An indeterminate model to estimate egg production of the highly iteroparous and fecund fish, dolphinfish (Coryphaena hippurus)

Abstract

Dolphinfish, Coryphaena hippurus Linnaeus, 1758, reproductive biology is well known, but this study, which examined gonad histology, substantially increases estimates of dolphinfish spawning fraction and annual egg production. Ovaries were collected from 621 females in three Florida regions: the Keys, Cape Canaveral, and the Panhandle. Maturation and spawning were evident in all three regions. Median size at maturity, 419 mm fork length (FL; 16.5 in, ?3 mo), was not regionally specific around Florida. Recruitment of primary oocytes to vitellogenesis occurred asynchronously throughout the spawning season, and mature oocytes developed group-synchronously as batches. Thus, an indeterminate method was required to estimate egg production. Once mature, females spawned 70-180 d yr-1. Some females spawned in all months of the year, but spawning fraction was highest in winter and spring. Batch fecundity (BF) ranged from 20,000 to 620,000 eggs and was significantly related to FL: BF = 0.000005 × FL3.62. An egg production model estimated a range from 15 to 174 million eggs yr-1, two orders of magnitude higher than the previous estimate (0.24-3.0 million eggs yr-1) in the Florida Straits. This new, higher estimate arises because our large sample size of gonad histology permitted estimation of spawning fraction throughout the year. Spawning early and often should make C. hippurus resilient to overfishing, but other data gaps�particularly regarding bycatch mortality�confound our ability to evaluate the effectiveness of size regulations in the fishery.