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Daily Ovarian and Spawning Cycles in Weakfish
Author(s) -
Taylor Malcolm H.,
Villoso Enrico P.
Publication year - 1994
Publication title -
transactions of the american fisheries society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.696
H-Index - 86
eISSN - 1548-8659
pISSN - 0002-8487
DOI - 10.1577/1548-8659(1994)123<0009:doasci>2.3.co;2
Subject(s) - fecundity , gonadosomatic index , biology , bay , population , zoology , fish <actinopterygii> , fishery , oceanography , demography , sociology , geology
A spawning population of weakfish Cynoscion regalis in Delaware Bay was sampled on May 27, 29, and 30, 1988, to relate the daily timing of spawning to the ovarian cycle. Spawning was concentrated over several hours in early evening, ending soon after sundown. Female gonadosomatic index (GSI), proportion of females with hydrated oocytes, and percentage of hydrated oocytes in ovaries were all at or near daily maxima at 1700 hours and declined precipitously by 2000 hours. Although all females examined contained hydrated oocytes on each of the three nights of the study, GSI, numbers of hydrated oocytes, and fecundity decreased by the last night. These results suggest that individual female weakfish spawned for several days in succession and became, at least temporarily, depleted by the end of that period. Sampling on June 10, 13, and 21 documented additional spawning by fish in the size range collected in May, but GSI and fecundity were lower in the June collections. Estimation of seasonal fecundity for weakfish is complicated by the apparent irregularity of intervals between spawns and the progressive decline in batch fecundity.