Peter J. Auster

The impacts of mobile fishing gear on seafloor habitats in the gulf of Maine (Northwest Atlantic): Implications for conservation of fish populations

Abstract Fishing gear alters seafloor habitats, but the extent of these alterations, and their effects, have not been quantified extensively in the northwest Atlantic. Understanding the extent of these impacts, and their effects on populations of living marine resources, is needed to properly manage current and future levels of fishing effort and fishing power. For example, the entire U.S. side of the Gulf of Maine was impacted annually by mobile fishing gear between 1984 and 1990, based on calculations of area swept by trawl and dredge gear. Georges Bank was imparted three to nearly four times annually during the same period. Studies at three sites in the Gulf of Maine (off Swans Island, Jeffreys Bank, and Stellwagen Bank) showed that mobile fishing gear altered the physical structure (=complexity) of benthic habitats. Complexity was reduced by direct removal of biogenic (e.g., sponges, hydrozoans, bryozoans, amphipod tubes, holothurians, shell aggregates) and‐ sedimentary (e.g., sand waves, depressions)...

Evaluating the role of fish behavior in surveys conducted with underwater vehicles

It is often assumed that visual survey data provide more accurate fish counts than conventional extractive gear. As a result, use of underwater vehicles to assess the abundance and distribution of fishes has increased rapidly over recent years. However, a review of observations reported for 48 demersal marine fish taxa showed that almost all respond in some way to underwater vehicles. Whether or not movements or changes in behavior affect survey bias is more difficult to assess. A simple conceptual model is presented to evaluate relationships between stimulus intensity, distances from the vehicle where reactions occur, and survey bias. Largest bias is caused by attraction or avoidance that occurs outside the field of cameras or observers. While light level and vehicle speed have been explored experimentally in a few cases, much remains to be learned about how bias varies among species, age groups, different vehicles, and operating conditions. Given poor understanding of survey bias, we recommend that surv...

Are deep-water corals important habitats for fishes?

High densities of fishes in aggregations of deep-water corals (e.g., of the genera Primnoa, Paragorgia, Paramuricea) do not necessarily indicate that corals are important habitats in terms of population processes. Frequency dependent distribution models provide a basis for assessing the role of deep-water corals. It is necessary to understand the overall habitat-related distributions of fish species, at particular life history stages, in order to assess the particular role of corals. Examining the landscape for ecologically equivalent habitats is one approach for assessing the importance of coral habitats. Measures of the functional equivalence of habitats are demonstrated, as an example, for sites from the Gulf of Maine on the northeast United States continental shelf. Fish census data based on surveys with a remotely operated vehicle in 2003 showed that communities in habitats dominated by dense corals and dense epifauna were functionally equivalent when compared with five other less complex habitats (e.g., boulder with sparse coral cover). Comparison of species-individual curves showed that sites with dense coral and dense epifauna habitats supported only moderate levels of fish diversity when compared with other sites. Further, density of Acadian redfish (Sebastes fasciatus) in dense coral and dense epifauna habitats, where this species was dominant, was not statistically different but was higher than an outcrop-boulder habitat with sparse epifauna (the only other site where this species was abundant). Such data suggest that coral habitats are not necessarily unique but have attributes similar to other important habitats. However, the level of their importance in the demography of fish populations and communities remains to be demonstrated. Focusing conservation efforts for deep-water corals on their perceived value to exploited species, without good demographic information on fish populations, may ultimately leave corals open to destructive fishing practices if new and contrary information emerges. Conservation efforts for corals, in the absence of explicit ties to managed fish species, might do better emphasizing the intrinsic value of corals, their slow growth, high sensitivity to disturbance, and the questionable potential for recovery.

Distributional responses to small-scale habitat variability by early juvenile silver hake, Merluccius bilinearis

Early juvenile (0-year) silver hake, Merluccius bilinearis, occurred at higher densities on bottoms with greater amphipod tube cover at a 55 m deep site in the Middle Atlantic Bight. The size range of individuals at this site was 1.5–5 cm total length. Additional observations at other sites showed that 0-year silver hake only occurred on silt-sand bottom with amphipod tubes at bottom water temperatures of 8.7–11.4 °C. This distribution pattern could be the result of either selective settlement into appropriate habitats or differential predation with higher survivorship in more complex habitats. We posit that 0-year silver hake occur in patches of dense amphipod tube cover to avoid visual predators and co-occur with preferred prey (i.e., amphipods and shrimps).

Integrating the invisible fabric of nature into fisheries management

Overfishing and environmental change have triggered many severe and unexpected consequences. As existing communities have collapsed, new ones have become established, fundamentally transforming ecosystems to those that are often less productive for fisheries, more prone to cycles of booms and busts, and thus less manageable. We contend that the failure of fisheries science and management to anticipate these transformations results from a lack of appreciation for the nature, strength, complexity, and outcome of species interactions. Ecologists have come to understand that networks of interacting species exhibit nonlinear dynamics and feedback loops that can produce sudden and unexpected shifts. We argue that fisheries science and management must follow this lead by developing a sharper focus on species interactions and how disrupting these interactions can push ecosystems in which fisheries are embedded past their tipping points.

A spatial and temporal perspective on research and management of groundfish in the northwest Atlantic

Abstract Fish populations have been exploited along the northeastern coast of North America for over 500 years. During this period, an extensive knowledge of fish distributions and habitat has developed both as anecdotal and scientific literature. Despite this knowledge, catches and stocks have fluctuated widely. As a result of a large decline in the fish stocks that is primarily attributed to overfishing, the region is currently experiencing the implementation of extreme management initiatives to allow the exploited stocks to recover. As our scientific knowledge of fish populations increases, the question arises as to how we integrate our knowledge of fish and fishers, at multiple scales, and produce a management structure that maintains stocks at sustainable levels. This article addresses that question by reviewing patterns and processes exhibited by both fishers and fish through a hierarchy of temporal and spatial scales. Large‐scale population surveys, for example, document the persistence of patterns...

Anthropogenic Impacts on the Corner Rise Seamounts, North-West Atlantic Ocean

Here we report the first direct underwater observations of extensive human-caused impacts on two remote seamounts in the Corner Rise complex (north-western Atlantic). This note documents evidence of anthropogenic damage on the summits of Kukenthal peak (on Corner Seamount) and Yakutat Seamount, likely resulting from a limited Russian fishery from the mid-1970s to the mid-1990s, highlighting how bottom trawling can have long-term detrimental effects on deep-water benthic fauna.

MARINE PROTECTED AREAS FOR THE TEMPERATE AND BOREAL NORTHWEST ATLANTIC: THE POTENTIAL FOR SUSTAINABLE FISHERIES AND CONSERVATION OF BIODIVERSITY

Abstract Year-round no-take marine protected areas (MPAs) can enhance conservation of exploited species and biodiversity overall. MPAs have the potential to sustain living marine resources and their support systems at genetic, population-community, ecosystem, and landscape levels. From a fisheries perspective they can protect spawning and nursery areas of key species, maintain age structure (retain older, proportionately more fecund individuals), protect key habitats, and reduce bycatch. MPAs are used sporadically in management of fisheries and are generally based on predicted responses for populations of exploited taxa. However, identification of representative, rare, and high diversity areas of temperate and boreal marine systems, especially on outer continental shelves, is still in its infancy. There is information available from both the scientific literature and from fishers on the life history and behavior of economically important species, on species assemblage patterns, and on physical structure of the marine environment. Such information could be used as a starting point for identifying areas of particular importance to populations or communities of fishes and for the conservation of diversity at the regional scale. Identification of such areas could serve as a basis to design an experimental network of MPAs. Such MPAs, designated for the purpose of maintaining or developing sustainable fisheries, must explicitly be designed within an experimental context, maintaining flexibility for changes in regulations as new information becomes available. Monitoring change in exploited and non-target populations (intra- and inter-guild), habitat complexity indices, and diversity of sentinel taxa (for assessing maintenance of diversity) will be needed to provide feedback to assess the efficacy of MPAs and to recommend changes in the regulatory framework.

Fish species and community distributions as proxies for seafloor habitat distributions: The Stellwagen Bank National Marine Sanctuary example (Northwest Atlantic, Gulf of Maine)

Defining the habitats of fishes and associated fauna on outer continental shelves is problematic given the paucity of data on the actual types and distributions of seafloor habitats. However many regions have good data on the distributions of fishes from resource surveys or catch statistics because of the economic importance of the fisheries. Fish distribution data (species or communities) have been used as a proxy for the distribution of habitats to develop precautionary conservation strategies for habitat protection (e.g., marine protected areas, fishing gear restrictions). In this study we assessed the relationships between the distributions of fish communities and species derived from trawl survey data with the spatial distribution of sediment types determined by sampling and acoustic reflectance derived from multibeam sonar surveys in Stellwagen Bank National Marine Sanctuary. Fish communities were correlated with reflectance values but all communities did not occur in unique sediment types. This suggests that use of community distributions as proxies for habitats should include the caveat that a greater number of communities within an area could indicate a greater range of habitat types. Single species distributions showed relationships between abundance and reflectance values. Trawl catches with low abundances had wide variations in reflectance values while those with high abundances had narrower ranges indicating habitat affinities. Significant non-random frequency-dependent relationships were observed for 17 of 20 species although only 12 of 20 species had significant relationships based on rank correlation. These results suggest that species distributions based on trawl survey data can be used as proxies for the distribution of seafloor habitats. Species with known habitat associations can be used to infer habitat requirements of co-occurring species and can be used to identify a range of habitat types.

Effects of mat morphology on large Sargassum-associated fishes: observations from a remotely operated vehicle (ROV) and free-floating video camcorders

Vagile large juvenile and adult fishes are often under-represented in traditional sampling of Sargassum–associated fishes in the open ocean. We used underwater video recordings from free-floating camcorders and a remotely operated vehicle (ROV) to assess the relative abundance of large mobile fishes under large Sargassum mats (> 10 m diameter), under dispersed clumps of Sargassum (< 1 m diameter), and in open water without Sargassum as a reference. In addition, we conducted dipnet sampling in each Sargassum treatment for a comparison to traditional methods. All samples were obtained in September 1992 along the western wall of the Gulf Stream off Cape Hatteras, North Carolina. A total of 31 fish taxa were identified from both video and dipnet collections. Only 8 taxa were identified in both video and dipnet collections, while 11 taxa were seen only in video and 10 were only found in dipnet collections. Dipnet collections were dominated by juvenile balistids and other small, cryptic fishes, while the video observations were mainly of larger, rapidly-moving carangids. Fish diversity increased with the amount of continuous Sargassum habitat: four taxa were observed when no Sargassum was present, 12 under clumps, and 19 under mats. Our results indicated that mat morphology significantly affects the Sargassum–associated fishes, and that both video and traditional capture methods are complementary and should be used together to accurately census this community.