Sharks, turtles, billfish, and marine mammals are frequently caught accidentally in commercial fisheries. Although conservationists and fisheries managers encourage the release of these nontarget species, the long-term outcome of released animals is uncertain. Using blue sharks Prionace glauca, we developed a model to predict the long-term survival of released animals based on analysis of small blood samples. About 5% of the sharks were landed in obviously poor condition (lethargic and unresponsive to handling); these moribund sharks were sampled and euthanized. A subset of the remaining sharks was sampled and tagged with pop-up satellite archival tags (PSATs). Each of the PSATs that reported data (11 tags) showed that the sharks roamed at sea for at least 3 weeks postrelease. Five variables differentiated moribund sharks from survivors: plasma Mg 2þ (moribund, 1.57 6 0.08 mM; survivor, 0.98 6 0.05 mM; P , 0.00001), plasma lactate (moribund, 27.7 6 4.1 mM; survivor, 5.80 6 2.96 mM; P , 0.001), erythrocyte heat shock protein 70 (Hsp70) mRNA (relative levels: moribund, 3.96 6 0.53; survivor, 1.00 6 0.29; P , 0.005), plasma Ca 2þ (moribund, 3.70 6 0.14 mM; survivor, 3.13 6 0.11; P , 0.005), and plasma K þ (moribund, 7.01 6 0.66 mM; survivor, 5.12 6 0.44 mM; P , 0.05). These analyses were used to develop logistic regression models that could ''predict'' the long-term survival of captured sharks, including a larger group of sharks that we sampled but did not tag. The best logistic model, which incorporated Mg 2þ and lactate, successfully categorized 95% of fish of known outcome (19 of 20). These analyses suggest that sharks landed in an apparently healthy condition are likely to survive long term if released (95% survival based on biochemical analyses; 100% based on PSATs).

Abstract-The removal of persistent chlorinated organic compounds from pulp mill effluents has not eliminated mixed function oxygenase (MFO) induction by these effluents. Therefore, continuous MFO induction downstream of pulp mills may be due to exposure to more labile compounds, such as retene (an alkyl-substituted phenanthrene), which typically cause transient induction after a single brief exposure. Because fish are exposed continuously to pulp mill effluents, we have tested, and rejected, the null hypothesis that continuous exposure of fish to retene does not cause sustained MFO induction. Rainbow trout exposed continuously to retene, a component of some pulp mill effluents and sediments downstream of pulp mills, showed concentration-dependent increases in hepatic ethoxyresorufin-O-deethylase (EROD) activity. The increase in EROD activity was sustained over 32 d of continuous exposure, but it diminished to background levels within 4 d after transfer to clean water. The enzymatic response was confirmed by measuring changes in the content of immunodetectable cytochrome P4501A (CYP1A) protein. These data support a role for labile, nonhalogenated compounds in chronic effects of pulp mill effluents on fish.

SUMMARY We investigated if seasonal changes in rainbow trout muscle energetics arise in response to seasonal changes in erythrocyte properties. We assessed if skeletal muscle mitochondrial enzymes changed (1) acutely in response to changes in erythrocyte abundance, or (2) seasonally when we altered the age profile of erythrocytes. Rainbow trout were treated with pheynylhydrazine,causing a 75% reduction in hematocrit within 4 days. After erythropoiesis had returned hematocrit to normal, treated and control fish were subjected to a seasonal cold acclimation regime to assess the impact of erythrocyte age on skeletal muscle remodeling. Anemia (i.e. phenylhydrazine treatment) did not alter the specific activities (U g-1 tissue) of mitochondrial enzymes in white or red muscle. Anemic pretreatment did not alter the normal pattern of cold-induced mitochondrial proliferation in skeletal muscle,suggesting erythrocyte age was not an important influence on seasonal remodeling of muscle. Anemia and cold acclimation both induced a 25–30%increase in relative ventricular mass. The increase in relative ventricular mass with phenylhydrazine treatment was accompanied by a 35% increase in DNA content (mg DNA per ventricle), suggesting an increase in number of cells. In contrast, the increase in ventricular mass with cold temperature acclimation occurred without a change in DNA content (mg DNA per ventricle), suggesting an increase in cell size. Despite the major increases in relative ventricular mass, neither anemia nor seasonal acclimation had a major influence on the specific activities of a suite of mitochondrial enzymes in heart. Collectively, these studies argue against a role for erythrocyte dynamics in seasonal adaptive remodeling of skeletal muscle energetics.

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This study investigated whether ethoxyresorufin-O-deethylase (EROD) activity in rainbow trout exposed to mixtures of polycyclic aromatic hydrocarbons (PAHs) could be predicted from induction equivalency factors (IEF). The test PAHs were classified into strong and weak inducers on the basis of similar exposure-response curves. Induction equivalency factors of strong inducers, based on benzo[k]fluoranthene (BkF) as the reference compound, ranged from 0.03 to 0.16. Trout exposed to mixtures of strong inducers (2, 4, and 6 equipotent parts) at 0.32-, 1.0-, or 3.2-nM BkF-equivalents showed exposure-dependent increases in EROD activity, consistent with an additive interaction. The extent of activity did not vary greatly among mixtures and single PAHs at a given induction equivalent quantity (IEQ). Induction equivalency factors could not be calculated for weak inducers because the range of induction was too low. Hence, each weak inducer was added to mixtures at concentrations that induced EROD activity fivefold. These mixtures appeared additive because binary and quaternary mixtures caused about 10- and 20-fold induction, respectively. Strong inducers mixed the same way also showed additivity. In contrast, EROD induction by mixtures containing both strong and weak PAHs was 800 to 900% greater than expected, suggesting synergistic interactions. Therefore, if mixtures are composed of PAHs that behave similarly, IEFs may be a suitable approach for assessing risk. However, for mixtures that contain PAHs of differing potency and efficacy, bioassays will be a more reliable measure of risk than IEFs.

Campana et al. (2009; Mar Ecol Prog Ser 387:241-253) explored the survival of blue sharks Prionace glauca captured and released from the North Atlantic commercial longline fishery. We think that their comments and comparisons do not accurately reflect a previous survival study of blue sharks in Hawaii (Moyes et al. 2006; Trans Am Fish Soc 135:1389-1397). The differences in mortality between the studies, ~5% in the Hawaii-based fishery and ~35% in the North Atlantic fishery, were suggested to be due to failure of Moyes et al. (2006) to accurately reflect commercial fishing conditions. Careful examination of the data, however, suggests that the mortality depends on fisheryspecific features -hook type, soak time and handling of the bycatch during release -rather than the respective tagging protocols. Survival studies based on pop-up satellite archival tags (PSATs) are cost-prohibitive; alternative (e.g. biochemical) approaches to estimate stress and morbidity are needed to supplant PSAT studies and to increase sample sizes. Standardization of fishing methods and sampling protocol is needed for future survival studies, to reduce experimental bias and improve the cost:benefit relationship.

Retene (7-isopropyl-1-methylphenanthrene) is a naturally formed polycyclic aromatic hydrocarbon (PAH) that causes teratogenicity in fish larvae and induction of cytochrome P450 (CYP1A) enzymes. Retene occurs at high concentrations (< or =3,300 microg/g dry wt) in surface sediments contaminated by resin acids from pulp mill effluents. To assess the environmental risks of retene, it is important to evaluate conditions affecting its bioavailability and accumulation by fish. Fingerling rainbow trout were exposed to retene-spiked or naturally contaminated sediments and sampled after 4 d to determine liver CYP1A activity and concentrations of retene metabolites in bile as indicators of retene accumulation. Industrially contaminated sediments collected near a bleached kraft pulp and paper mill discharging to Lake Saimaa, Finland, significantly induced trout liver CYP1A activity, indicating accumulation of arylhydrocarbon receptor (AhR)-active ligands. Bile of these fish contained retene metabolites, providing direct evidence that retene is bioavailable, presumably via desorption from sediments. Induction of CYP1A in fish exposed to sediments spiked with retene or benzo[k]fluoranthene supported this conclusion. While the extent of CYP1A induction by spiked sediments declined after storage (i.e., aging), a portion of the spiked PAHs remained bioavailable. However, retene was not the sole CYP1A inducer in industrially contaminated sediments, as shown by induction in fish injected with sediment extracts oxidized to remove labile PAHs but not persistent organochlorine compounds such as chlorinated dioxins and furans.

The ecological risks of polynuclear aromatic hydrocarbons (PAH) in aquatic sediments will vary with both toxicity and bioavailability to aquatic biota. While there are standardized protocols to test the acute toxicity of sediment-borne compounds to aquatic invertebrates, there are none for assessing bioavailability to fish. We found that sediment-borne PAH caused an exposure-dependent induction of cytochrome P450 (CYP1A) enzymes in rainbow trout (Oncorhynchus mykiss) fingerlings exposed in semi-static 96 h bioassays, as shown by increased activity of ethoxyresorufin-o-deethylase (EROD). Assuming that PAH are taken up by trout due to partitioning from organic and inorganic constituents of sediments, we tested the effect of different test variables on bioaccumulation using induction as an index of exposure. EROD activity increased with exposure of fish to increasing volumes of sediments containing PAH, i.e., with increasing ratios of sediment to water. Uptake of single compounds from sandy sediments did not differ from uptake from clay or low organic (7% LOI - loss on ignition) sediments, but decreased when organic content was very high (58% LOI). Maximum induction was observed within 24 h of exposure and at 7.5 degrees C relative to 15, 22, or 28 degrees C. Storage and handling techniques had minor effects on sediment EROD induction potency. Absolute EROD activity was greater in white sucker (Catostomus commersoni) a benthic species, than in trout, a pelagic species. However, when basal (negative control) activity was accounted for, there was no difference in response between the species. Together, these experiments provide a basis for developing a standard protocol to test the bioavailability to fish of sediment-borne PAH.