Use of tissue and sediment‐based threshold concentrations of polychlorinated biphenyls (PCBs) to protect juvenile salmonids listed under the US Endangered Species Act

• 1. Under the Endangered Species Act, the National Marine Fisheries Service has authority to protect listed species from any adverse actions that may jeopardize the population's ability to recover and increase to sustainable levels. Listed salmon species in the northwest United States are known to travel through urban areas in their migration from river to ocean. Species such as the chinook salmon (Oncorhynchus tshawytscha) often spend several weeks in these urban estuaries where they can be highly exposed to urban‐related contaminants that reside in the sediments and accumulate in their prey species. The concern is that these contaminants are bioaccumulated to levels that may impact the ability of individual salmon to grow and mature normally. This paper provides a framework for determining the tissue and sediment concentrations of polychlorinated biphenyls (PCBs) that are likely protective against adverse effects in listed salmonid species.
• 2. The relevant ecotoxicological literature was examined and 15 studies were selected that met the pre‐established criteria outlined here. For each study, the lowest tissue concentration (residue) of total PCBs associated with a biological response was selected. The tissue concentration associated with the 10th percentile of these 15 studies was chosen to represent the residue effect threshold (RET) above which wild juvenile salmonids would be expected to exhibit adverse sublethal effects from accumulated PCBs. This value (2.4 μg PCBs g^?1 lipid) is expressed in terms of the lipid‐normalized concentration because of the large effect lipid can have on the expressed toxicity and the substantial variability in lipid content observed in salmonids over their life cycle.
• 3. A sediment concentration that is expected to produce the RET was then determined using the biota‐sediment accumulation factor approach. The sediment effect threshold, which varies with the total organic carbon content in sediment, is the level above which adverse effects may be expected in juvenile salmonids due to accumulation of PCBs from environmental exposure. Bioaccumulation of PCBs was examined in one river system as a model for determining an appropriate bioaccumulation factor for wild juvenile chinook salmon.
• 4. Evaluation of exposure to potentially deleterious concentrations of PCBs based on tissue residues is the preferred approach; however, the sediment effect threshold may also be used in cases where bioaccumulation has been characterized in an estuary. The threshold values presented here are intended as interim guidelines that should be modified as more data become available. Additionally, because of the uncertainty around many of the factors and assumptions that comprise the single threshold effect values, it is recommended that future studies be employed to help determine a range of acceptable values that would afford protection under various environmental and biological conditions.

Published in 2002 by John Wiley & Sons, Ltd.     

Assessing the role of the aquatic Natura 2000 network to protect both freshwater European species of community interest and threatened species in a Mediterranean region

1. The European Natura 2000 (N2K) network of protected areas stands out as the main conservation strategy in the European Union to preserve biodiversity under the auspices of the Convention on Biological Diversity.
2. The management of N2K sites is mainly focused on protecting the biological elements as Special Areas of Conservation for habitats or species listed in the European Habitats Directive, or as Special Protection Areas for birds listed in the European Birds Directive for which the site was designated. It seems urgent, therefore, to discriminate which N2K sites are really providing effective protection for aquatic biodiversity.
3. Although the main objective of N2K is to protect species listed in the Birds and Habitats Directives, the conservation status of threatened species included in the European Red List of the IUCN must also be a concern for the European Union.
4. Focusing on Central Spain as a case study, the aim of this work was to evaluate how far aquatic N2K (i.e. N2K sites designated for the occurrence of freshwater elements) is effective in protecting both those aquatic species in the Directives [referred to here as Species of Community Importance (SCI) and threatened species (TS)].
5. Most of the N2K sites in the study area have been designated using aquatic elements, which means that N2K could theoretically provide appropriate mechanisms to preserve aquatic biodiversity. However, N2K provides a low percentage of overlap with some of the hotspots identified for both TS and SCI. Surprisingly, TS are in general similarly or even better represented than SCI by N2K.
6. N2K may provide good coverage for aquatic biodiversity, mainly by acting as an umbrella for other species, but it could be improved by addressing some spatial gaps, thereby making it more relevant to current challenges such as climate change and other human impacts.