracted to night-lights below boats anchored near Monterey Harbor. Accordingly, Monterey Bay was searched for egg beds with sonar, an ROV, and with SCUBA during September and October 1998 to see if adults were spawning. Scattered egg masses were found with brown capsules in the center surrounded by more recently deposited white capsules with embryonic developmental differences of at least eight days. Brown capsules may provide visual stimulus for repeated site-specific spawning, 'hotspot' lek behavior. The egg masses were composed of multiple cohorts with capsule dimensions highly correlated to developmental stage. Means of 164 (SD = 20, n = 193) eggs/capsule and 259 (SD = 212, n = 13) capsules/mass were found, with 152 egg masses in the most concentrated 1000 m~2 of the egg bed. The expected number of eggs was 6.46 x 10~6 for this 1000 m~2. The sea star Asterina miniata (Brandt, 1835) was observed feeding on the egg masses 26 times in Monterey Bay. In the laboratory the A. miniata and the gastropods Kelletia kelletii (Forbes, 1850) and Cypraea spadicea (Swainson, 1836) ate Loligo eggs.