PCBs as Novel Tracers for Determining Bluefin Tuna (Thunnus thynnus) Population Mixing in the North Atlantic
PI: Rebecca M. Dickhut (VIMS), Ashok D. Deshpande (co-PI), NOAA-NMFS, NEFSC
PROJECT DESCRIPTION:
The primary objective of this research is to measure PCB (specifically PCB153 and other nonmetabolizable congeners) and chlordane
(cis-chlordane, trans-chlordane, trans-nonachlor) concentrations in bluefin tuna and selected prey fish from the Mediterranean,
western N. Atlantic, and Gulf of Mexico food webs in order to establish the utility of using PCB and organochlorine (OC)
pesticides as tracers of bluefin tuna origin and the extent of stock mixing in the N. Atlantic.
PROGRESS thru 10/31/2006:
Tissue samples (muscle and liver) from 42 bluefin tuna captured off the Virginia coast were collected during July 2006. In addition,
tissue samples from 75 bluefish (Pomatomus saltatrix) from the western N. Atlantic have been collected. To date, ~25% of the
bluefin tuna tissue samples have been extracted and analyzed for PCBs and OC pesticides. It is anticipated that these fish
(93-151 cm curved fork length) represent a mixed population of bluefin tuna from Gulf of Mexico, Mediterranean, and perhaps
other natal grounds. The levels and ratios of PCBs and selected OC pesticides in this suspected mixed population of bluefin
tuna will be compared to those of resident bluefin tuna and selected prey from the Gulf of Mexico, Mediterranean, and western
N. Atlantic (e.g. bluefish) to establish the utility of using PCB and organochlorine (OC) pesticides as tracers of bluefin tuna
origin and the extent of stock mixing in the N. Atlantic.
PRELIMINARY DATA:
The data collected thus far demonstrate that western N. Atlantic bluefin (this study) have significantly lower levels of PCBs and
organochlorine pesticides compared to resident bluefin tuna from the Mediterranean (Kannan et al., 2002). This suggests that
the marine food web of western N. Atlantic has a much lower level of contamination than the Mediterranean food web. However,
bluefin tuna captured in the western N. Atlantic may still include fish from the Mediterranean that migrated to the region
prior to acquiring high body burdens of PCBs and OC pesticides. Levels of PCBs and OC pesticides increase linearly in bluefin
tuna (27 – 186 cm) by <1x to >10x per cm of body length (Uneo et al., 2002). Therefore, multiple markers will be
used in this study as tracers of bluefin tuna origin and the extent of stock mixing in the N. Atlantic.
Kannan, K., et al. Ambio 31:207-211, 2002.
Uneo, D., et al., Mar. Pollut. Bull. 45:254-261, 2002.
Figure 1: Persistent organic pollutant levels in bluefin tuna (Thunnus thynnus) from the
western N. Atlantic (Dickhut et al.,
unpublished) and the Mediterranean (Kannan, K., et al. Ambio 31:207-211, 2002).
Fish size (curved fork length) given in
parentheses.
Do not reproduce or reference without the permission of R. Dickhut
Plans for the next six months to year: (one paragraph)
We plan to obtain additional bluefin tuna and/or prey samples from the Gulf of Mexico, Gulf of Maine, and Mediterranean. These
samples will then be analyzed for PCBs and OC pesticides. The Gulf of Mexico and Mediterranean samples will be used to establish
the baseline signals for bluefin tuna from these regions. The Virginia coast and Gulf of Maine samples will be considered
potentially mixed populations; PCB and OC pesticide signals in bluefin tuna from these populations will be analyzed in comparison
to the baseline signals from the Gulf of Mexico and Mediterranean to evaluate the extent of stock mixing.
PUBLICATIONS:
CONFERENCES:
Poster presentation at the North American meeting of the Society
of Environmental Toxicology and Chemistry, Nov. 5-10, 2006 in
Montreal, Canada entitled Persistent Organic Pollutants in
Atlantic Bluefin Tuna
