Reproductive Success in Atlantic Croaker, Micropogonias undulates (Linnaeus), Collected from Galveston Bay, Texas: Study of a Mixed Contaminant Estuary
The reproductive success of Atlantic croaker, Micropogonias undulatus, collected from two sites in the northwest section of the Houston Ship Channel and one site in Bayport Ship Channel in Galveston Bay, Texas was assessed in October 1993. Contaminant levels at the sites differ due to the amount and type of anthropogenic discharge along the Channel itself and in adjacent bays, with the San Jacinto and Tabbs Bay areas being heavily contaminated and Bayport Channel less contaminated. Individual spawns from sixty pairs of adult fish were inspected for egg quality and success of fertilization, hatch, and 39 and 63 h survival. Tabbs Bay had the highest percentage of unsuccessful spawns, 70.8%, followed by Bayport (32.0%), and San Jacinto (18.2%). Hatch was the critical time point in development due to the low success for all three sites (68.0& Bayport, 45.8% Tabbs Bay, 81.2% San Jacinto). San Jacinto had the most abnormal larvae at hatch, 26.3%, while Tabbs Bay had the highest percentage of dead abnormal larvae at 63 h, 51.8%. Less than 10% of the larvae at Bayport showed morphological abnormalities at any time point. Observations of larval response to a water jet or sound stimulation showed increasing trends with age of the larvae at Bayport Channel. At Tabbs Bay, there was evidence of impaired behavioral response as the larvae aged to both water jet and sound stimulation. Ovarian levels of ascorbic acid were significantly lower in the Tabbs Bay fish relative to those from the other sites. Conditions of the Houston Ship Channel in the Tabbs Bay region during October 1993 were detrimental to the reproductive success of M. undulatus, exerting the most influence at hatching of the embryo. Due to the physical and ecological similarities between sites, it is thought that the differing contaminant loads contributed to the differences seen between sites in larval survival, abnormalities, behavioral response, and adult ovarian ascorbic acid levels.