Commentary of Strategies for Enhancing Marine (and Human) Habitat at Brooklyn Bridge Park

In response to the article on enhancing habitat at Brooklyn Bridge Park, we would like to provide an update and a comment in our continuing evaluation of fish response to alterations of the New York Harbor shoreline. Beyond those papers of ours cited in this manuscript, we have continued to study (2007–present, including at Brooklyn Bridge Park) the fishes, but with a new technique, Dual Frequency Identification Sonar (DIDSON) mounted on a mobile platform (kayak) (Able et al. in review). This approach allows us to evaluate the response of fishes to overwater structures at a variety of spatial scales. These studies indicate that under-pier areas of large piers are also avoided by most water-column fishes (Grothues and Able in prep.). As always, with a group as diverse as fishes there are different, species-specific responses to pier shading. One example is that, unlike many small prey species [i.e. Atlantic silver-sides (Menidia menidia), bay anchovy (Anchoa mitchilli)], large predators such as striped bass (Morone saxatilis) can be found under piers near the edge of the pier in intermediate shade. As a result, it appears that the impacts of shading are more related to the area of the over-water structure relative to the amount of edge, as suggested by others of our ongoing studies. Narrow walk-ways, as planned, may not be a major detriment to fish use. In fact, they could have a positive effect because they provide habitat for large predators and shelter for structure-seeking fishes that live in the water column. The fish response may vary with the type of walkway. Floating walkways provide more shade because they rest on the water’s surface, while pile-supported walkways, which are above the water surface, have less shade. These possibilities need to be evaluated.

Despite these kinds of exceptions, shading is still believed to be a major negative influence on fish use of New York Harbor habitat and other urbanized waters, and any attempts to reduce shading of large areas should have a positive effect on the fishes. Reduced shading in shallow water, as occurred as the result of removal of pier decking and the planned removal of other decking for the boating channel, likely increases the available habitat for fishes. This may be especially important for fishes that migrate along shorelines either upstream (for spawning) or downstream (summer users of upstream areas as they move offshore for the winter). This interpretation is supported by others studying fish in urban habitats in the Pacific Northwest (Nightingale and Simenstad 2001).

As always, these suggestions need to be rigorously evaluated, in order to guide future restorations of urbanized shorelines.