 Crangon nigromaculata
 Distribution of Crangon nigricauda in San
Francisco Bay
Crangon nigricauda (the blacktail bay shrimp) ranges from Prince William Sound,
Alaska to Baja California and is found in estuaries and the nearshore ocean area.
Over the entire study period, C. nigricauda has been the second most abundant
species of caridean shrimp collected in the Bay. It is less tolerant of low
salinities than C. franciscorum and is not common upstream of San Pablo Bay even
during years with low freshwater outflow.
Based on our collections of ovigerous C. nigricauda, peak spawning occurs in the
winter. Most juveniles settle in late spring and are common in shallow, intermediate
salinity (>15.5‰) water. As for C. franciscorum, juveniles were collected in warmer,
lower salinity waters than adults.
Female C. nigricauda mature at approximately 33 mm total length (TL) and males at
approximately 28 mm TL in San Francisco Bay. Both sexes mature at one year; males
probably spawn once and die while some females may live to two years. The maximum
sizes of C. nigricauda collected by this study are 64 mm TL for females and 60 mm TL
for males.
Annual abundance indices of Crangon nigricauda were low in the early 1980's, but
increased through the 1987-1992 drought. C. nigricauda abundance remained high in
1993 in spite of increased freshwater outflow and decreased salinities. From 1988
through 1993, C. nigricauda was the most abundant species of shrimp collected in the
Bay. Undoubtedly, this species benefited from the higher salinities associated with
the drought, especially during the winter and spring.
Annual abundance indices for C. nigricauda are generated
from the San Francisco Bay Monitoring Program
otter trawl data.
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