J. Wesley Neal

Factors Influencing Tropical Island Freshwater Fishes: Species, Status, and Management Implications in Puerto Rico

Abstract Anthropogenic effects including river regulation, watershed development, contamination, and fish introductions have substantially affected the majority of freshwater habitats in Europe and North America. This pattern of resource development and degradation is widespread in the tropics, and often little is known about the resources before they are lost. This article describes the freshwater resources of Puerto Rico and identifies factors that threaten conservation of native fishes. The fishes found in freshwater habitats of Puerto Rico represent a moderately diverse assemblage composed of 14 orders, 29 families, and 82 species. There are fewer than 10 species of native peripherally-freshwater fish that require a link to marine systems. Introductions of nonindigenous species have greatly expanded fish diversity in freshwater systems, and native estuarine and marine species (18 families) also commonly enter lowland rivers and brackish lagoons. Environmental alterations, including land use and develo...

Stress Response and Posttransport Survival of Hybrid Striped Bass Transported with or without Clove Oil

Abstract A study was undertaken to determine whether stress responses and associated mortality in hybrid striped bass (white bass Morone chrysops × striped bass M. saxatilis) during and after transport could be mitigated by use of anesthesia with low concentrations of clove oil (10 μL/L of water) during transport. Stress indicators, including plasma cortisol, glucose, chloride (Cl−), sodium (Na+), potassium (K+), and calcium (Ca++) concentrations, were determined for hybrid striped bass sampled (1) initially from ponds, (2) after seining (45 min), (3) immediately after a 3-h transport, and (4) at 24 h posttransport (recovery); these values were compared with those of captive control fish. Fish anesthetized with clove oil during transport exhibited prolonged elevation of cortisol concentrations (124.3 ± 13.2 ng/mL, mean ± SE) at 24 h posttransport, while fish not exposed to anesthetic during transport recovered rapidly (to 34.1 ± 13.3 ng/mL) within 24 h. Plasma glucose concentrations in hybrid striped bass...

A Bioenergetics-Based Approach to Explain Largemouth Bass Size in Tropical Reservoirs

Abstract In tropical systems where largemouth bass Micropterus salmoides have been introduced, maximum age is reduced to the point where few fish live beyond 3 years and adult growth rates are very slow. Concurrently, tropical largemouth bass have an extended spawning period (up to 8 months) and individual fish spawn multiple times each year. In this study, we examined the relationship between latitude and maximum size (record angler-caught fish) of largemouth bass from temperate to tropical environments and tested the hypothesis that the slow growth of adult largemouth bass is the result of excessive energy reallocation to reproduction. State and national record-sized largemouth bass were plotted against latitude for the USA, Cuba, Dominican Republic, Japan, Portugal (European record), Mexico, and Puerto Rico. Largemouth bass maximum weight increased as latitude decreased from 46.8°N; peak maximum weight occurred at 27.9°N. Below 27.9°N, largemouth bass size records decreased as latitude decreased (R 2 =...

THE EFFECTS OF LARGEMOUTH BASS VIRUS ON A QUALITY LARGEMOUTH BASS POPULATION IN ARKANSAS

A 22.4-ha impoundment experienced an outbreak of Largemouth bass (Micropterus salmoides) virus (LMBV) disease in the summer of 2006. All dead or dying largemouth bass observed throughout the entire event were recorded and removed. In this study, we estimated mortality and examined size distribution, condition, and biomass following the outbreak. Boat-mounted electrofishing was used to collect largemouth bass for a mark-recapture population estimate and other population metrics. Fish samples were examined for evidence of LMBV, other infectious diseases, and physical abnormalities. Cell cultures inoculated with samples from moribund fish developed cytopathic effects typical of LMBV, and polymerase chain reaction (PCR) confirmed the presence of LMBV. The total number (N±95% confidence interval) of stock-size largemouth bass remaining was estimated to be 2,301±528 fish (103 bass/ha). The total observed mortality, including dead and dying individuals, during the LMBV outbreak was 176 largemouth bass (7% of the initial population). The total biomass remaining was estimated at 1,592 kg of stock-size bass and a relative biomass of 71.5 kg of stock-size largemouth bass per hectare. Largemouth bass size structure was dominated by quality and preferred (300–510 mm) size classes, with very few memorable-size or larger (>510 mm) fish, and the relative weight of largemouth bass was unusually variable. These results demonstrate that largemouth bass abundance and biomass in the reservoir remained very high despite mortalities attributed to a LMBV outbreak.

A Comparison of Larval Fish Sampling Methods for Tropical Streams

Abstract Assessment of early life history characteristics requires effective sampling methods for larval fishes. Different gears are suitable for different habitats and frequently select different sizes or life history stages. In this study, two passive sampling methods were compared for use in collecting larval freshwater and estuarine fishes in two tropical streams. Drift nets and light traps were identified a priori as the most appropriate gears for sampling in these systems based on stream characteristics (including accessibility, size, and morphology). Catches were compared between sampling methods. Additionally, catches under different environmental conditions (flow, tide stage, and moon phase), during different sampling periods (time of day and week of summer), and at different depths were compared using mixed-effects analysis of variance. A total of 2,156 fish were captured in 954 h of sampling. The significant (&agr; < 0.05) explanatory variables for total larval catch were stream, sampling method, week of summer, time of day, and moon phase. Eleven families were represented in the samples, with the families Gobiidae (n = 948), Eleotridae (n = 391), and Syngnathidae (n = 276) comprising 94.9% of the identifiable larvae collected. The variables that explained both the Gobiidae and Syngnathidae catches were gear, week of summer, and time of day. The Syngnathidae catch was highest in drift nets, but the Gobiidae catch was highest in light traps. Nighttime light trap sampling appeared to be the best overall technique for larval collection in these systems. However, a combination of light traps and drift nets would reduce the biases associated with size and species selectivity found for individual gears, and this approach would be preferable for sampling small tropical streams.

Evaluation of Proposed Speckled Peacock Bass Cichla temensis Introduction to Puerto Rico

AbstractSpeckled Peacock Bass Cichla temensis are being considered for introduction into Puerto Rico to provide sportfishing opportunities and biological control for invasive New World cichlids. The proposed introduction was evaluated by following the American Fisheries Society’s recommended seven-step approach to introducing nonnative fish. This paper documents the evaluation process, which included a rapid risk screening approach using the Fish Invasiveness Screening Kit (FISK) version 2 and a series of controlled experiments on prey selection, agonistic behavior, and competition. The overall FISK score was 6 with a certainty factor of 0.84, placing the introduction in the medium-risk category (0–18) for invasiveness. Many of the attributes elevating this species to the medium-risk designation were the same attributes desired during species selection, including generalist feeding behavior and large body size, which are required for predation on New World cichlids. In controlled experiments, Speckled Pea...

Comparison of Diploid and Triploid Largemouth Bass Growth and Maturation through Age 1 in Puerto Rico

Abstract Triploid largemouth bass Micropterus salmoides could be valuable both in sport fish management and in food fish production. This study compared the growth and reproductive development of diploid and triploid largemouth bass through age 1 in Lucchetti Reservoir, Puerto Rico. We produced and stocked 487 diploids and 477 triploids tagged with binary coded wire tags and recaptured these fish over 2 years. Growth rates, condition (relative weight (Wr)), and reproductive investment (gonadosomatic index (GSI)) were compared for diploid and triploid fish. Rates of mean daily growth did not differ between diploids (0.81 mm/d; SE = 0.07) and triploids (0.91 mm/d; SE = 0.09) as juveniles or overall through age 1. Diploid largemouth bass exhibited advanced reproductive development during age 1, while triploids did not. Mean GSI was higher for diploid females (mean = 1.98; SE = 0.81) than for triploid females (mean = 0.29; SE = 0.05), but male mean GSI did not significantly differ between the two groups. No d...

Genetic Composition of Largemouth Bass in Puerto Rico Reservoirs

AbstractThe Largemouth Bass Micropterus salmoides includes two recognized subspecies, the Northern Largemouth Bass (NLMB; M. salmoides salmoides) and the Florida Largemouth Bass (FLMB; M. salmoides floridanus), which can hybridize to produce introgressed Largemouth Bass (ILMB; NLMB × FLMB). Largemouth Bass were introduced into Puerto Rico by using source populations from unknown origins (1915), a natural intergrade zone (1946 and 1947; ILMB), and peninsular Florida (1957; FLMB). All subsequent supplemental stocking efforts used broodstock collected from reservoirs in Puerto Rico with an effort to preferentially propagate non-introgressed FLMB. Here, we document contemporary FLMB-specific alleles and genotypes, changes in allele frequencies over the last decade, and differences in size structure between genotypes of the FLMB and its hybrids (ILMB) in Puerto Rico. Among 12 island reservoirs, FLMB alleles were prevalent at rates similar to estimates from a decade earlier, and the proportion of FLMB alleles (...

Comparison of Pulsed Gastric Lavage and Acrylic Stomach Tubes for Sampling the Diet of Butterfly Peacock Bass

AbstractNonlethal techniques for sampling the stomach contents of fishes have been developed for a variety of fish species. The goal of this study was to determine whether pulsed gastric lavage or acrylic stomach tubes were more effective for extracting stomach contents from Butterfly Peacock Bass Cichla ocellaris, specifically which was least injurious, retrieved the greatest percentage of stomach contents, and was least biased. Pulsed gastric lavage was less injurious than stomach tubes, with bruising of the stomach wall the most common injury being observed. The mean percent of stomach contents removed by pulsed gastric lavage (70.0%) was greater than the percent removed by stomach tubes (57.2%). Both gears were less successful at removing contents from larger fish and had difficulties retrieving contents from fuller stomachs. Pulsed gastric lavage is the recommended method for sampling stomach contents from Butterfly Peacock Bass, as it is both less injurious and more effective than stomach tubes. How...

Comparison of Electrofishing and Gill Nets for Sampling Cichlid Species

AbstractIntroduced cichlid species are increasingly more common in tropical freshwater systems and expanding in range, often with negative consequences to receiving systems. To better understand, monitor, and manage these populations, investigators need improved cichlid sampling protocols. In this study, electrofishing and gill nets were compared for their effectiveness at collecting cichlid species during diel sampling in a Puerto Rico reservoir containing five cichlid species. Both gears were fished simultaneously during day and night periods in January and July. Species composition, species length frequencies, and overall cichlid catch per person-hour were compared. This study suggests that electrofishing, particularly at night, may be a more appropriate gear for sampling cichlid species in the littoral zone of reservoirs, as gill nets were more time intensive, had more variable catch rates, and exhibited considerable selectivity. Gill nets were highly selective for Red Devil Cichlid Amphilophus labiat...