SHOREZONE LITERATURE REVIEW - EFFECTS OF RECREATIONAL AND CONSTRUCTION ACTIVITY|
Effects of Recreational and Construction Activity
The activities necessary for construction of shorezone structures can have direct impacts on ESA-listed salmonids. As enumerated above, the primary impacts of construction activities considered by NMFS, aside from the actual crushing of individual fish, are turbidity produced during pile driving and bulkhead construction/removal, and the effects of shock waves produced by pile driving. Numerous studies have documented the detrimental affects of chronic exposure of salmonids to turbid water in riverine environments (e.g., Sigler et al. 1984). Physiological effects are only apparent after prolonged exposure (3-5 days in the case of Sigler et al. 1984), and chinook and coho juveniles will emigrate from turbid water (Scrivener 1994; Murray and Rosenau 1989; Skeesick 1970; Sigler et al. 1984). However, even low turbidity levels can produce a variety of sublethal effects (i.e., reduced survival, reduced growth, reduced food conversion, reduced feeding, altered diet, stress, disease, avoidance, displacement, altered behavior [including predator avoidance behavior]) that could ultimately reduce the fitness of the individual (reviewed in Lloyd 1987). Further, even minor increases in turbidity in a clear lake can result in significant reductions in primary productivity both through reduction in light penetration and physical coverage of the benthos (Lloyd 1987). Contractors conforming to BMPs specified by WDFW utilize floating "sedimentation control curtains" to contain turbid water, allowing turbidity to settle before removing the curtain. Turbidity from an individual construction activity would not represent a permanent sediment source and would not produce conditions of chronic exposure, but it could be acute. The possibility also exists that fish could be trapped within the sedimentation control curtain, and thus exposed to potentially lethal turbidity levels. Nevertheless, to minimize potential impacts, the Services restrict construction activity to periods when ESA-listed salmonids are least likely to inhabit the area of construction. In the case of NMFS, "allowable construction windows" for the protection of chinook have not been established.
Pile Driving: The expected effects of pile driving on juvenile salmonids can be generally summarized as disruptions of normal behavior. The shock waves generated by pile driving could potentially disrupt the foraging behavior of juvenile salmonids, cause them to move away from the shoreline or exhibit a startle response, or delay migratory progress. Only one published study (Feist et al. 1996) of the effects of pile driving on juvenile salmonids was located. Feist et al. (1996) studied the effects of vibratory and drop hammer pile driving on the behavior of juvenile chum and pink salmon in Puget Sound at the Everett Homeport. They determined that salmonids were capable of detecting the sound of drop-hammer pile driving at least 600 meters away, and that the sound was at least 20 dB above ambient levels at 593 meters. Data collected from the vibratory hammer location was insufficient to allow appropriate analysis; thus, only data analysis from the drop-hammer location was reported. Juvenile pink and chum salmon did not change their distance from shore or cease foraging in response to pile driving, but there were significant differences in the distributions and sizes of fish schools, and behavior within schools on pile driving days versus non-pile-driving days. On pile driving days, there were nearly half the number of fish schools on the construction side of the site than on non-pile-driving days. One concern with pile driving is that the sound will "mask" the sound of an approaching predator, or that salmon would become habituated to the sound and fail to hear the approach of a predator. Qualitative observations indicated that fish had habituated to the sound of pile driving (Feist et al. 1996).
Caveats about the study by Feist et al. (1996) are that this was a study of pink and chum juveniles in a marine environment, not chinook juveniles in freshwater. Second, the study did not investigate the impacts of pile driving on adult salmon behavior. Third, the study investigates one site during one season, and relies predominantly on human observation in the assessment of fish behavior. The extrapolation of these results to other locations, particularly freshwater systems with different species and age classes, may not be valid. Despite these caveats, the implications are that salmonids do respond to pile driving, and until pile-driving effects on freshwater systems are investigated, regulators should assume the potential for adverse affects on ESA-listed salmonids in lakes. Recreational Activities
The effects of recreational activities on ESA-listed salmonids are unknown. Direct effects of boating or swimming on salmonids are expected to be disruptions of salmonid behavior or physical injury due to contact with the boat or entrainment in the propulsion system. Migrating adult chinook in the ship canal have been tracked at depths as shallow as 1 meter (Warner, pers. comm., 7 July 2000), exposing them to potential boat contact. Beak Consultants Incorporated (1998) cited Weitkamp (1982) as indicating "that juvenile salmonids in marine environments near piers returned to their normal behavior immediately after a boat passed." The implications of this statement are that juvenile salmonid behavior was temporarily disrupted by boats. However, we were unable to obtain a copy of the Weitkamp (1982) document, and thus cannot verify this implication or describe the conditions under which the potential disturbance occurred. Mosich and Arthington (1998) reviewed the impacts of power boating and water skiing on lakes and reservoirs, and identified direct boat contact and propeller action as sources of injury to aquatic organisms. In the only direct reference to salmonids, Sutherland and Ogle (1975) cited in Mosich and Arthington (1998) describe significant mortality of chinook eggs resulting from pressure fluctuations created by passing jet boats in shallow water.
Indirect effects of boating on salmonids involve adverse impacts to habitat quality. Substantiated impacts that were discussed at a workshop held at Woods Hole Oceanographic Institute in 1994 include: sediment and contaminant resuspension and resultant turbidity, laceration of aquatic vegetation with loss of faunal habitat and substrate stability, toxic effects of chemical emissions of boat engines, increased turbulence, shearing of plankton, shorebird disturbance, and the biological effects of chemically treated wood used in dock and bulkhead construction (Crawford et al. 1998). The complete proceedings of the workshop (a book) was unavailable, but the abstract was obtained.
The abstract indicated that, while the above potential impacts had been identified, impacts remain "inadequately defined and described," and that sufficient evidence exists to infer that recreational boating is not an environmentally benign activity (Crawford et al. 1998). Mosich and Arthington (1998) in their review of literature on lakes presented a list of impacts similar to that of Crawford et al. (1998), but also added chemical impacts from hydrocarbons, erosion of banks and destruction of emergent vegetation, introduction of plant fragments and plankton via jet-propulsion systems and boat propellers and trailers, and the biological impacts of sediment resuspension and erosion (i.e., clogging of respiratory structures of fish and invertebrates, reduced photosynthesis, increased nutrient
availability). Crawford et al. (1998) expressed concern that the potential for impacts in temperate climates was exacerbated by the "unfortunate synchronybetween the peak season of boating and the occurrence of planktonic embryonic and larval stages of vertebrates and invertebrates in estuaries and coastal waters." This same concern has application to freshwater environments to some degree.Bonham (1983) described the effects of boats and their wakes on river and canal shorelines with specific attention to the effects on emergent and submergent vegetation. Boat wakes erode shorelines and wash soil from the roots of emergent vegetation; emergent vegetation is subsequently uprooted by the wakes (Bonham 1983). Loflin (1995) reported scarring of seagrass flats from boat propellers. Asplund and Cook (1999) discussed the advantages and limitations of "no-wake zones" for protecting fragile lakeshore environments. Unfortunately, only the abstract of this document was obtained, so further comment on Asplund and Cook's (1999) discussion is not possible. Mosich and Arthington (1998) indicated that boat traffic close to shore had the greatest erosive affect. Collins et al. (1995b) found that feeding by small fish in Lake Rosseau, Ontario was suppressed by disturbance from boat wakes.Literature on the impacts of recreational swimming on salmonids was not obtained. As mentioned above, the expected impact is a disruption of salmonid behavior. The rapid movements and splashing of a recreational swimmer would be expected to disturb the foraging behavior of salmonids to some degree. Recreational water use, including boating and swimming (people and pets), could occur independent of the construction and maintenance of docks and bulkheads at private residences. There is recognition that the construction and maintenance of those structures facilitates some recreational activities, and thus some recreational activities are an interrelated or indirect affect of the structures.