Joseph E. Serafy

Global overview of the major constituent-based billfish tagging programs and their results since 1954

Release and recovery files from the worlds five major constituent-based billfish (Istiophoridae) tagging programs were assembled into a single composite database. Data sources included the National Marine Fisheries Services (NMFS) Cooperative Tagging Center (MIA) in the Atlantic Ocean, the NMFSs Cooperative Billfish Tag- ging Program (LJA) in the Pacific and Indian Oceans, the Australian Cooperative Tagging Program in the Pacific and Indian Oceans, the New Zealand Cooperative Game Fish Tagging Program in the Pacific Ocean, and The Billfish Foundations (TBF) tagging program in the Atlantic, Pacific and Indian Oceans. Results for the main target species, including black marlin (Makaira indica), blue marlin (Makaira nigricans), white marlin (Tetrapturus albidus), striped marlin (Tetrapturus audax) and sailfish (Istiophorus platypterus) were compared and contrasted based on species, ocean body and tagging program. A total of over 317 000 billfish have been tagged and released, and 4122 have been recovered since 1954. Tag recovery percentages were generally higher for a recently developed double- barb nylon anchor tag compared with the typically used stainless steel dart tag. Greatest distances moved were largest for blue marlin and black marlin, followed by striped marlin, white marlin and sailfish. The TBF program had the highest tag recovery percentages for white marlin (2.4%) and blue marlin (1.7%), whereas the MIA program had the highest percentage recovery for sailfish (1.8%). The LJA program had the highest recovery percentages for black marlin (1.9%) and striped marlin (1.4%). The annual number of releases and recoveries for each tar- get species tended to increase over the time series, particularly during the last decade. Cyclic annual movement patterns and/or seasonal site fidelity were evident for black marlin and white marlin. The data suggest that tag recovery percentages can be affected by tag type, reporting rate, localized fishing activities, outreach activities, and a variety of logistical issues indirectly related to size of ocean body. The efficiencies of the tagging programs are compared and recommendations are made to improve the programs. The composite tagging database provides the opportunity for a more comprehensive evaluation of the data and tagging programs than has previously been pos- sible by examining the individual programs in isolation. The main advantage of constituent-based tagging programs is that large numbers of billfish can be tagged at a minimum cost. The main drawbacks are a lack of control over the tagging event and return of recovery data. Constituent-based tagging programs provide essential data on billfish movement and biology, and should be expanded and improved to meet the increasing need for this information.

Sustained high yields of Gracilaria (Rhodophyta) grown in intensive large-scale culture

Gracilaria ferox J. Agardh was grown continuously in large, outdoor tanks under a pulse-fed nutrient regime for four years. Productivity ranged from 21.4 to 59.2 g d. wt m−2 d−1 with a mean of 39.7 g d. wt m−2 d−1 over the entire study period. Because the cultures were maintained under non-nutrient limiting conditions, productivity was regulated primarily by seasonal changes in light and temperature, which accounted for 75% of the variability of growth in algal yields. Salinity ranged from 31.0 to 36.5‰ and had insignificant effects on growth within this range. The original vegetative strain was maintained over the entire study without the need for additional supplementation from field-collected stock. Because of the pulse-fed nutrient supply, epiphytic growth on the target species was negligible (< 3% total biomass) throughout the study. The yields attained in this study rank among the highest reported for any intensively managed photosynthetic crop and demonstrate the feasibility of growing red macroalgae like Gracilaria at a sustained high yield in a large-scale, land-based culture system.

An immunological study of predation on hatchery-reared, juvenile red drum (Sciaenops ocellatus, Linnaeus): description of an ELISA and predator-prey studies in nature

This report is a continuation of an on-going study to develop immunological methods for eventual use in determining the predation mortality of newly released, hatchery-reared red drum (Sciaenops ocellatus, Linnaeus). Using a specific goat antiserum produced to a purified 80 kDa red drum glycoprotein, we detected the glycoprotein routinely in soluble extracts of red drum by Western blots. To supplement the immunoblotting, we proceeded to develop a highly sensitive and specific ELISA (enzyme-linked immunosorbent assay). The major problem in developing the ELISA was defining conditions to eliminate a natural inhibitor in soluble extracts of red drum that prevented the 80 kDa protein from binding to microtiter plates. The technical difficulties for a successful ELISA were resolved by adjusting extracts to pH 4.7 and 0.3 M NaCl, based on conditions developed for purification of the 80 kDa protein on a cationic-exchange gel by fast protein liquid chromatography (FPLC). The defined parameters eliminated the inhibition and resulted in optimal binding of the glycoprotein to the polymer surface of plates for ELISA. Approximately 10 h after the release of tens of thousands of red drum fingerlings at two sites in Biscayne Bay, FL, USA, a center-bag haul seine was used to sample the fish and capture predators. Two species, Sphyraena barracuda (Walbaum), great barracuda, and Strongylura notata (Poey), redfin needlefish, were the major predators. ELISA and Western blots were used to identify visually difficult or unidentifiable Sciaenops ocellatus in gut contents of the predators. Based on nine samples from seven Strongylura notata, and 10 samples from eight Sphyraena barracuda, 100% of the samples were identified as red drum in the needlefish and 50% in the great barracuda. These studies confirm the feasibility of using immunological methods to identify otherwise unidentifiable prey in gut contents of predators in nature.

An Efficient Sampling Survey Design to Estimate Pink Shrimp Population Abundance in Biscayne Bay, Florida

Abstract We developed an efficient sampling design-based approach using fishery-independent surveys to estimate population abundance of pink shrimp Penaeus duorarum over time in Biscayne Bay, Florida. We initially implemented quarterly stratified random sampling (StRS) using nine habitat strata and determined that average pink shrimp density (numbers/m2) was highest in late fall and lowest in spring and late summer. Coefficient of variation of the quarterly surveys, expressed as percent standard error/mean density, ranged from 5.8% to 14.3%. We found StRS to be more efficient (i.e., with lower variance) than simple random sampling (SRS) in most seasons. Statistical analyses suggested that pink shrimp densities were dependent on the biophysical habitat variables of bottom substrate, depth, and salinity. We also noted ontogenetic shifts in these relationships that were particularly pronounced at the onset of sexual maturation. Poststratification analysis was used to further evaluate several alternative habi...

Evidence of blue marlin, Makaira nigricans, spawning in the vicinity of Exuma Sound, Bahamas

Exuma Sound is a semi-enclosed body of water bounded by islands of the Bahamas. During July 2000, sampling for larval billfish was carried out throughout the Sounds surface waters as well as in adjacent open waters of the Atlantic Ocean. A total of 99 larval billfish (Istiophoridae) was collected. Ninety of the larvae were identifiable as blue marlin (Makaira nigricans) and three as sailfish (Istiophorus platypterus). The remaining larvae were also istiophorids, unidentified to species owing to damage; no larval Xiphias gladius were collected. Larval blue marlin densities ranged from 0 to 3.4 larvae/1000 m 2 ; their sizes ranged from 3.1 mm notochord length to 22.6 mm standard length. Densities tended to be highest north-east of the Sounds central axis, especially within the two regions where exchange with the Atlantic is greatest. Mean densities tended to decrease in the direction of mean flow; mean lengths increased from 8.08 mm at the Sounds mouth to 14.7 mm standard length at its upper reaches. Length-based estimates of larval age ranged from 2.2 to 17.2 days. Given these age estimates and assuming passive surface transport, the blue marlin larvae collected were likely the result of recent spawning in waters that include Exuma Sound and may extend some 200 km south-east of its mouth. This study suggests that Exuma Sound functions as a nursery area for blue marlin, and possibly other billfish species, at least during the summer. Limited sampling just outside Exuma Sound, in the Atlantic Ocean proper, also yielded blue marlin larvae.

Density-habitat relationships of mangrove creek fishes within the southeastern saline Everglades (USA), with reference to managed freshwater releases

The Comprehensive Everglades Restoration Plan aims to make considerable changes to the quantity, quality, and timing of freshwater delivery to the southeastern saline Everglades (SESE), a mangrove ecosystem located between the freshwater Everglades and downstream estuarine embayments. Whereas fishes inhabiting seasonally-inundated areas of the SESE and the shorelines of downstream embayments have been examined, those utilizing the creeks connecting these ecotones have not. To evaluate the functional role of the creek habitat and the possible impact of future hydrologic changes on the fishes inhabiting them, 228 underwater visual surveys were performed at three locations of the SESE over a three-year period. Fish abundance data was related to structural habitat, water level, and salinity over various time periods. The SESE contains taxa from both the freshwater Everglades and downstream embayments, but does not appear to function as a nursery for most fishery taxa. Abiotic variability and fish diversity increased with distance from major freshwater sources. Though there were significant differences in the physical structure of mangrove trees among locations, few meaningful correlations between these parameters and the density of individual fish taxa were found. Small ‘prey-base’ fishes (<10 cm TL) utilize the expansive ephemeral wetlands (i.e., upper mangle) during wet periods, and were concentrated into deeper creeks when these wetlands became dry. Densities of these fishes increase on the upper mangle with increased flooding (hydroperiod), and we observed greater densities of larger species in the creeks when hydroperiods exceeded 240 days. Based on these results, we recommend that water management create water releases which result in a wet period of ca. 240 days, followed by a gradual dry period lasting ca. 90 days.

Geospatial Video Monitoring of Nearshore Benthic Habitats of Western Biscayne Bay (Florida) Using the Shallow-Water Positioning System (SWaPS)

Abstract The nearshore habitats of western Biscayne Bay, a shallow lagoon adjacent to the city of Miami, are influenced by salinity fluctuations caused by freshwater discharges from canals. Benthic communities in these susceptible littoral habitats have been underrepresented in monitoring programs because of the difficulties associated with boat access. In the present study, we implement a geospatial video-based survey technique, the shallow-water positioning system (SWaPS), to document the abundance and distribution of benthic organisms in these shallow habitats. Mounted on a shallow-draft vessel, SWaPS integrates a global positioning system receiver with a video camera such that each video frame recorded is stamped with position information, date, water depth, heading, and pitch and roll. The georeferenced digital frames collected can be easily analyzed to document patterns of abundance and distribution of submerged aquatic vegetation and other benthic organisms. The field surveys conducted using SWaPS showed that species distributions are influenced by their respective tolerances to salinity patterns. Seagrass species with relatively high tolerance for low, variable salinity (e.g., Halodule wrightii and Ruppia maritima) tend to have high abundance only in areas influenced directly by canal discharges, while species with relatively limited tolerance for low salinity (e.g., Thalassia testudinum) tend to increase in abundance with increasing distance from the mouths of canals. The use of video-based surveys with high spatial precision facilitates rapid, cost-effective, and repeatable monitoring of shallow marine benthic communities. The most attractive features of this system are (1) the ability to cover large areas rapidly without divers and (2) the ability to return to precise locations without establishing permanent markers (e.g., stakes). Moreover, the georeferenced digital images collected with SWaPS are a valuable permanent visual archive that can provide the baseline information needed to evaluate long-term patterns of change in environments such as western Biscayne Bay that are subject to increasing pressure from human activities.

Allometry of the Growth of Pink Shrimp Farfantepenaeus duorarum in a Subtropical Bay

Abstract We developed robust allometric relationships for pink shrimp Farfantepenaeus (=Penaeus) duorarum by focusing on appropriate mathematical models and statistical procedures for parameter estimation. We utilized fishery-independent data on the abundance and size of juvenile and subadult pink shrimp from an efficient sampling program in Biscayne Bay, Florida. Total length (TL), carapace length (CL), and wet weight (W) were obtained from 440 male and 487 female pink shrimp ranging from 3 to 30 mm CL. The TL−CL function was linear. Because we noticed a pronounced shift in the relationship at the onset of sexual maturity, however, we estimated separate models for juveniles (CL < 18 mm; TL = 1.616 + 4.503·CL) and subadults (CL ≥ 18 mm; TL = 11.636 + 3.985·CL). The dependence of W on CL was best described by nonlinear allometric functions of the form W = αCLβ. Model parameters were estimated by least-squares regression methods after log-transformation of the original nonlinear power function. The allometr...

Mangroves enhance reef fish abundance at the Caribbean regional scale

Several studies conducted at the scale of islands, or small sections of continental coastlines, have suggested that mangrove habitats serve to enhance fish abundances on coral reefs, mainly by providing nursery grounds for several ontogenetically-migrating species. However, evidence of such enhancement at a regional scale has not been reported, and recently, some researchers have questioned the mangrove-reef subsidy effect. In the present study, using two different regression approaches, we pursued two questions related to mangrove-reef connectivity at the Caribbean regional scale: (1) Are reef fish abundances limited by mangrove forest area?; and (2) Are mean reef fish abundances proportional to mangrove forest area after taking human population density and latitude into account? Specifically, we tested for Caribbean-wide mangrove forest area effects on the abundances of 12 reef fishes that have been previously characterized as “mangrove-dependent”. Analyzed were data from an ongoing, long-term (20-year) citizen-scientist fish monitoring program; coastal human population censuses; and several wetland forest information sources. Quantile regression results supported the notion that mangrove forest area limits the abundance of eight of the 12 fishes examined. Linear mixed-effects regression results, which considered potential human (fishing and habitat degradation) and latitudinal influences, suggested that average reef fish densities of at least six of the 12 focal fishes were directly proportional to mangrove forest area. Recent work questioning the mangrove-reef fish subsidy effect likely reflects a failure to: (1) focus analyses on species that use mangroves as nurseries, (2) consider more than the mean fish abundance response to mangrove forest extent; and/or (3) quantitatively account for potentially confounding human impacts, such as fishing pressure and habitat degradation. Our study is the first to demonstrate at a large regional scale (i.e., the Wider Caribbean) that greater mangrove forest size generally functions to increase the densities on neighboring reefs of those fishes that use these shallow, vegetated habitats as nurseries.

Larval growth, development, and survival of laboratory-reared Aplysia californica: Effects of diet and veliger density

Over the last three decades, the California sea hare, Aplysia californica, has played an increasingly important role as a model organism in the neurosciences. Since 1995, the National Resource for Aplysia has supported a growing research community by providing a consistent supply of laboratory-reared individuals of known age, reproductive status, and environmental history. The purpose of the present study was to resolve the key biological factors necessary for successful culture of large numbers of high quality larval Aplysia. Data from a sequence of five experiments demonstrated that algal diet, food concentration, and veliger density significantly affected growth, attainment of metamorphic competency, and survival of Aplysia larvae. The highest growth and survival were achieved with a mixed algal diet of 1:1 Isochrysis sp (TISO) and Chaetoceros muelleri (CHGRA) at a total concentration of 250 x 10(3) cells/mL and a larval density of 0.5-1.0 per mL. Rapid growth was always correlated with faster attainment of developmental milestones and increased survival, indicating that the more rapidly growing larvae were healthier. Trials conducted with our improved protocol resulted in larval growth rates of >14 microm/day, which yielded metamorphically competent animals within 21 days with survival rates in excess of 90%. These data indicate the important effects of biotic factors on the critical larval growth period in the laboratory and show the advantages of developing optimized protocols for culture of such marine invertebrates.