An important consideration for proposed developments in New York Harbor is whether the effects of piers can be mitigated through structural modifications. We did not attempt to compare various pier characteristics in our studies, however, others have identified several key features of man-made structures that affect growth of adjacent vegetation and it may be that some of those factors are important for fishes and invertebrates as well. For example, dock height (distance from the water's surface) has been shown to be an important factor affecting growth of vegetation (Kearney, Segal, and Lefor, 1983;Burdick and Short, 1999). It follows that structures that float directly on the water's surface would allow the least amount of light penetration below and may, in fact, be a worst-case scenario for visual feeders. Similarly, pier width could have an affect on light penetration. The piers examined in our studies were extremely wide and covered in asphalt, allowing no light penetration immediately beneath their surfaces. Future pier construction efforts could consider a light-penetrable design. Artificial lightingbeneath piers is probably not as efficient as allowing incident sunlight to pass through because fishes are sensitive to the characteristics of the light spectrum as well as to its absolute light intensity (Fernald, 1993). Finally, piers that are built in a north-south direction tend to support greater densities of eelgrass than piers that run east-west (Burdick and Short, 1998) because an east-west configuration follows the daily path of the sun and results in continuous shading beneath the pier.
It is currently not known whether the effects of piers can be reduced with nominal structural revisions or whether more drastic remedies are required. Studies that more closely examine the effects of edges may provide some answers. Fish abundances are higher at edges than under piers (Duffy-Anderson et al., 2003) and growth can occur at edges even among fish species that show negative growth under piers (Duffy-Anderson and Able, 1999). Pier edges have the potential to modify the intensity of shading by diffusing the pier shadow (Burdick and Short, 1998) and the duration of shading by refracting incident light. Our results suggest that some easing of shade effects occurs around edges so pier designs that allow greater edge-to-surface ratios may be preferable.
Future work should be conducted to determine how broadly applicable our observations of pier impacts are. The studies discussed in this chapter were conducted underneath very large piers but marinas, fishing piers, and individual boat docks allhave the capacity to shade potential fish habitat. Shade-related impacts in these systems may be of even greater concern as many of these smaller piers are often constructed in natural, shallow-water areas that provide important habitat for young-of-the-year fishes (Able and Fahay, 1998; Minello, 1999). The effects of piers in oceanic environments has not been well studied. Oceanic piers exist in many coastal communities but their effects on fishes are still unknown. Examples of ocean-side structures that could have shade-related impacts includebeach-side homes, condominiums andho-tels, and large, public piers. Studies that examine the impacts of piers in these environments are much needed and could provide important information on habitat use, growth, survival, and recruitment.
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