Bluefish, Pomatomus saltatrix are the subject of valuable and popular recreational and commercial fisheries around the world, and populations have shown dramatic fluctuations in abundance. Consistently ranking in the top ten species harvested by weight by recreational marine anglers in the Mid-Atlantic, landings averaged 22,000 metric tons per year from 1974-2001 and commercial landings averaged an additional 14 million lbs per year (Lewis 2002). Substantial declines in catch over the past decade have triggered concerns. Recruitment has been declining since 1989, but the cause of the decline is still unknown (Lewis 2002). Possible causes include overfishing, declining habitat quality and reproductive success, and shifts in feeding ecology (MAFMC 1998).
Estuaries along the Mid-Atlantic Bight are considered “essential fish habitat” for young of the year (YOY) bluefish (Fahay et al. 1999, NOAA 2006). Their health at this life stage is an important factor determining the stock size of fish (Gartland et al. 2006). Their residence in contaminated estuaries during critical periods of growth, their high lipid content, and their piscivory make bluefish likely to acquire high levels of contaminants that biomagnify up the food chain (O’Connor et al. 1982, Kennish and Ruppel 1998, Buckel et al. 1999, Deshpande et al. 2002). We have previously shown in a lab experiment that YOY bluefish from Tuckerton, NJ (a relatively clean estuary) accumulate very high levels of PCBs and chlorinated pesticides when fed prey from the contaminated Hackensack River, NJ. Feeding on the contaminated prey resulted in a significant reduction in appetite, swimming activity, and growth (Candelmo 2005, Candelmo et al in preparation). Thus, fish from contaminated sites like Hackensack would be migrating out of the estuaries slower and smaller, and therefore potentially more vulnerable to predation and starvation (Buckel et al. 1999) than fish that had been in cleaner estuaries.
- We wish to obtain additional information on the PCB and mercury concentrations of YOY bluefish and their prey from the nursery estuary in the Hackensack River, NJ. PCB congeners are accumulated at different concentrations depending on the predator, prey item, and location. Each group will also be analyzed for PCB fingerprinting to see which congeners are preferentially accumulated in the different species and up the food chain (Deshpande et al. 2000, Feldman and Titus 2001). Existing raw data from a study assessing depuration of PCBs in YOY bluefish from Hackensack River will be analyzed to gain an understanding on the longevity of the PCB concentrations and the congener fingerprints these bluefish acquire while residing in these estuaries. Since mercury is another contaminant that can biomagnify up the food chain (as methylmercury) and can cause behavioral changes such as were observed in the experimental bluefish (Weis et al. 2001), prey species, prey in bluefish guts, lab bluefish, and field-collected bluefish from both sites will be analyzed for mercury.
- We will investigate the physiological and biochemical changes from contaminant exposure that may cause changes observed in the YOY behavior and growth. Endocrine disruption, particularly thyroid dysfunction, from contaminant exposure may be an underlying mechanism for the observed behavioral and growth effects (Zhou et al., 1999). Therefore comparison of the thyroid histology and hormone levels in the Tuckerton fish fed Hackensack prey vs Tuckerton fish fed Tuckerton prey will be done. A comparison of the lipid composition of YOY bluefish collected from both sites in the field and the two groups of experimental bluefish will examine any differences in lipid storage when feeding on contaminated prey, which would also have implications for survival in the ocean.
- We will also use this data to gain a better understanding of the foraging ecology of YOY bluefish in the Hackensack River/Newark Bay and how it may affect their contamination levels. A trend has been observed in the prey species (menhaden and mummichogs) that those found in the bluefish guts had higher PCBs than field-caught fish, suggesting that fish with higher body burdens are easier to capture, resulting in transfer of greater amounts of PCBs. Results were not statistically significant, but the number of samples was low. Therefore, additional PCB and mercury analysis on field-caught prey and those in the bluefish guts will be done to see if a larger “n” would demonstrate statistical significance. Bluefish may be preferentially feeding on prey that are slower (Smith and Weis 1997, Weis et al. 2001).
- We will investigate behavioral differences in field-collected bluefish from both sites at the end of the summer to see if the effects seen in lab-exposed fish are also manifested in those collected from the field.
- PCBs of the samples will be extracted with methylene chloride using an automated Soxhlet extraction apparatus. Extracts will be purified with size-exclusion HPLC and analyzed by GC with Electron Capture Detection. Select extracts will be analyzed by GC MS to provide information on the presence of specific PCB congener signatures (Deshpande et al. 2000). Mercury will be analyzed with a mercury analyzer for each group of bluefish, prey items (mummichogs and menhaden), and gut contents, after microwave digestion. These analyses will be done at the NMFS lab in Sandy Hook, the MERI lab, and the lab of Dr. P. Weis at UMDNJ, Newark.
- Thyroid hormones will be assayed in muscle tissue from the bluefish that had eaten Hackensack vs Tuckerton prey. Heads will be removed and preserved and sagittally sectioned near the midline, where, after staining, thyroid follicles will be located and their diameters and cell heights measured. Lipids in both groups of fish will be analyzed by TLC with Flame Ionization Detection using an Iatroscan.
- YOY bluefish will be collected from Hackensack River estuaries and additional gut contents and field collected mummichogs and menhaden will be analyzed for PCB levels.
- Laboratory behavioral experiments will be performed comparing Hackensack and Tuckerton field caught YOY bluefish in the early fall to see if the Hackensack wild fish also have reduced appetite and swimming activity, as seen in those in the experiment.
The Fishery Management Plan for bluefish reported in 2002 that future research needed to include the study of contaminants on their survival, and include studies on predator/prey relationships (Lewis 2002). This project will provide better insight into the foraging ecology and recruitment success of young-of-the-year bluefish residing in polluted habitats such as the Hackensack River. It is important to assess how characteristics of a habitat might affect the quality of the YOY, creating a linkage between habitat quality and year class strength. The study will foster collaborations among Rutgers professor Weis, graduate student Allison Candelmo, the NOAA Fisheries Lab in Sandy Hook, and the MERI lab, and provide data for future proposals to NOAA or other federal agencies.
PCB fingerprints can provide a means to identify which estuary the fish migrated out of after they have joined the adult population, and possibly how much these fish from contaminated estuaries are contributing to the stock. Mid-Atlantic estuaries have varying degrees of contamination, and other commercially and recreationally important fish use them as nursery grounds. It is important to identify effects of contaminants on their health and survival, because changes in behavior and possible decreases in juvenile survival may alter community dynamics as well as cause an overall decline in stocks.
The research will also provide data for the improvement of fish advisories. The human health risk from consuming fish, especially self-caught fish is an important issue. Relationships have been reported between mercury and PCB levels in fish, fish consumption by pregnant women, and deficits in neurobehavioral development in children. In order for fish advisories to be effective it is necessary to have information on contaminant loads in the fish that subsistence and recreational fishermen are catching. Because bluefish are migratory, the location of catch does not denote prior residency and won’t indicate contaminant exposure (Gartland et al. 2006). Overall, a better understanding of the condition of the young-of the year bluefish when they migrate from contaminated estuaries will help implement improved management plans and fishery advisories for this species.
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- Candelmo, A., A. Deshpande, J. Weis. in preparation. Behavior and condition responses of young-of-the- year bluefish (Pomatomus saltatrix) to contaminants via trophic transfer.
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