Reproductive Structures and Early Life History of the Gulf Toadfish, Opsanus beta, in the Tecolutla Estuary, Veracruz, Mexico

Although the Gulf toadfish, Opsanus beta, is an abundant member of the nearshore Gulf of Mexico ichthyofaunal assemblage, little information exists regarding the ecology of the species, especially for southern Gulf of Mexico populations. We added to the existing knowledge of this species by describing the reproductive structures and examining the early life history of this species in the Tecolutla estuary, Mexico. Macro- and microscopic examination of 7 males showed spermatogenesis to be similar to other teleost species except for the occurrence of biflagellate spermatozoa. Histological examination of the male accessory gland showed 3 tissue layers, but their functions are still undetermined. We found asynchronous development of oocytes in the ovaries of 16 females, which may indicate multiple spawning over the long spawning season noted in this study. Batch fecundity estimates among females ranged from 79 to 518 mature ova with a mean ovum diameter of 3.5 mm. The above-mentioned factors along with large size at hatching, attached larval forms, and paternal care may account, in part, for the abundance of this species in highly dynamic systems

Reducing the Effects of Dredged Material Levees On Coastal Marsh Function: Sediment Deposition and Nekton Utilization

Dredged material levees in coastal Louisiana are normally associated with pipeline canals or, more frequently, canals dredged through the wetlands to allow access to drilling locations for mineral extraction. The hydrologic impact on marshes behind the levee is of concern to coastal resource managers because of the potential impact on sediment transport and deposition, and the effect on estuarine organism access to valuable nursery habitat. This study examined the effects of gaps in dredged material levees, compared to continuous levees and natural channel banks, on these two aspects of marsh function. Field studies for sediment deposition were conducted biweekly for a year, and nekton samples were collected in spring and fall. Variation in nekton density among study arears and landscape types was great in part because of the inherent sampling gear issues and in part because of differences in characteristics among areas. Nekton densities were generally greater in natural compared to leveed and gapped landscapes. Differences in landscape type did not explain patterns in sediment deposition. The gaps examined appear to be too restrictive of marsh flooding to provide efficient movements of floodwaters onto the marsh during moderate flooding events. The trapping effect of the levees increases sediment deposition during extreme events. Gapping material levees may be an effective method of partially restoring upper marsh connection to nekton, but this method may work best in lower elevation marshes where nekton use is greater

Olfactory deterrents to black drum predation on oyster leases

Black drum (Pogonias cromis) predation is a serious threat to oyster production on Louisiana leases, and leaseholders hypothesize that black drum carcasses suspended above leases deter predation. We conducted experiments under laboratory and field conditions to test whether the scent of dead con-specifics deterred black drum predation. Preliminary experiments indicated that fish \u3e70 cm total length were effective predators, and oysters \u3c70 g wet total weight were preferred, and we used these sizes in subsequent experiments. Salinity did not affect feeding rates. Experiments in 30,000 L raceways indicated that scent did not significantly lower feeding rates. Parametric analyses of factorial experiments on oyster leases at two sites in Barataria Bay, Louisiana, during the fall and spring (periods of the year when fish feeding is most intense), indicated that scent reduced feeding rates by 10% to 20%, but only at one site in one season. Nonparametric analyses corroborated seasonal differences indicated by parametric analyses, but not the scent effect. We therefore conclude that scent from dead con-specifics is not an effective control strategy under most conditions. Dredge hauls during experiments suggested mortalities to all predators ranging from 63.1% to 92.5% within the first 4 weeks after seeding. The relative mortalities to black drum, southern oyster drills (Stramonita haemastoma) or possibly Perkinsus murinus infections varied among sites, as did temporal patterns of mortality within and among seasons