Jeffrey E. Hill

Assessing Environmental DNA Detection in Controlled Lentic Systems

Little consideration has been given to environmental DNA (eDNA) sampling strategies for rare species. The certainty of species detection relies on understanding false positive and false negative error rates. We used artificial ponds together with logistic regression models to assess the detection of African jewelfish eDNA at varying fish densities (0, 0.32, 1.75, and 5.25 fish/m3). Our objectives were to determine the most effective water stratum for eDNA detection, estimate true and false positive eDNA detection rates, and assess the number of water samples necessary to minimize the risk of false negatives. There were 28 eDNA detections in 324, 1-L, water samples collected from four experimental ponds. The best-approximating model indicated that the per-L-sample probability of eDNA detection was 4.86 times more likely for every 2.53 fish/m3 (1 SD) increase in fish density and 1.67 times less likely for every 1.02 C (1 SD) increase in water temperature. The best section of the water column to detect eDNA was the surface and to a lesser extent the bottom. Although no false positives were detected, the estimated likely number of false positives in samples from ponds that contained fish averaged 3.62. At high densities of African jewelfish, 3–5 L of water provided a >95% probability for the presence/absence of its eDNA. Conversely, at moderate and low densities, the number of water samples necessary to achieve a >95% probability of eDNA detection approximated 42–73 and >100 L, respectively. Potential biases associated with incomplete detection of eDNA could be alleviated via formal estimation of eDNA detection probabilities under an occupancy modeling framework; alternatively, the filtration of hundreds of liters of water may be required to achieve a high (e.g., 95%) level of certainty that African jewelfish eDNA will be detected at low densities (i.e., <0.32 fish/m3 or 1.75 g/m3).

Survey of Ovaprim Use as a Spawning Aid in Ornamental Fishes in the United States as Administered through the University of Florida Tropical Aquaculture Laboratory

Abstract Ovaprim is a commercial product used as a spawning aid in fishes and contains a salmon gonadotropin-releasing hormone analog and a dopamine antagonist. Since 2005, the use of Ovaprim in commercial ornamental fish production has been through enrollment with the University of Florida Tropical Aquaculture Laboratory in an Investigational New Animal Drug (INAD) study. A database is maintained to provide information to the U.S. Food and Drug Administration on product effectiveness and target animal safety. There were 25 fish species in 17 genera and 10 families in the INAD database. Ostariophysan fishes constituted 84% of the species and 99.9% of the individuals. The goldfish Carassius auratus was numerically the dominant species (80% of individuals). Nearly 40,000 fish in total were injected with Ovaprim; ovulation was induced in 92% of females and spermiation was induced in 96% of males, primarily reflecting extensive use in cyprinid fishes. Conversely, average success rates across all species were ...

Issues Regarding the Use of Sedatives in Fisheries and the Need for Immediate-Release Options

Abstract The lack of an immediate-release sedative (i.e., one for which no postsedation holding or withdrawal period is required) jeopardizes fish and fisheries research and poses considerable risk to those involved in aquatic resource management and the operation of public hatcheries and commercial fish farms. Carbon dioxide may be used as an immediate-release sedative, but it is slow-acting and difficult to apply uniformly and effectively. Tricaine methanesulfonate (MS-222) is easier to apply but requires a 21-d withdrawal period. The lack of an immediate-release sedative approved by the U.S. Food and Drug Administration (FDA) is a consequence of numerous factors, including the complexities of the approval process, the substantial human and monetary resources involved, and the specialized nature of the work. Efforts are currently underway to demonstrate the safety and effectiveness of benzocaine- and eugenol-based products as immediate-release sedatives. However, pursuing approvals within the current fr...

Revisions of the Fish Invasiveness Screening Kit (FISK) for its application in warmer climatic zones, with particular reference to peninsular Florida.

The initial version (v1) of the Fish Invasiveness Scoring Kit (FISK) was adapted from the Weed Risk Assessment of Pheloung, Williams, and Halloy to assess the potential invasiveness of nonnative freshwater fishes in the United Kingdom. Published applications of FISK v1 have been primarily in temperate-zone countries (Belgium, Belarus, and Japan), so the specificity of this screening tool to that climatic zone was not noted until attempts were made to apply it in peninsular Florida. To remedy this shortcoming, the questions and guidance notes of FISK v1 were reviewed and revised to improve clarity and extend its applicability to broader climatic regions, resulting in changes to 36 of the 49 questions. In addition, upgrades were made to the software architecture of FISK to improve overall computational speed as well as graphical user interface flexibility and friendliness. We demonstrate the process of screening a fish species using FISK v2 in a realistic management scenario by assessing the Barcoo grunter Scortum barcoo (Terapontidae), a species whose management concerns are related to its potential use for aquaponics in Florida. The FISK v2 screening of Barcoo grunter placed the species into the lower range of medium risk (score = 5), suggesting it is a permissible species for use in Florida under current nonnative species regulations. Screening of the Barcoo grunter illustrates the usefulness of FISK v2 as a proactive tool serving to inform risk management decisions, but the low level of confidence associated with the assessment highlighted a dearth of critical information on this species.

Salinity Tolerance of the African Jewelfish Hemichromis letourneuxi, a Non-native Cichlid in South Florida (USA)

Abstract The African Jewelfish (Cichlidae: Hemichromis letourneuxi) is a predatory, non-native fish that has recently (since 2000) begun to expand its geographic range across south Florida. The salinity tolerance of H. letourneuxi was unknown, and thus it was unclear whether the species could use estuarine or coastal environments. The response of H. letourneuxi to chronic change in salinity was evaluated here by exposing fish to progressively increasing salinities (0–80 ppt). Fish were held at target salinities for a minimum of 30 days. The species showed excellent survival from 0–50 ppt. At 60 ppt, only 25% of the fish survived, and mean estimated survival time was 12 days. Above 60 ppt, mortality was 100%. Fish grew equally well from 0–50 ppt. In another experiment, fish were transferred directly from freshwater to various salinities from 5–35 ppt (seawater) and held for seven days, after which survivors were returned to freshwater. All fish transferred directly from freshwater to salinities up to 20 ppt survived; only 56% survived when transferred from freshwater to 25 ppt, and none survived transfer above 25 ppt. Experimental results indicated that H. letourneuxi can persist easily in salinities prevalent in coastal environments, even during periods of hypersalinity common in south Florida estuaries. Salinity will not restrict its dispersal by coastal pathways.

Effects of Tricaine Methanesulfonate, Hypno, Metomidate, Quinaldine, and Salt on Plasma Cortisol Levels following Acute Stress in Threespot Gourami Trichogaster trichopterus

Abstract Blood plasma cortisol concentration is an indicator of stress in fish, and anesthetics may serve to ameliorate stress and reduce the cortisol response. Previous studies have concentrated on cold- and warmwater species; little information exists for tropical fishes. Mortalities are increased after handling stress of threespot gourami Trichogaster trichopterus (Osphronemidae), a commonly cultured tropical ornamental fish. Plasma cortisol levels were evaluated in threespot gourami after a handling stressor and treatment with one of four anesthetics—tricaine methanesulfonate (TMS; 60 mg/L), metomidate (0.8 mg/L), quinaldine (5 mg/L), and Hypno (0.14 mg/L)—or salt (NaCl; 3 g/L). Fish in all anesthetic treatments had significantly lower cortisol levels than either salt-treated fish or the untreated controls. Therefore, the use of such anesthetics should be beneficial in reducing handling stress. Based on our data, further studies refining the use of anesthetics, particularly metomidate and quinaldine, ...

Fluorescent Transgenic Zebra Danio More Vulnerable to Predators than Wild-Type Fish

Abstract There is a knowledge gap in the ecological risk assessment of transgenic fish as to whether novel traits change their vulnerability to predation and thus their ability to establish themselves in nature. The U.S. commercialization of ornamental transgenic zebra danios Danio rerio and the approaching commercialization of other transgenic fish heighten the need for ecologically realistic models with which to address this question. Transgenic zebra danios with fluorescent body colors represent a good model system because marketed lines are likely to be released by hobby aquarists and it is relatively easy to study their interspecific interactions under nearly natural conditions. In experiments including habitat complexity, transgenic red-fluorescent-protein zebra danios were approximately twice as vulnerable as the wild type to predation by largemouth bass Micropterus salmoides and eastern mosquitofish Gambusia holbrooki, two native predators that potentially resist invasion by introduced fish. Incre...

Preliminary Observations of Topical Gill Application of Reproductive Hormones for Induced Spawning of a Tropical Ornamental Fish

Abstract Hormone injection is a common spawning induction technique in aquaculture but is of limited use in small species with low fecundity. An alternative to injection for such species is topical gill application. We conducted an experiment with female rainbow sharks Epalzeorhynchos erythrurus (Cyprinidae) in one control group and three treatment groups: (1) topical gill application of dimethyl sulfoxide (DMSO), (2) topical gill application of DMSO and Ovaprim, and (3) an Ovaprim intramuscular (IM) injection. Ovaprim contains a salmonid gonadotropin-releasing hormone analog and a dopamine antagonist. Fish were anesthetized, treated, and placed into recovery tanks. Fish were manually checked for ovulation by exerting abdominal pressure at 8, 10, and 11 h posttreatment and were observed for mortality during a 24-h period. Ovulation varied significantly: we found no ovulation of females in the control or DMSO groups, 78% ovulation in the DMSO plus Ovaprim group, and 100% ovulation in the Ovaprim IM injecti...

Investigational Use of Metomidate Hydrochloride as a Shipping Additive for Two Ornamental Fishes

During shipping, ornamental fish can be stressed due to handling, high stocking densities, and deteriorating water quality. Adding sedatives, such as metomidate hydrochloride, to shipping water may improve fish survival rates and the percentage of fish in saleable condition. Although the effects of metomidate hydrochloride on the stress response in fish have been studied, its application as a shipping additive has not been well investigated, particularly for tropical ornamental fishes shipped under industry conditions. Convict cichlids Cichlasoma nigrofasciatum and black mollies Poecilia sphenops were evaluated for 7 d after a 24-h period of exposure (including ground and air transport) to one of four metomidate hydrochloride concentrations: 0.0, 0.2, 0.5, and 1.0 mg/L. Immediate posttransport and cumulative mortality data, as well as 12-h and 7-d posttransport appearance and behavior scores, were generated. In convict cichlids, the highest dose of metomidate hydrochloride (1.0 mg/L) reduced mortality (0% compared with cumulative means of 5.5-9.2% in other groups) and increased the percentage of saleable fish (91.7% were immediately saleable compared with 12.5-50% in other groups). No effect was detected in black mollies at any concentration tested. Metomidate hydrochloride showed promise as a shipping additive for convict cichlids, but further studies are warranted to evaluate species-specific responses in other ornamental species.

National Aquatic Species Risk Analysis: A Call for Improved Implementation

Abstract There has been criticism of the risk analysis process used by federal agencies in the United States, the Generic Nonindigenous Aquatic Organisms Risk Analysis Review Process (Generic Analysis) developed by the Aquatic Nuisance Species Task Force (ANSTF). Although some criticism is justified, we argue that critics as well as federal agencies implementing the process have focused on in-house risk assessment and have ignored including stakeholders in a collaborative and integrated risk analysis implementation that consists of conceptually distinct risk assessment and risk management. Although the Generic Analysis approved by the ANSTF consisted of this design, there has been only a single collaborative effort that fully integrated risk assessment and risk management. Although risk assessment and risk management are distinct, they should not be conducted in isolation or without stakeholder involvement. We argue that when stakeholders are included and these processes are effectively linked, the Generi...