Category: Fish/Shellfish Research
Published: May 1997
Author(s): James E. West
Effective protection and restoration of marine life requires an understanding of the anthropogenic (Literally, "of human origin") stressors and natural limiting factors affecting those organisms. In addition, changes in the abundance or distribution of any species affects others in the ecosystem, including the types of changes in habitat that occur when abundance of plant species increases or decreases. These factors are not always considered in management schemes.
This report was commissioned by the Puget Sound Water Quality Action Team with funds from the U.S. Environmental Protection Agency, and was written to provide the Washington component of the Transboundary Protect Marine Life Work Group with
- identification of species whose populations have experienced significant declines, or are suspected of being significantly stressed in Washingtonâ€™s inland marine waters,
- evaluation of anthropogenic and natural factors contributing to population declines or other stress,
- evaluation and summary of current management approaches to protecting or restoring these species, and
- recommendation of ways to improve awareness of management agencies to status and trends of stressed species, as well as alternate or additional strategies to restore them and protect them from further loss.
Often resource management seeks to optimize harvest of a species or group. This report is more concerned with protecting declining populations of both harvested and non-harvested species, without discussion of ways to optimize harvest yields.
Thirteen species or groups (Resources) are identified as having undergone substantial declines in regional population abundance in recent years; they are in need of attention now to ensure successful protection or recovery. Resources include three invertebrates (Olympia oyster, pinto abalone, and a grouping of species termed "Unclassified Marine Invertebrates"), six fish species or groups of species (Pacific herring, Pacific cod, Pacific hake, walleye pollock, three species of demersal rockfish, and lingcod), three seabirds (marbled murrelet, common murre, and tufted puffin), and one mammal (harbor porpoise). Although the present report discusses the status and management of the thirteen Resources only in Washingtonâ€™s waters, much of the analysis is applicable to British Columbian waters.
The known and surmised effects on these thirteen Resources of four major anthropogenic Stressors -- harvest, habitat loss, pollution, and disturbance -- are summarized and discussed, using best available literature, expert opinion, and common sense. The effects of Natural Limiting Factors (NLF) on these species are treated similarly. Although no attempt is made to identify the relative degree to which Stressors or NLFs have affected Resources, Stressors are grouped, qualitatively, according to whether their effects are considered major or minor. Recommendations for restoration and better protection of Resources are summarized for each Resource and for each Stressor.
Harvest (targeted harvest or bycatch) is considered a major Stressor on all species except Pacific herring and tufted puffin. Recommendations to reduce this Stressor include better, and regular, assessment of the abundance of all organisms (as a prerequisite to understanding the scope of the problem); maintaining or increasing harvest restrictions on all harvested Resources; modifying harvest gear to minimize entanglements of seabirds and harbor porpoise; quantifying better the sources of seabird and porpoise bycatch-mortality; and establishing a system of Marine Protected Areas that would provide refuge from harvest for several species.
Habitat loss and degradation are considered major Stressors for Olympia oysters and Unclassified Marine Invertebrates and minor Stressors for Pacific herring, Pacific cod, walleye pollock, demersal rockfish, and lingcod. Recommendations for reducing the negative effects of habitat loss on stressed species are detailed and extensive, focusing on protecting the function of nearshore vegetated habitats, including reducing anthropogenic turbidity, sedimentation, and eutrophication of intertidal and shallow subtidal habitats. Specific recommendations include establishing a clearly documented and formalized seagrass and seaweed policy (with a number of stipulations designed to protect the function of these habitats in the ecosystem), monitoring vegetated inter- and subtidal habitats along with the effects of anthropogenic turbidity, sedimentation, and eutrophication, encouraging basic research on the ecological function of nearshore habitats, and enhancing education and outreach programs.
Pollution is considered a minor Stressor on all Resources; however, this categorization reflects more a lack of information regarding the health effects of contaminants on marine organisms, than any meaningful comparison. Contaminant levels already detected in Puget Sound organisms are likely to have some negative effects on reproduction, however, basic research is lacking to quantify this for stressed Resources. Potential effects from episodic disasters like oil spills are beyond the scope of this report. Recommendations focus instead on a better understanding of the extent, nature, and health-effects of historic and current contamination and include (1) expanding existing monitoring efforts to evaluate effects of contaminants on the health or reproduction of Resources known or suspected to experience high exposure to contaminants; (2) continuing research on English sole, and reinstating contaminant monitoring of an invertebrate-indicator, as models of contaminant pathways and effects in Puget Sound organisms; (3) evaluating the effects of chronic, low-level sea-surface contamination on the health and reproduction of seabirds and other surface-oriented organisms; and (4) monitoring baseline contaminant conditions in Puget Sound organisms to better evaluate future changes.
Disturbance as a result of human activities or presence is considered a major Stressor for harbor porpoise and nesting tufted puffins. Substantial efforts to reduce this stressor by protecting nesting seabird colonies have already been implemented; recommendations for better protection include designating areas of low vessel traffic to protect surface-dwelling, noise-sensitive species like harbor porpoise and seabirds.
Natural Limiting Factors affect the population abundance of all organisms; recent shifts in environmental conditions (whether anthropogenic or not) are thought to be factors in recent declines in abundance of Pacific cod, walleye pollock, and Pacific hake in Puget Sound. In addition, variability in prey abundance and its effects on growth and survival of nestlings is considered a potential Natural Limiting Factor for all three seabird species. Climate-related variability in predators of Pacific herring is considered a potential cause for regional declines in adult populations of that species. The potential effects of global warming on Puget Soundâ€™s ecosystem are briefly discussed.
The effects of anthropogenic reductions or increases of any species on the overall integrity and function of the marine ecosystem are also considered. Reductions in prey abundance, combined with relative increases in abundance of predators and competitors of Resources, may contribute to the decline of stressed Resources or may prevent their recovery. Examples are provided: fishery enhancement of chinook and coho salmon (by extended-rearing programs) is considered a potential minor Stressor on a number of marine organisms, whether from increased predation by, or competitive interactions with, increased populations of resident salmon. Increased populations of pinnipeds (harbor seals and California sea lions), resulting from their protection by the Marine Mammal Protection Act, are considered a major stressor on Pacific herring, and may be inhibiting recovery of populations of Pacific hake, walleye pollock, Pacific cod, demersal rockfish, and lingcod. Aquaculture of Pacific oysters is considered a major modifier of nearshore marine habitats; however, the extent of the problem and impact on stressed Resources is poorly understood in Puget Sound. Recovery of bald eagle populations is thought to be responsible for abnormally high mortality of nestlings of already-stressed common murres at Tatoosh Island. A significant problem for management is that response of a "healthy" ecosystem to loss or reduction of one species may be an increase in another (or others). In this way, "desirable" species, such as codfishes, may be replaced by "undesirable" species, such as dogfish -- a normal, healthy response of an ecosystem under stress. Resource managers should anticipate changes in community structure and food-web dynamics from the selective removal, enhancement, or protection of any species.
Populations of all species vary substantially as a normal manifestation of the cyclic nature of ecosystem productivity. The species in this report were included in a large part because they are valuable to humans in some way. However, it is clear that all species contribute to the normal function of an ecosystem, regardless of their value to humans. Maintaining ecosystem health relies on our ability to protect the viability of all species to some degree, as well as their habitats. Successful protection and restoration of a healthy ecosystem that can provide sustainable harvests has two important prerequisites: (1) a clear mandate to managers that the ecological connectedness of all species be considered in management schemes, and (2) provision of the resources with which to accomplish this.