Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001. 2nd edition revised

The Florida Fish and Wildlife Conservation Commission’s Florida Marine Research Institute (FWC-FMRI) has examined total mercury levels in muscle tissue from a variety of economically and ecologically important species as part of an ongoing study to better understand mercury contamination in marine fishes.The FWC-FMRI Mercury Program is one of the most comprehensive programs in the United States for monitoring mercury levels in marine and estuarine fishes. Because mercury, a toxic metallic element, has been shown to bioaccumulate in fish tissue, humans consuming fish can potentially consume significant levels of mercury.We examined the concentration of total mercury in 6,806 fish, representing 108 species from 40 families. Species represented all major trophic groups, from primary consumers to apex predators.The majority of individuals we examined contained low concentrations of mercury, but concentrations in individual fish varied greatly within and among species. Species with very low mean or median mercury concentrations tended to be planktivores, detritivores, species that feed on invertebrates, or species that feed on invertebrates and small fish prey.Apex predators typically had the highest mercury concentrations. In most species, mercury concentration increased as fish size increased. Sampling in Florida waters is continuing, and future research relating mercury levels to fish age, feeding ecology, and the trophic structure of Florida’s marine and estuarine ecosystems will help us better understand concentrations of this element in marine fishes. (64pp.

The Relative Abundance and Feeding Habits of Juvenile Kingfish (Sciaenidae: Menticirrhus) in a Gulf of Mexico Surf Zone

We describe seasonal and diel occurrence patterns, density, dietary progressions, and trophic relationships of Menticirrhus littoralis, M. americanus and M. saxatitis collected from the Horn Island, Mississippi, surf zone. Menticirrhus littoralis was the most abundant species (62.7%), followed by M. americanus (21.8%) and M. saxatitis (15.5%). Densities were highest during spring and summer and decreased markedly during the winter. Species showed diel changes in abundance, with abundance increasing during dusk and dawn for M. littoralis, and during the day for M. americanus and M. saxatilis. All three species showed ontogenetic progressions in diet, with siphon tips from Donax spp., cumaceans and mysids being most important to smaller (\u3c80 mm SL) M. littoralis and M. americanus; cumaceans, mysids and amphipods were most important to smaller M. saxatitis. Larger individuals of all three species fed more on whole Donax, polychaetes, Emerita talpoida, brachyurans, and fishes. Both intra- and interspecific dietary overlap was greatest for the smaller size groups of juveniles and declined with growth. Dietary overlap between 20 mm size classes was greatest for intra- compared to interspecific comparisons

Early Life History of the Black Drum Pogonias cromis (Pisces: Sciaenidae) in Tampa Bay, Florida

The distribution, relative abundance, habitat, age, growth, and feeding habits of larval and juvenile black drum (Pogonias cromis) from Tampa Bay, Florida, are described. Spawning took place in the lower bay or nearshore Gulf waters from November through May, with the majority of spawning occurring in March. Spawning peaks often coincided with, but were not dependent on, the new or full moon and were seemingly influenced by tidal period. Most spawning occurred during rising temperatures and occurred earlier in Tampa Bay than in northern latitudes. Most larvae were collected during March and April, and more were found in incidental surface dip-net collections in Bayboro Harbor than from regular plankton-net collections in the bay. Larvae collected in the middle and upper bay were larger (2.9-7.3 mm) than those collected in the lower bay (1.8-5.8 mm). Plankton-net collections from midwater depths at the single night station and from bottom depths at the three day stations contained the majority of larval black drum. Juveniles 30-60 mm SL were abundant in May and June in rivers and tidal creeks with low to moderate salinities and unvegetated mud bottoms. At lengths \u3e100 mm SL, juveniles began dispersing throughout the bay. Ages determined from counting daily otolith rings agreed with ages determined by using length-frequency progressions and showed that black drum larvae had a growth rate of 0.2-0.3 mm/ day, whereas juveniles 35 to 150 mm grew 0.8-0.9 mm/day. Forty-eight percent of the larval stomachs examined were empty; stomachs with food contained primarily cope pods. Mollusks were the major food group in juvenile black drum stomachs; small (\u3c60 mm) juveniles consumed mainly bivalve siphon tips, whereas larger (\u3e75 mm) juveniles consumed more fish, bivalves, and gastropods

Effects of live-bait shrimp trawling on seagrass beds and fish bycatch in Tampa Bay, Florida

The use of live shrimp for bait in recreational fishing has resulted in a controversial fishery for shrimp in Florida. In this fishery, night collections are conducted over seagrass beds with roller beam trawls to capture live shrimp, primarily pink shrimp, Penaeus duorarum. These shrimp are culled from the catch on sorting tables and placed in onboard aerated “live” wells. Beds of turtlegrass, Thalassia testudinum, a species that has highest growth rates and biomass during summer and lowest during the winter (Fonseca et al., 1996) are predominant areas for live-bait shrimp trawling (Tabb and Kenny, 1969). Our study objectives were 1) to determine effects of a roller beam trawl on turtlegrass biomass and morphometrics during intensive (up to 18 trawls over a turtlegrass bed), short-term (3-hour duration) use and 2) to examine the mortality of bycatch finfish following capture by a trawl

An Input-output Model of the Lower Rio Grande Region of Texas

The Lower Rio Grande Region is composed of the nineteen southernmost counties in Texas. The major portion of the population of the region resides along the Rio Grande River in border communities and Corpus Christi on the Gulf of Mexico. The primary economic activities are crop production, ranching, shrimping, oil production, and commercial activities. The existence of social costs, in conjunction with a desire for increased economic development, created the need that led to the development of a regional Input-Output Model. The Input-Output Model consists of five tables. The Transactions Table was developed from primary and secondary data. The estimated transactions were adjusted to form a producer-price matrix. Both transportation charges and costs of goods sold were allocated to appropriate final demand sectors. The remaining four tables were derived from the Transactions Table. They include a Direct Coefficients Table, a Direct and Indirect Coefficients Table, a Labor Coefficients Table, and a table that closes the model with respect to the household (The Closed Model Table). The uses of the Input-Output tables are explained in relation to the historical problems that have arisen in the Lower Rio Grande Region. In addition, examples are given on how the model can be used to develop information for planning

Early Life History of the Snook, Centropomus undecimalis, in Tampa Bay, Florida

Data accumulated during four sampling programs and incidental sampling are used to describe the distribution, growth, range of hatching dates, and diet of juvenile snook, Centropomus undecimalis, from Tampa Bay, Florida. A total of 1,655 juvenile snook ranging from 10 to 346 mm SL were collected (72% \u3c70 mm SL). Small juveniles were common in small, quiet marshes, creeks, and lagoons, but their presence was not limited to areas with any single salinity range or vegetation type. Larger juveniles occupied similar habitats but were also found along more open bay and river shores. Length-frequency and otolith analyses were used to determine juvenile growth rates, which varied from 0.5 to 1.2 mm SL/day depending on the spawning date, size, and collection date. Growth data suggested that spawning took place from April until December, with peak spawning occurring in the summer (July to September). Juveniles \u3c45 mm SL fed mainly on copepods and mysids; larger fish switched to a diet of palaemonid shrimp and cyprinodontid and poeciliid fishes