Southern California Bight 2003 Regional Monitoring Program: IV. Demersal Fishes and Megabenthic Invertebrates



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Summary and Conclusion


  1. Parasite infestation varies according to host species. Some hosts, such as fantail sole, California scorpionfish, and California halibut, appear to be more susceptible to parasites than other hosts, such as California tonguefish and slender sole.

  2. Prevalence varies according to parasite species. The parasitic copepods Lepeophtheirus rotundipes and Naobranchia scorpaenae, found exclusively on California halibut, were conspicuously the most prevalent parasite species collected in the SCB (88.4% and 78.2%, respectively).

  3. California scorpionfish had the highest mean intensity of ectoparasites of any fish species examined to date.

  4. Many ectoparasites are host species and/or host genus specific (26 of 39 species appear to be specific for a single host species or host genus).

  5. Copepods are by far the most abundant group of ectoparasites on fishes living in the SCB (12,795 out of 14,620 individuals).

  6. The following parasite-host combinations are of bioindicator utility in the SCB:

  • caligid copepod chalimus larvae on bigmouth sole

  • the copepod Acanthochondria fraseri on hornyhead turbot

  • gnathiid isopod praniza larvae on hornyhead turbot

  • the copepod Holobomolochus prolixus on speckled sanddab




  1. The total prevalence of ectoparasites on bigmouth sole was significantly highest at Large- and Small-Outfall areas.

  2. The total prevalence of ectoparasites on hornyhead turbot was significantly highest at Small-Outfall areas.

  3. The higher prevalence of ectoparasites on hornyhead turbot and bigmouth sole at the shallow Small-Outfall areas rather than the deeper Large-Outfall areas may be due to higher temperatures at the shallow depths rather than outfall effects.

  4. The host-ectoparasite relationships of California scorpionfish, speckled sanddab, bigmouth sole, and hornyhead turbot are complex and deserve further study.

  5. Three new species of leeches and one new species of parasitic copepod were found in this study.

  6. Fifty-six new host records were reported.

VIII. Bioaccumulation




Introduction


Large quantities of the chlorinated hydrocarbons dichlorodiphenyltrichloroethane (DDT) and polychlorinated biphenyls (PCB) have been historically discharged to the southern California Bight (SCB). An estimated 41.5 metric tons (mt) of DDT and 55.5 mt of PCB have been discharged to the SCB since 1971 (Schiff et al. 2000, Raco-Rands and Steinberger 2001). The DDT emanated from the Montrose Chemical Corporation, formerly the worlds largest manufacturer of chlorinated pesticide, and was discharged through the Los Angeles County sanitary sewer system ocean outfall (Stull 1995). Sources of PCBs included ocean dumping, wastewater discharges, vessel coating, surface runoff and other nonpoint sources (Mearns et al. 1991). Since 1970 when the use of DDT was banned and Montrose halted production, discharges from the ocean outfalls in the SCB have dramatically decreased and DDT emissions are generally nondetectable. Municipal waste discharge of PCBs (as well as other sources) have decreased dramatically as well (Mearns et al. 1991). However, the legacy of this contamination is still observed in the SCB. For example, the highest sediment total DDT concentrations in the SCB are found on the Palos Verdes Shelf on the Los Angeles margin, and it is thought that an estimated 100 mt may still reside in these marine sediments (Lee and Wiberg 2002). DDT and PCB contamination remains widespread, with more than 82% of the ocean floor in the SCB has sediments with measurable DDT and/or PCB (Schiff 2000).
The historical inputs of DDT and PCBs have also resulted in exposure and impacts to biota. As in sediments, contamination of biological organisms has been widespread. Marine bivalves had detectable concentrations of DDT along the entire 350 km coastline of the SCB (Mearns 1993). An estimated 96% of the Pacific sanddab population, the most common flatfish on the shelf, is contaminated with total DDT and/or total PCB (Schiff and Allen 2000) and 99% of the sanddab guild (the most widespread foraging guild on the shelf) had detectable levels of DDT in 1998 (Allen et al. 2002a, 2004b). Reproductive impairment due to DDT and/or PCB was observed in white croaker in the 1980s (Cross and Hose 1988, Hose et al.. 1989). Health-risk advisories to warn anglers still exist along many kilometers of the southern California coastline for several species, including white croaker (OEHHA 2006). Historically, reproductive success was impaired in pinnipeds, such as the California sea lion (Zalophus californianus) that suffered from premature pupping (Delong et al. 1973) or seabirds, such as the brown pelican (Pelecanus occidentalis) that suffered from eggshell thinning (Gress 1994). While these reproductive failures have reversed themselves, other high level predators continue to struggle. For instance, transplanted bald eagles (Haliaeetus leucocephalus) hatched their first two chicks on the California Channel Islands in more than 30 years (D. Witting, NOAA, NMFS, Southwest Regional Office, Long Beach, CA, personal communication May 13, 2006). Concentrations of total DDT and total PCB still average 150 ug/kg in the blubber of marine mammals such as California sea lions in 2000 (LeBouf et al. 2002).
While contaminant pathways to sediment associated biota are well documented, contaminant pathways to higher-level predators are still uncertain. For example, tissue concentrations of flatfish are highest on the Palos Verdes Shelf where sediment concentration maxima are located (Mearns et al. 1991; Allen et al. 2002a, 2004b). Bightwide relationships between sediment contaminant concentrations and flatfish tissue concentrations were highly correlated for both total DDT and total PCB (Schiff and Allen 2000; Allen et al. 2002a,b, 2004b). Moreover, different flatfish species within the same foraging guild and having similar lifestyles accumulated similar quantities of total DDT and total PCB with exposure to the same contaminated sediments (Allen et al. 2002b). In contrast, little data exists in pelagic forage fishes and squid that might serve as pathways to mammals and seabirds. Both northern anchovy and California market squid are primary prey items for the California sea lion in the SCB (Antonelis et al. 1980, Lowry et al. 1991, Lowry and Carreta 1999). Brown pelican was reported to feed consistently on northern anchovy and its breeding status in the SCB has been strongly linked to anchovy abundance and availability (Anderson et al. 1980). Pacific whiteside dolphin (Lagenorhynchus obliquidens) also commonly forages on small pelagic fishes and squid, while the harbor seal (Phoca vitulina), short-beaked common dolphin (Delphinus delphis), and bottlenose dolphin (Tursiops truncatus) forage mainly on other types of fish (Pauly et al. 1998). Additional wildlife predators of pelagic forage species such as northern anchovy, California market squid, Pacific sardine, and Pacific chub mackerel include larger pelagic fishes of the SCB such as Pacific barracuda (Sphyraena argentea), Pacific bonito (Sarda chiliensis), tunas (Thunnus spp.), and yellowtail jack (Seriolis lalandi; Leet et al. 2001).
The primary objective of this study was to assess the extent and magnitude of total DDT and total PCB in pelagic forage fishes and squid within the SCB. This goal will be addressed by answering two basic questions: 1) What percentage of the pelagic forage fish and squid biomass exceeds wildlife risk screening values?; 2) Are there geographic patterns in the concentration of total DDT, total PCB, or the percentage of biomass that exceeds thresholds of concern? These data can then be used for determining potential pathways to higher predators such as marine mammals and birds.

Results


A total of 99 composite samples, representing 1,460 individual fish or squid were collected for organic contaminant analysis (Table VIII-1; Figure VIII-1). Samples of the four target species were collected from each of the four regions identified. Sample sizes ranged from 34 composites for Pacific sardine to 13 composites for Pacific chub mackerel. Bait and landing composites were treated equally throughout the data analysis process. Concentrations of total DDT and total PCB in bait receiver and commercial landing composites for both northern anchovy and Pacific sardine were not significantly different (p >0.05). Despite combining composites from commercial landings and bait receivers, not all of the sampling targets were achieved for each species. For example, only 70% of the target samples were collected for northern anchovy.

Sample Representation


California market squid (34 x 103 mt) and Pacific sardine (14 x 103 mt) comprised over 90% of the total biomass landed in the SCB during this study (Figure VIII-2). These two species were sampled with the greatest success in the survey. Pacific chub mackerel (4 x 103 mt), the species that was sampled with intermediate success, comprised 6% of the total biomass landed during the study period. Northern anchovy (2 x 103 mt), the species sampled with the least success, comprised less than 3% of the total biomass landed during the study. Jack mackerel, which was not sampled, comprised only 1% of the total biomass landed during the study period.
While target sample sizes were not achieved for all species and strata, the sampling effort was representative of the appropriate geographic distributions of pelagic forage fishes and squid that were commercially landed in southern California (Figure VIII-3). For example, 71% of all Pacific sardine were landed in the central stratum and this study representatively sampled 92% of these landings. Similarly, representative samples were collected for the majority of landings of California market squid. A very small proportion of the landings from the islands stratum offset the lack of sampling success in the southern SCB. Representative sampling of the majority of the northern anchovy landings was not achieved as these were dominated by fisheries in the northern SCB. Approximately 50% of the Pacific chub mackerel were representatively sampled.

Total DDT and Total PCB


Tissue concentrations differed among species (Figure VIII-4; Table VIII-2). Northern anchovy had the highest biomass-weighted average concentrations of total DDT (61 +38 SD ug/kg ww). All but one of the northern anchovy samples had detectable quantities of total DDT and these concentrations ranged from 3 to 135 SD ug/kg ww. California market squid had the lowest biomass-weighted average concentration of total DDT (0.8 +1.2 SD ug/kg ww). Fifty percent of California market squid samples had nondetectable concentrations. Pacific sardine and Pacific chub mackerel had intermediate biomass-weighted average concentrations of total DDT (34 +29 SD and 41 +40 SD ug/kg ww, respectively). Both species also ranged in total DDT concentration from 3 to >100 ug/kg ww with only a single nondetectable sample (for Pacific sardine). Pacific chub mackerel had the maximum total DDT concentration of all three species (141 ug/kg ww). The distribution of total PCB concentrations between species followed the pattern of total DDT concentrations, but was lower by approximately one order of magnitude (Figure VIII-4). For example, the biomass-weighted average total PCB concentration in northern anchovy was 3 +5 SD ug/kg ww.
Despite within-strata variability, the central stratum generally had the highest mean concentrations of detectable total DDT and total PCB (Table VIII-2 and VIII-3). Detectable concentrations of total DDT were higher in the central stratum for three of the four species. Interestingly, the islands stratum contained the highest average total DDT concentration for northern anchovy. The highest average total PCB concentrations were also observed from the central stratum for three of the four species. Only the southern stratum had greater detectable total PCB concentrations than the central stratum, and this was in Pacific chub mackerel.

Relationship to Lipid Content


Regardless of species or season, concentrations of total DDT appeared to be a function of lipid content (Figure VIII-5). Lipid content and total DDT concentration were significantly correlated for northern anchovy and Pacific sardine (p <0.05). Lipid content explained 43% and 34% of the variability in total DDT concentrations for Pacific sardine and northern anchovy, respectively. Percent lipid content was highest in Pacific sardine (5.0 % ±0.91 SE), followed by northern anchovy (4.1 % ±0.78 SE) and Pacific chub mackerel (2.9 % ±0.34 SE). California market squid had the lowest percent lipid content (1.1 % ±0.16 SE).

Table VIII-1. Sampling success of southern California pelagic forage species targeted for whole fish composite contaminant analysis between July 2003 and February 2004.





Figure VIII-1. Distribution of contaminant sample composites for a) northern anchovy, b) Pacific sardine, c) California market squid, and d) Pacific chub mackerel sampled from southern California commercial fishing markets and/or bait receivers during July 2003 – February 2004.

Figure VIII-2. Total southern California commercial landings of pelagic forage fish and squid landings (metric tons) during the study period, July 2003 – February 2004 (CDFG data, unpublished). PS=Pacific sardine, PM=Pacific chub mackerel, NA=northern anchovy, MS=California market squid.


Figure VIII-3. Representative samples by species and geographic stratum. Gray bars denote the relative percentage of total landings by species for each stratum. Black bars denote the fraction of total landings with a representative sample.


Figure VIII-4. Box plots of a) total DDT and b) total PCB in pelagic forage fish and squid whole fish composites sampled from southern California commercial fish markets and bait receivers during July 2003 – February 2004. (NA=northern anchovy (n=24); PS=Pacific sardine (n=34); MS=California market squid (n=28); PM=Pacific chub mackerel (n=13)).

Table VIII-2. Summary of total DDT (ug/kg) concentrations in southern California pelagic forage fish and squid composites by region within the southern California Bight.



Table VIII-3. Summary of total PCB (ug/kg) concentrations in southern California pelagic forage fish and squid composites by region within the southern California Bight.




Figure VIII-5. Relationship between lipid content and total DDT concentrations in whole fish composites of pelagic forage fishes and squid sampled from southern California commercial fish markets and/or bait receivers during July 2003 – February 2004. Samples represent only those with detectable levels of total DDT (n=80).

Percent of Biomass Above Wildlife Risk Screening Values


Approximately 99% of all commercial landings of northern anchovy in the SCB exceeded wildlife-risk screening values for total DDT during this study (Figure VIII-6). Approximately 86% of the Pacific sardine and 33% of the Pacific chub mackerel commercial landings also exceeded the total DDT screening values during this study. None of the California market squid landings exceeded the wildlife risk screening value for total DDT. The extent of total PCB exceedence of wildlife risk screening values (as TEQs) was much less. Less than 1% of the commercial landings for Pacific sardine exceeded wildlife-risk screening values for birds during this study. None of the other species exceeded the PCB risk screening values for either birds or mammals.

Total Mass of Contaminants in SCB


Based on the total biomass of commercial landings, an estimated 1.3 kg (+95% CI=0.6 kg) of total DDT was contained within the four pelagic fish species examined during this study. Total PCB contained within the four pelagic fish species was 0.06 kg (+95% CI=0.06 kg). Most of the DDT (71%) resides within the landings for Pacific sardine. Pacific sardine had the second highest average concentrations of total DDT and it was the species with the second highest biomass. In contrast, California market squid contained less than 2% of the total DDT mass found in pelagic forage species tissues. While California market squid had the highest landing biomass, it also had extremely low levels of total DDT. Like the total DDT mass estimates, Pacific sardine had the highest quantity of total PCB of all species examined (83%).



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