Reproductive Characteristics of Weakfish in Delaware Bay: Implications for Management

Abstract

We quantified size and age at maturity, batch fecundity, spawning frequency, and annual fecundity for weakfish Cynoscion regalis in Delaware Bay in 1999 and 2000. Information about these critical characteristics are needed for stock assessment models, which have never been assessed in Delaware Bay nor anywhere in the range of the weakfish since 1991–1992, when abundance was very low. Stock size increased from 1991–1992 to 1999–2000, but size at maturity was 168 ± 4.1 mm (mean ± SE) and did not appear to increase with stock size. Ninety-seven percent of age-1 fish were mature, but they arrived later to the estuary, had lower batch fecundity, and spawned less frequently than did older fish. The annual fecundity of fish age 2–6 was at least 30 times as great as that of age-1 fish. Batch fecundity was similar between Chesapeake Bay and Delaware Bay in the same year once corrected for fish size. The relationships of batch fecundity to both female weight and length were statistically equal between the two time periods in which batch fecundity has been quantified (1991–1992 and 1999–2000). However, we did detect differences in batch fecundity at age and the length–weight relationship over time. The difference in the length–weight relationship is due to the absence of large (>400 mm) and old (>4 years) females and indicates that the population has not recovered to its former stock structure. The absence of large females could lead to lower egg production than expected and may help explain the slow recovery of this species. We suggest decreasing the proportion of mature fish at age 1 to account for the low egg production of this age-class and to continue efforts to enhance the size and age structure of the population.