RESTORATION SUCCESS CRITERIA BASED ON PREVALENCES OF ABNORMALITIES IN FISH February 6, 1997
Team members are Joan A. Browder (team leader), Nancy P. Gassman, Michael C. Schmale, and Carl Sindermann. Collaboration was mainly by phone discussions rather than meetings. Most of the discussions occurred during January and February of 1996. The present update was prepared to include some relevant new information.
Morphological abnormalities are usually found at low prevalence in wild fish populations (Dawson and Heal 1975). For instance, Dahlberg (1970) examined 20,654 fish in Georgia estuaries and found only 12 with anomalies. High prevalences of skeletal abnormalities in fish are most often found where there is environmental contamination (Ziskowski et al. 1980, Mehrle el al. 1982, Slooff 1982, Bengtsson et al. 1985, Mayer et al. 1988). Fournie et al. (1996) found that gross pathological abnormalities of all types are most prevalent at sites with high sediment contaminant concentrations. PCBs, other chlorinated hydrocarbons, and some heavy metals have been associated with skeletal deformities in laboratory studies (Valentine & Soule 1973, Weis & Weis 1989). Laboratory studies have demonstrated that various gross pathological disorders can be induced by exposure to contaminants such as PCBs, petroleum products, and pesticides (Fournie et al. 1996). Huggett et al. (1992) considered skeletal abnormalities to be a "gross index" useful for assessing contaminant impact. Bengtsson et al. (1985) used skeletal deformities in fish to monitor pollution effects in the Baltic Sea.
Morphological abnormalities and other anomalies have been observed in Biscayne Bay by Skinner and Kandrashoff(1988), Browder et al. (1993), Gassman et al. (1994), and Schmale (1996). Scale disorientation (also called Kandrashoff's syndrome) and missing or deformed dorsal fin spines were the most common abnormalities observed in recent studies (Browder et al. 1993, Gassman et al. 1994, and Schmale 1996). Prevalences of dorsal fin abnormalities in Biscayne Bay were as high as 3% in bluestriped grunt and silver porgy and as high as 5% in sea bream and gray snapper in commercial catches reported in Browder et al. (1993). Gassman et al. (1994) reported finray deformity prevalences from 0.6% to 4.6% in sea bream (Archosargus probatocephalus), pinfish (Lagodon rhomboides), bluestriped grunt (Haemulon sciurus), white grunt (Haemulon plumieri), and gray snappers (Lutyanus griseus) and scale disorientation prevalences from 1.1% to 3.8% in sea bram, pinfish, bluestriped grunt, gray snapper, and Bermuda chub (Kyphosis sectatrix). A later study, which focused on sub-adults of the five species exhibiting finray deformities, found prevalences greater than 10% in Biscayne Bay (Schmale 1996).
Biscayne Bay sediments contain a variety of organic and metal contaminants at some locations (Corcoran 1983, Corcoran et al. 1983, 1984). Gassman et al. (1994) found that areas with higher total and aromatic hydrocarbons had higher levels of deformities. The prevalence of deformities in blue striped grunts was correlated with copper concentrations in sediments.
Both finray deformities and scale disorientation also have been found repeatedly in fish in the St. Lucie-Indian River Estuarine System (W. Kandrashoff, pers. comm.). These two abnormalities are relatively easy to spot, once the observer knows what to look for, and many fish can be screened for them quickly.
The prevalence of externally visable morphologic abnormalities in fish is suggested as the basis for developing indices of ecological health in South Florida estuaries. Scale disorientation and missing or deformed dorsal fin spines or rays, sometimes co-occurring with a concavity in the dorsal profile, are two abnormalities present in relatively high prevalences (e.g., up to about 20%) in several fish species at several locations in Biscayne Bay. Initially, an annual index should be computed for Biscayne Bay. The success criteria would be "a reduction in prevalences of abnormalities in fish species presently displaying high abnormalities." If local exploratory sampling warrants, an index based on prevalence of deformities should be computed for other South Florida estuaries. The presence of abnormalities in fish in the St. Lucie-Indian River Estuarine System is already documented. An ecological index should also be developed for the St. Lucie-Indian River Estuarine System.
Prevalences, by species and size class, for the sampling period 1993-1994 have been reported by Schmale (1996). These results could serve as the baseline.
Historic prevalences for Biscayne Bay are not known, however, the same fishermen who noticed the deformities in the Bay in the 1980s had been fishing in the Bay since the 1970s. Gassman et al. (1994) used sampling results from parts of Biscayne Bay having low prevalence rates to establish background levels of deformities of each type. iites where they found the lowest rates were Cape Florida Channel (CFC) and Caesar's Creek (CRC).
Prevalences of deformities at the recommended monitoring sites on the western side of the Bay should be reduced to at least the background level for the Bay, as indicated from measurements in Cape Florida Channel, in order to indicate a successful restoration. "Background" levels also may decline if restoration efforts reduce contaminant loads to Biscayne Bay and the movement of contaminated bottom sediments into the Bay.
In Biscayne Bay, prevalence should be measured in trawl catches from a chartered bait shrimp boat, corresponding to the procedure of Schmale (1996). Total counts and counts of fish with each abnormality would be made for five fish species-sea bream (Archosargus rhomboidalis), pinfish (Lagodon rhomboides), blue-striped grunt (Haemulon sciurus), white grunt (Haemulon plumeri), and gray snapper (Lutyanusgriseus). Prevalences (fish with anomaly/total fish of species) for each species would be calculated for the total sample and by class class. The index may be simplified to include only the principal size classes that are consistently present in the samples at a given location and time of the year.
Three locations--Biscayne Canal, Matheson Hammock, and Little River--were selected for developing the success criteria because, ofthe eight Schmale (1995) locations, these three had relatively high prevalences of deformities and, because of their proximity to canal discharge points, would be most likely affected by changes in the management of the C&SF Project and other regional-scale management changes (e.g., changes in pesticide application rates or contaminant discharges). In addition, a trawlable station should be established near the Cape Florida Channel station where Schmale (1995) found the lowest overall prevalence of abnormalities. This station should be monitored to maintain a current estimate of the background level of deformities in the Bay.
Sampling should take place twice a year, March and September. This would maximize the number caught of all five species and the representation of both juveniles and adults in the catches. In March, many young juveniles of pinfish, seabream, and grunts are present in the Bay. Adult gray snapper also are present at that time. In September, young juvenile gray snapper are found in the Bay, along with adults of pinfish, seabream, and grunts.
An equation such as the following might be used to establish an index that ranges from O to 1 to show improvement or from 1-1.0/baseline (a negative number that could potentially be greater than -1) to show further decline.where M=month, S=species, L=location, P94 = associated prevalence x 10, from Schmale (1996), and P96 = measured associated prevalence x 10 for 1996.
An important need is for laboratory studies testing the effect of contaminants on fish development. The studies should be focused on the petroleum products, pesticides, and heavy metals in use in South Florida, particularly those found in sediments of Biscayne Bay and other estuaries of this region. Bioassays of sediments for mutagenicity also would be useful.
A similar index should be developed for the St. Lucie-Indian River Estuary, where Walter and Michael Kandrashoff have found fish anomalies to be common at some sites. Scale disorientation and deformed or missing dorsal fins, the same two deformities prominent in Biscayne Bay fish, have also been found in the St. Lucie-Indian River system, as have miniature tail, anterior dorsal hump, and other skeletal deformities. Other abnormalities found in fish in this estuarine system include hemorrhages, ulcerations, fin erosion, tumors, and lesions. The presence of contaminants such as mercury and chlorinated hydrocarbons in sediments of the St. Lucie- Indian River Estuary is well established (Haunert 1988, Trefry et al. 1990, Trefry et al. 1992).
Data required for computing an ecological index based on prevalences of abnormalities in fish are not currently being acquired, even for Biscayne Bay. Establishment of a continuing small scale monitoring program in Biscayne Bay to follow on the Gassman et al. (1995) and Schmale (undated) work will be necessary to compute this index annually. The monitoring would take place twice a year at four locations. Collections would be by means of a chartered bait shrimp boat. Data should also be acquired for development of this index for the St. Lucie-Indian River estuarine system.
The research group at the University of Miami (Gassman et al. 1994, Schmale, 1995, Schmale 1996) are conducting physiological and biochemical studies to look for mechanisms and associates that will improve the scientific understanding of why high prevalences of fish abnormalities occur in Biscayne Bay. Continued work of this type will be extremely useful in interpreting monitoring results and generating community support and cooperation for reducing the inputs of environmental stressors.
A pilot project to relate the spatial distribution of fish abnormality prevalences in the St. Lucie-Indian River System to sediment contaminants would be a useful precursor to a monitoring program and is needed to develop a quantitative baseline on prevalences for this area. A study of deformities in relation to sediment contaminants in the St. Lucie-Indian River area would complement to the Biscayne Bay work still in progress and may reinforce the evidence for a connection between deformities and contaminanted sediments. (Note: The Miami Laboratory of the Southeast Fisheries Science Center, National Marine Fisheries Service, began a pilot study to describe and quantify the externally visable abnormalities in fish of the St. Lucie-Lower Indian River estuarine system in November, 1996. Preliminary examination of the data indicate prevalences of several gross pathological abnormalities are very high, particularly in sea bream.)
Data on other fish abnormalities, including other deformities and disease conditions such as fin rot, tumors, and lesions should be monitored along with the two deformities recommended as the basis of indices. These conditions may also decline in prevalence if the stressors in a system are reduced.
A metric based on sublethal effects could be valuable as a tool in monitoring water quality. Measurable biological responses are needed to adequately assess the quality of estuarine habitat as it relates to contaminants because some chemicals have biological effects in quantities below present detection levels, many chemicals are released into the South Florida environment, and chemicals can act additively or synergistically, compounding effects.
While we have no absolute proof that the deformities recommended as indices are related to sediment contaminants, their higher prevalence at some locations and their presence in several unrelated species of fish suggests an environmental cause (Gassman et al. 1994). The fact that the species primarily affected are bottom species implicates sediments. Bay sediments contain a number of contaminants, and concentrations are higher at some sites (Gassman et al. 1994).
A reduction in the input of contaminants to the Bay would be expected to result in a decline in the prevalence of deformities in fish, which should be particularly noticeable at near the sites receiving discharge waters. There could be a delay in observing beneficial effects because of the storage of contaminants in existing Bay sediments, however it is expected that a layer of sediments with lower associated contaminants would gradually cover previous deposits and reduce their influence on fish if a reduction in contaminant loads in new sediments occurred.
Fish abnormalities also are common in fish of the St. Lucie-Indian River area. Success criteria based on the prevalence of deformities and other abnormalities in fish should be developed for that area.
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