Red Hind Research Articles

Sex structure and potential female fecundity in a Epinephelus guttatus spawning aggregation: applying ultrasonic imaging

Ultrasonic imaging was used to determine the spawning population structure and develop a fecundity estimation model for a red hind Epinephelus guttatus spawning aggregation within the Red Hind Bank Marine Conservation District, St Thomas, U.S.V.I. The spawning population showed considerable within‐month and between‐month variation in population size‐ and sex‐structure. In the spawning season studied, males appeared to arrive at the aggregation site first in December although females represented a large proportion of the catch early in the aggregation periods in January and February. Spawning occurred in January and February, and size frequency distributions suggested that an influx of small females occurred during the second spawning month. An overall sex ratio of 2·9 : 1 (female : male) was recorded for the whole reproductive season. The sex ratio, however, differed between months and days within months. More females per male were recorded in January than in February when the sex ratio was male biased. Fecundity estimates for this species predicted very high potential fecundities (2·4 × 105−2·4 × 106 oocytes). The ultrasound model also illustrated a rapid increase in potential female fecundity with total length. Ultrasonic imaging may prove a valuable tool in population assessment for many species and locations in which invasive fishing methods are clearly undesirable.

Population characteristics of a recovering US Virgin Islands red hind spawning aggregation following protection.

Many species of groupers form spawning aggregations, dramatic events where 100s to 1000s of individuals gather annually at specific locations for reproduction. Spawning aggregations are often targeted by local fishermen, making them extremely vulnerable to over fishing. The Red Hind Bank Marine Conservation District located in St. Thomas, United States Virgin Islands, was closed seasonally in 1990 and closed permanently in 1999 to protect an important red hind Epinephelus guttatus spawning site. This study provides some of the first information on the population response of a spawning aggregation located within a marine protected area. Tag-and-release fishing and fish transects were used to evaluate population characteristics and habitat utilization patterns of a red hind spawning aggregation between 1999 and 2004. Compared with studies conducted before the permanent closure, the average size of red hind increased mostly during the seasonal closure period (10 cm over 12 yr), but the maximum total length of male red hind increased by nearly 7 cm following permanent closure. Average density and biomass of spawning red hind increased by over 60% following permanent closure whereas maximum spawning density more than doubled. Information from tag returns indicated that red hind departed the protected area following spawning and migrated 6 to 33 km to a ca. 500 km(2) area. Protection of the spawning aggregation site may have also contributed to an overall increase in the size of red hind caught in the commercial fishery, thus increasing the value of the grouper fishery for local fishermen.

The habitats exploited and the species trapped in a Caribbean island trap fishery

We visually observed fish traps in situ to identify the habitats exploited by the U.S. Virgin Islands fishery and to document species composition and abundance in traps by habitat. Fishers set more traps in algal plains than in any other habitat around St. John. Coral reefs, traditionally targeted by fishers, accounted for only 16 % of traps. Traps in algal plain contained the highest number of fishes per trap and the greatest numbers of preferred food species. Traps on coral reefs contained the most species, 41 of the 59 taxa observed in the study. Acanthurus coeruleus was the most abundant species and Acanthuridae the most abundant family observed in traps. Piscivore numbers were low and few serranids were observed. Traps in algal plain contained the most fishes as a result of: ecological changes such as shifts in habitat use, mobility of species and degradation of nearshore habitat (fishery independent); and, catchability of fishes and long-term heavy fishing pressure (fishery dependent). The low number of serranids per trap, dominance of the piscivore guild by a small benthic predator, Epinephelus guttatus, and dominance of trap contents overall by a small, fast-growing species of a lower trophic guild, Acanthurus coeruleus, all point to years of intense fishing pressure.

Evaluation of a conservation strategy: a spawning aggregation closure for red hind, Epinephelus guttatus, in the U.S. Virgin Islands

Many tropical reef fishes spawn in large aggregations, which are readily targeted by fishers. By the 1980s, at least two grouper spawning aggregations were eliminated by intensive fishing off the island of St. Thomas, U.S. Virgin Islands, and another aggregating species, red hind, was intensively targeted. By 1988, the average length of red hind had greatly decreased to 295 mm, and the sex ratio was extremely skewed to 15 females per male, suggesting a heavily fished stock. Since this species is a protogynous hermaphrodite, the loss of large individuals (primarily males) could potentially result in sperm limitation in spawning aggregations. In 1990, a spawning aggregation closure was implemented. By 1997, average size of red hind had increased to 395 mm and sex ratio had shifted to 4 females per male. Fish were observed aggregating only in structurally complex habitat along the insular shelf edge. This habitat type is apparently not common along most of the shelf edge off St. Thomas and may provide shelter while reducing risk of predation during aggregation periods. These data suggest that protection of spawning aggregations is a sound management strategy with considerable potential for aiding the sustainable use of reef fish resources.

Gag (Mycteroperca microlepis) vitellogenin: purification, characterization and use for enzyme-linked immunosorbent assay (ELISA) of female maturity in three species of grouper

Circulating levels of the egg yolk precursor protein, vitellogenin (VTG), can be used as a biochemical indicator of maturation in female fish. Here we report on purification and partial characterization of VTG from a temperate marine serranid, the gag(Mycteroperca microlepis). Development of a competitive, enzyme-linked immunosorbent assay (ELISA) for gag VTG (gVTG) is also described. The gVTG was purified by DEAE-agarose anion exchange chromatography from a pooled plasma sample collected from several juvenile gag after they were injected with 17βestradiol. The protein appeared as a major band of Mr≅183 000 after SDS-PAGE ± Western blotting using either a specific rabbit antiserum to gVTG or a universal monoclonal antibody for vertebrate VTGs. Amino acid composition analysis and N-terminal peptide sequencing verified that gVTG is similar in primary structure to VTG from several other teleost species. The purified gVTG and its specific antiserum were used to develop a sensitive, competitive, antibody-capture ELISA for quantifying the protein in blood plasma from maturing females. VTG levels in maturing female gag were highly correlated with oocyte growth and circulating testosterone and 17β-estradiol levels, whereas VTG was non-detectable in juveniles, immature females or males. Two size-based maturity schedules for female gag were constructed, one utilizing detection of VTG in their circulation as a marker of maturity and the other relying on histological evidence that their ovaries were in vitellogenic or later stages of maturation. The two schedules were virtually identical. The gVTG ELISA was also used to detect VTG in blood plasma from mature Nassau grouper (Epinephelus striatus) and red hind (E. guttatus). As with gag, the assay was completely reliable for discriminating between reproductively mature females versus males from these two grouper species.

Scaling of skeletal mass to body mass in fishes.

The few available observations are consistent with the supposition that the relative weightlessness of fishes leads to isometric scaling of skeletal mass to body mass. To explore further this pattern we studied scaling in ontogeny with freshwater tilapia, Oreochromis nilotica, and in phylogeny with adult coral reef fishes. Body mass and skeletal mass were measured for freshly caught fishes. Data were transformed to logarithms and fitted to a power function with least-square linear regression. Whereas slope for all O. nilotica combined was consistent with isometry (b = 1.00; 95% CI = 0.02), slopes calculated separately for juveniles (b = 1.16; CI = 0.07) and adults (b = 1.10; CI = 0.07) indicated positive allometric scaling of the skeleton during ontogeny. The scaling pattern was isometric for a multispecies sample of perciform fishes from coral reefs (b = 0.82; CI = 0.21). However, the single perciform species with the largest number of individuals in the sample, Epinephelus guttatus, was positively allometric (b = 1.13; CI = 0.12), whereas the tetraodontiform, Balistes vetula, was isometric (b = 1.05; CI = 0.12). Instead of leading to isometry, weightlessness may increase the range of possibilities for the scaling of skeleton mass to body mass in fishes compared to terrestrial vertebrates. The scaling of the skeleton in fishes may be related to foraging style and manner of locomotion in water rather than be driven by the need to resist gravity. © 1996 Wiley-Liss, Inc.

Elemental Patterns in Red Hind (Epinephelus guttatus) Otoliths from Bermuda and Puerto Rico Reflect Growth Rate, Not Temperature

Sodium, sulfur, calcium, and strontium concentrations were measured (with an electron microprobe) across sectioned wild red hind (Epinephelus guttatus) otoliths from Puerto Rico and Bermuda. A single inverse relationship between strontium/calcium (Sr/Ca) ratios and log body growth rate describes the data from both localities. Patterns in Sr/Ca ratios have been used to infer temperature histories of individual fish; our data indicate that there is not a single Sr/Ca-temperature relationship capable of yielding a plausible temperature history across a single otolith, nor is there one that could give reasonable temperature histories for both the Puerto Rico and Bermuda otoliths. Previous findings of Sr/Ca–temperature relationships could be the result of body growth rate being correlated with temperature.

Size, Composition, and Spatial Structure of the Annual Spawning Aggregation of the Red Hind, Epinephelus guttatus (Pisces: Serranidae)

Annual spawning aggregations of the red hind, Epinephelus guttatus, occurring at the time of full moon in Jan., were surveyed off the southwest coast of Puerto Rico between 1983 and 1989. One aggregation in 1984 measured 70 x 140 m and contained a fish density that increased over a period of four days to a maximum of 7.6 fish per 100 m2 on the day of the full moon and then declined over two subsequent days. The female-to-male sex ratio was 5.6 for samples of fish speared on the bottom and 7.1 for those caught from the surface on hookand-line. This difference is not significant. Within the aggregation, fish formed clusters of two to seven individuals. Speared clusters contained either one male and two to three females or all females. In a 1986 aggregation, the dispersion pattern of all individuals within a large grid was evaluated with nearest-neighbor analysis. During the first two days of the aggregation, fish were distributed randomly. In the final three days, which included the day of full moon and the period when individuals probably spawned, fish were significantly clumped. This statistical pattern of clumping confirmed divers' impressions of fish in clusters, suggesting that spawning is not random but occurs in clusters containing one male and a few females. These results suggest that aggregations function primarily to enable males and females to find mates.

Neobenedenia pargueraensis n. sp. (Monogenea: Capsalidae) from the Red Hind, Epinephelus guttatus, and Comments about Neobenedenia melleni

Neobenedenia pargueraensis n. sp. from Epinephelus guttatus of Puerto Rico differs from all known species in possessing scoop-shaped accessory sclerites with pointed tips. It is most similar to Neobenedenia melleni and Neobenedenia longiprostata but differs from the former in having a fenestrate ovary and from the latter in that the ducts of the accessory glands are short, terminating just anterior to the vitelline reservoir rather than reaching the caudal end of the body. It differs from both species in having smooth rather than lobate testes. Neobenedenia melleni occurs throughout the tropical and subtropical western North Atlantic including Bermuda. It kills aquarium and aquaculture fishes with massive infestations and is a severe restraint on the culture of tilapia in sea water in the Caribbean.

Chromosome banding and genome compartmentalization in fishes

We have investigated the correlation between chromosome banding and compositional compartmentalization of the genome in three selected fish species, Anguilla anguilla (Anguilliformes), Epinephelus guttatus (Perciformes), and Labeo bicolor (Cypriniformes). These species were selected because they provided a spectrum of such compartmentalizations. Indeed, the band profiles in CsCl density gradients of the corresponding DNAs are characterized by a high compositional heterogeneity and a strong asymmetry for A. anguilla and by a very low compositional heterogeneity and a very weak asymmetry for E. guttatus. L. bicolor DNA shows an intermediate situation. — Chromosomes were studied using three consecutive stainings of the same mitoses. The intensity and reciprocity of the patterns obtained after Q- and R-banding were relatively strong for A. anguilla, whereas essentially no banding was found for E. guttatus. L. bicolor exhibited a chromosome banding of intermediate intensity and reciprocity. There is therefore a parallelism between chromosome banding and compositional compartmentalization of the genome. This finding provides new, independent support for previous indications of a correlation between these two properties.

Slowed motion analysis of stridulation in the grasshopper, Xanthippus corallipes (Acrididae: Oedipodinae)

Sounds were produced by male Xanthippus corallipes (Haldeman) during courtship by rubbing a ridge on the inside of the hind femur against a linear series of nodes on a raised forewing vein. The visual component included the motion of the hind femur exhibiting its bright coral-red medial surface and the red hind tibia as a semaphore. Analysis of ultra-high-speed motion films, video tapes with synchronized oscillotrace, sonagrams, and oscillograms showed that the two femora were consistently out of phase with one another during a single up–down motion of the chirp, the signal of one modulating that of the other. The resulting sound significantly differed from that produced by only one femur. A buzz produced only by vibration (almost 70 up–down motions per second) of a single femur. Different signals may be caused also by the use of different portions of the file having different nodal densities.Xanthippus corallipes is noted for the frequent occurrence of distinctive-appearing populations. Comparison of X. c. corallipes, the subspecies used here, with a published report on X. c. pantherinus (Scudder), revealed striking differences in the color of the femoral medial surface and in signalling sequences during courtship.

Utilization of Food by a Bermuda Reef Fish, Epinephelus guttatus

Utilization of Food by a Bermuda Reef Fish, Epinephelus guttatus