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USGS2021

Identification of the Gulf of Mexico as an important high-use habitat for leatherback turtles from Central America

Endangered leatherback sea turtles ( Dermochelys coriacea ) are wide-ranging, long-distance migrants whose movements are often associated with environmental cues. We examined the spatial distribution and habitat use for 33 satellite-tracked leatherbacks from nesting beaches on the Caribbean coast of Costa Rica and Panama from 2004 to 2018, an important nesting population for the leatherback Northwest Atlantic Distinct Population Segment. Tracking revealed the use of two distinct regions, the Gulf of Mexico (GoM, n = 18) and the North Atlantic Ocean (NAO, n = 15). We developed density utilization maps to elucidate high-use habitats, migration pathways, and seasonal movements. GoM leatherbacks were found in three concentrated high-use habitats connected by a migration pathway, while NAO leatherbacks were primarily found in a single, large high-use habitat. Leatherbacks in both regions have the potential to interact with Atlantic pelagic longline fisheries based on seasonal overlap with high fishing effort. Our findings suggest that the GoM is an important destination for leatherbacks from the Caribbean coast of Central America with seasonal movements between high-use habitats within the GoM. While leatherbacks are utilizing high-use habitats in both the NAO and the GoM, the proportion of individuals migrating into the GoM increased over the study period. Additionally, NAO leatherbacks have increased the distance they travel in the first 90 d. Regional differences in movement and spatial distribution of high-use habitats are important considerations when developing conservation plans for the Northwest Atlantic leatherback population.

Ecosphere↗

USGS2023

An amplicon genotyping panel suitable for species identification and population genetics in sauger (Sander canadensis) and walleye (Sander vitreus)

Sauger ( Sander canadensis ) and walleye ( Sander vitreus ) are closely related North American fish species that are often managed by fishery agencies throughout their ranges. However, genotyping resources for sauger are presently limited to a small set of microsatellite loci. We evaluated whether primers in an existing walleye genotyping-in-thousands panel could amplify single nucleotide polymorphism loci (SNPs) in sauger. We identified 71 primer pairs that amplify 118 SNPs in both species. Allele frequency differences were large enough to confidently distinguish the species and identify hybrids. Additionally, we identified 41 loci with observed heterozygosity > 0.1 in sauger; these markers may be useful for simple population genetic analyses and parentage analysis when few contributors are present and for differentiating highly structured populations.

Minnesota, Wisconsin↗

USGS2002

Migration and habitats of diadromous Danube River sturgeons in Romania: 1998-2000

Upstream migrant adults of stellate sturgeon, Acipenser stellatus (10 in 1998, 43 in 1999) and Russian sturgeon, A. gueldenstaedtii (three in 1999) were captured at river km (rkm) 58-137, mostly in the spring, and tagged with acoustic tags offering a reward for return. The overharvest was revealed by tag returns (38% in 1998, 28% in 1999) and by harvest within 26 days (and before reaching spawning grounds) of the six stellate sturgeon tracked upstream. A drop-back of > 50% of the tagged sturgeon, some to the Black Sea, shows a high sensitivity to interruption of migration and capture/handling/holding. Harvesting and dropback prevented tracking of sturgeon to spawning sites. Gillnetting and tracking of stellate sturgeon showed that the autumn migration ended in early October (river temperature 16??C) and identified a likely wintering area at river km (rkm) 75-76 (St George Branch). Thus, fishery harvesting after early October captures wintering fish, not migrants. Rare shoreline cliffs in the lower river likely create the only rocky habitat for sturgeon spawning. A survey for potential spawning habitats found five sites with rocky substrate and moderate water velocity, all ???rkm 258. Drift netting caught early life-stages of 17 fish species and one sturgeon, a beluga, Huso huso, larva likely spawned at ???rkm 258. All diadromous Danube sturgeons likely spawn at ???rkm 258.

Journal of Applied Ichthyology↗

USGS2015

Underwater videography outperforms above-water videography and in-person surveys for monitoring the spawning of Devils Hole Pupfish

The monitoring of threatened and endangered fishes in remote environments continues to challenge fisheries biologists. The endangered Devils Hole Pupfish Cyprinodon diabolis , which is confined to a single warm spring in Death Valley National Park, California–Nevada, has recently experienced record declines, spurring renewed conservation and recovery efforts. In February–December 2010, we investigated the timing and frequency of spawning in the species' native habitat by using three survey methods: underwater videography, above-water videography, and in-person surveys. Videography methods incorporated fixed-position, solar-powered cameras to record continuous footage of a shallow rock shelf that Devils Hole Pupfish use for spawning. In-person surveys were conducted from a platform placed above the water's surface. The underwater camera recorded more overall spawning throughout the year (mean ± SE = 0.35 ± 0.06 events/sample) than the above-water camera (0.11 ± 0.03 events/sample). Underwater videography also recorded more peak-season spawning (March: 0.83 ± 0.18 events/sample; April: 2.39 ± 0.47 events/sample) than above-water videography (March: 0.21 ± 0.10 events/sample; April: 0.9 ± 0.32 events/sample). Although the overall number of spawning events per sample did not differ significantly between underwater videography and in-person surveys, underwater videography provided a larger data set with much less variability than data from in-person surveys. Fixed videography was more cost efficient than in-person surveys (\$1.31 versus \$605 per collected data-hour), and underwater videography provided more usable data than above-water videography. Furthermore, video data collection was possible even under adverse conditions, such as the extreme temperatures of the region, and could be maintained successfully with few study site visits. Our results suggest that self-contained underwater cameras can be efficient tools for monitoring remote and sensitive aquatic ecosystems.

Nevada↗

USGS2019

Puerto Rico Sicydium goby diversity: Species-specific insights on population structures and distributions

Sicydiine gobies are major contributors to Caribbean stream fish biodiversity, and ecosystem functions and services. In the Caribbean, Sicydiine gobies are represented by a single genus, Sicydium, but species-level Sicydium taxonomy and distributions remain unresolved in this region. A previous study posited that four species of Sicydium are present in Puerto Rico, including the recently described Sicydium gilberti; however, that study relied solely on morphological characters, and samples from a limited number of locations. Identification of Sicydium to species in studies with more comprehensive sampling has not occurred due to the impracticality of field identification. In our study, we employed morphological data and Mitochondrial Cytochrome C Oxidase I (mtCOI) genetic sequence data, collected from over 500 Sicydium spp. individuals at 16 broadly distributed sites, to provide an inventory of the species of Sicydium that occur in Puerto Rico. Additionally, we reveal new information on the spatial patterns of distribution, relative abundance, population structure, and observed molecular diversity among Sicydium taxa in Puerto Rico’s river systems. This information is essential to advance ecological and evolutionary knowledge of Caribbean fish assemblages, guide stream fish conservation, and for effective management of fisheries.

Neotropical Biodiversity↗

USGS2011

Microbial consortia of gorgonian corals from the Aleutian islands

Gorgonians make up the majority of corals in the Aleutian archipelago and provide critical fish habitat in areas of economically important fisheries. The microbial ecology of the deep-sea gorgonian corals Paragorgea arborea, Plumarella superba , and Cryogorgia koolsae was examined with culture-based and 16S rRNA gene-based techniques. Six coral colonies (two per species) were collected. Samples from all corals were cultured, and clone libraries were constructed from P. superba and C. koolsae . Cultured bacteria were dominated by the Gammaproteobacteria , especially Vibrionaceae , with other phyla comprising <6% of the isolates. The clone libraries showed dramatically different bacterial communities between corals of the same species collected at different sites, with no clear pattern of conserved bacterial consortia. Two of the clone libraries (one from each coral species) were dominated by Tenericutes , with Alphaproteobacteria dominating the remaining sequences. The other libraries were more diverse and had a more even distribution of bacterial phyla, showing more similarity between genera than within coral species. Here we report the first microbiological characterization of P. arborea, P. superba , and C. koolsae .

Alaska↗

USGS2022

Distributions of Cisco (Coregonus artedi) in the upper Great Lakes in the mid-twentieth century, when populations were in decline

The restoration of the once abundant Cisco ( Coregonus artedi ) is a management interest across the Laurentian Great Lakes. To inform the restoration, we (1) described historical distributions of Cisco and (2) explored whether non-indigenous Rainbow Smelt ( Osmerus mordax ) and Alewife ( Alosa pseudoharengus ) played a role in the decline of Cisco populations across the upper Great Lakes (i.e., Lakes Superior, Michigan, and Huron). Our source data were collected from fishery-independent surveys conducted by the U.S. Fish and Wildlife Service’s research vessel R/V Cisco in 1952–1962. By analyzing data collected by gill-net surveys, we confirmed the importance of embayment and shallow-water habitats to Cisco. We found that Cisco was abundant in Whitefish Bay and Keweenaw Bay, Lake Superior, and in Green Bay, Lake Michigan, but we also found a sign of Cisco extirpation in Saginaw Bay, Lake Huron. Our results also showed that Ciscoes generally stayed in waters <80 m in bottom depth throughout the year. However, a substantial number of Ciscoes stayed in very deep waters (>150 m in bottom depth) in summer and fall in Lake Michigan, although we cannot exclude the possibility that these Ciscoes had hybridized with the other Coregonus species. By comparing complementary data collected from bottom-trawl surveys, we concluded that the spatiotemporal overlap between Rainbow Smelt and Cisco likely occurred across the upper Great Lakes throughout 1952–1962. These data were consistent with the hypothesis that Rainbow Smelt played a role in the decline of Cisco populations across the upper Great Lakes in the period. We also found that the spatiotemporal overlap between Alewife and Cisco likely occurred only in Saginaw Bay in fall 1956 and in Lake Michigan after 1960. Thus, any potential recovery of Cisco after the 1950s could have been inhibited by Alewife in Lakes Michigan and Huron.

Lake Huron, Lake Michigan, Lake Superior↗

USGS2016

Behavior patterns and fates of adult steelhead, Chinook salmon, and coho salmon released into the upper Cowlitz River Basin, 2005–09 and 2012, Washington

A multiyear radiotelemetry evaluation was conducted to monitor adult steelhead ( Oncorhynchus mykiss ), Chinook salmon ( O. tshawytscha ), and coho salmon ( O. kisutch ) behavior and movement patterns in the upper Cowlitz River Basin. Volitional passage to this area was eliminated by dam construction in the mid-1960s, and a reintroduction program began in the mid-1990s. Fish are transported around the dams using a trap-and-haul program, and adult release sites are located in Lake Scanewa, the uppermost reservoir in the system, and in the Cowlitz and Cispus Rivers. Our goal was to estimate the proportion of tagged fish that fell back downstream of Cowlitz Falls Dam before the spawning period and to determine the proportion that were present in the Cowlitz and Cispus Rivers during the spawning period. Fallback is important because Cowlitz Falls Dam does not have upstream fish passage, so fish that pass the dam are unable to move back upstream and spawn. A total of 2,051 steelhead and salmon were tagged for the study, which was conducted during 2005–09 and 2012, and 173 (8.4 percent) of these regurgitated their transmitter prior to, or shortly after release. Once these fish were removed from the dataset, the final number of fish that was monitored totaled 1,878 fish, including 647 steelhead, 770 Chinook salmon, and 461 coho salmon. Hatchery-origin (HOR) and natural-origin (NOR) steelhead, Chinook salmon, and coho salmon behaved differently following release into Lake Scanewa. Detection records showed that the percentage of HOR fish that moved upstream and entered the Cowlitz River or Cispus River after release was relatively low (steelhead = 38 percent; Chinook salmon = 67 percent; coho salmon = 41 percent) compared to NOR fish (steelhead = 84 percent; Chinook salmon = 82 percent; coho salmon = 76 percent). The elapsed time from release to river entry was significantly lower for NOR fish than for HOR fish for all three species. Tagged fish entered the Cowlitz River in greater proportions than the Cispus River, regardless of origin. We found that 23–47 percent of the HOR fish entered the Cowlitz River and 12–38 percent entered the Cispus River. Similarly, 67–70 percent of the NOR fish entered the Cowlitz River and 38–66 percent entered the Cispus River. These behavioral differences translated into similar differences in fates during the spawning periods as higher percentages of tagged fish were assigned Cowlitz River fates than Cispus River fates. Fallback rates were affected by fish origin and release site. Overall, 12 percent of steelhead, 19 percent of Chinook salmon, and 8 percent of coho salmon fell back downstream of Cowlitz Falls Dam prior to spawning. Fallback rates were lower for fish that were released in the Cowlitz River or the Cispus River than for reservoir-released fish, but statistical comparisons were not robust because of small sample sizes at the river release sites. Fallback rates for fish released at the river release sites were 10 percent lower for steelhead, 4 percent lower for Chinook salmon, and 9 percent lower for coho salmon than for reservoir-released fish. However, fallback rates also were different between HOR and NOR fish. Fallback rates were significantly higher for HOR reservoir-released fish than for NOR reservoir-released fish. This study provided data that were insightful for understanding behavior and movement patterns in the upper Cowlitz River Basin and yielded estimates of fallback rates and fish fates that may be useful for fishery managers in the years to come. Studies from other systems have shown that factors such as prespawn mortality and fallback have resulted in substantial losses to spawning populations where trap-and-haul programs are being used as a restoration tool. Future research in the upper Cowlitz River Basin may use additional telemetry studies, genetic analyses, and spawning ground surveys to provide answers for new questions and to continue to monitor the progress of the reintroduction effort.

Washington↗

USGS1969

Insecticides and the Great Lakes

Cracks in the perfect image of DDT appeared when traces of the insecticide began to show up in a wide variety of organisms throughout the world. As more and more people investigated this problem, it became increasingly evident that terrestrial and aquatic animals were accumulating comparatively high concentrations of DDT from extremely low levels in their environment. It also became apparent that DDT and all of the other chlorinated hydrocarbon insecticides were not species-specific, but were toxic to all forms of animal life including man. In 1965, when the Great Lakes Fishery Laboratory of the U.S. Bureau of Commercial Fisheries began to monitor pesticide residues in fish from the Great Lakes, it was discovered that the fish contained not only DDT, but also dieldrin, another chlorinated hydrocarbon insecticide. Fish from Lake Michigan in particular contained relatively high levels of both of these insecticides; concentrations of DDT were in the parts per million (ppm) range, a factor at least several million times greater than the few parts per trillion found in the water. Two questions presented themselves: first, How did these insecticides get into the water? and second, How did the fish build up such high concentrations in their bodies from such low concentrations in the water?

Limnos↗

USGS2016

United States Biological Survey: A compendium of its history, personalities, impacts, and conflicts

In 1885, a small three-person unit was created in the U.S. Department of Agriculture to gather and analyze information on bird migrations. Originally called the Section of Economic Ornithology, over the next 55 years this unit underwent three name changes and accumulated ever-increasing responsibilities for the nation’s faunal resources. Transferred to the Department of the Interior in 1939, this agency was merged with the Bureau of Fisheries in 1940 to create the U.S. Fish and Wildlife Service (FWS). The following account details the chronology, directorship, and growth of the U.S. Bureau of Biological Survey up to its renovation as the FWS. This account also profiles some employees of the Biological Survey.

Book↗

USGS2022

Final report: Understanding historical and predicting future lake temperatures in North and South Dakota

Lakes, reservoirs, and ponds are central and integral features of the landscape of the North Central US. These water bodies provide aesthetic, cultural, and ecosystem services to surrounding wildlife and human communities. Lakes are warming, resulting in the loss of many native fish. In order to manage economically valuable fisheries and other ecosystem services provided by lakes, it is important for managers to have access to accurate estimates of water temperature to better understand past change and to plan for potential future further warming. These data are invaluable for making decisions such as whether to continue stocking plans as usual in certain lakes or how to set specific harvest limits. This project developed new state-of-the-art methods to model historical thermal habitat for thousands of lakes in the Midwest US.

North Dakota, South Dakota↗

USGS2022

Distribution of niclosamide following granular Bayluscide applications in lotic systems

The granular formulation of Bayluscide [Bayluscide 3.2% Granular Sea Lamprey Larvicide, granular Bayluscide (gB)] is applied in lentic and lotic systems to survey (assessment) and kill (treatment) larval sea lampreys ( Petromyzon marinus ; Linnaeus, 1758) in the Great Lakes basin. Granules are spread on the water surface, settle to the sediment surface, and dissolve. The potential risk of niclosamide exposure (2′,5-dichloro-4′-nitrosalicylanilide), the active ingredient of gB, to non-target organisms located downstream of survey plots, is a concern of partner agencies (state-level natural resource departments, U.S. Fish and Wildlife Service Ecological Services, and Fisheries and Oceans Canada Species at Risk Branch). Spatiotemporal distribution of niclosamide in the water column and sediment was evaluated in and downstream of five larval survey plots in two rivers following the application of gB. Water samples were collected at 0.25, 2, 4, 6, 8, and 24 h from three depths in the water column (10 cm above the sediment, ½ the water column depth, and the water surface) at three locations inside each survey plot, and 1 meter upstream from three sediment sample grids positioned 10, 30, and 100 m downstream. Sediment samples were collected from inside the grids at 0.25, 2, 4, 6, 8, and 24 h, and from inside the survey plots, 8 and 24 h after gB application. Niclosamide was detected in the sediment and water at all sample locations. From 2 to 24 h after application, average water concentrations 1) varied between study sites, 2) decreased from the survey plots to 100 m downstream, 3) varied by depth in the water column, and 4) decreased over time. Average sediment concentrations varied by distance downstream and time post-application, but not by study site or river. Data suggest there would be negligible exposure to non-target organisms downstream of a gB survey plot based on low niclosamide concentrations measured in the water and sediment. The depletion rate of niclosamide was also evaluated in St. Clair River sediment dosed at the field application rate. Niclosamide concentration decreased at a rate of 2.28% per hour over the 24 hours measured, equating to a half-life of 1.27 days. This indicates the length of time an organism in the sediment in a survey plot might be exposed. Underwater cameras were placed along the edge of two St. Clair River survey plots to document gB distribution on the sediment and any potential target and non-target effects. Video was inconclusive in tracking gB through the water column. Larval sea lamprey and non-target mortality were not observed. Additional video footage of one St. Clair River survey plot showed large areas of river bottom without gB.

Michigan↗

USGS2000

Ecology and biology of paddlefish in North America: historical perspectives, management approaches, and research priorities

Paddlefish ( Polyodon spathula , Polyodontidae)are large, mostly-riverine fish that once were abundant in medium- to large-sized river systems throughout much of the central United States. Concern for paddlefish populations has grown from a regional fisheries issue to one of national importance for the United States. In 1989, the U.S. Fish and Wildlife Service (USFWS) was petitioned to list paddlefish as a federally threatened species under the Endangered Species Act. The petition was not granted, primarily because of a lack of empirical data on paddlefish population size, age structure, growth, or harvest rates across the present 22-state range. Nonetheless, concern for paddlefish populations prompted the USFWS to recommend that paddlefish be protected through the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). The addition of paddlefish to Appendix II of CITES, which was approved in March 1992, provides a mechanism to curtail illegal trade in paddlefish and their parts and supports a variety of conservation plans. Paddlefish populations have been negatively affected by overharvest, river modifications, and pollution, but the paddlefish still occupies much of its historic range and most extant populations seem to be stable. Although many facets of paddlefish biology and ecology are well understood, the lack of information on larval and juvenile ecology, mechanisms that determine recruitment, population size and vital rates, interjurisdictional movements, and the effects of anthropogenic activities present significant obstacles for managing paddlefish populations. Questions about the size and structure of local populations, and how such populations are affected by navigation traffic, dams, and pollution are regarded as medium priority areas for future research. The availability of suitable spawning habitat and overall reproductive success in impounded rivers are unknown and represent critical areas for future research. Research on reproductive and recruitment success in impounded rivers have significant implications for managing paddlefish, as rivers are modified further for human use.

Reviews in Fish Biology and Fisheries↗

USGS2021

Environmental factors influencing annual sucker (Catostomus sp.) migration into a Great Lakes tributary

Fish migration in rivers is a growing area of concern as mounting anthropogenic influences, particularly fragmentation from dams and barriers, constitute major threats to global river species diversity. Barriers can impede the movement of fishes between areas critical to the completion of their lifecycle, affecting both population and ecosystem viability. In response, fish passage solutions have been identified as a critical need to maintain fisheries viability in the Laurentian Great Lakes, and around the world. Pivotal to the success of these fish passage solutions is a more complete understanding of the movement phenology and environmental cues that instigate migration. We used a dual-frequency identification sonar (DIDSON) to evaluate environmental triggers of river entry during spring and summer for three size classes of migratory fishes in the Boardman River, a Lake Michigan tributary. Our results indicate that medium size fish (>30 cm and < 50 cm), primarily composed of white sucker Catostomus commersonii and longnose sucker Catostomus catostomus were 21% more likely to enter the river at sunset and 25% less likely at midnight in comparison to midday. Entry rates of medium fish increased 6% for every 1 °C increase in river temperature, 4% for every 1 m 3 /s increase in river discharge from the day prior, and were reduced by 1% for every 10 cm increase in lake level. Understanding these processes in the tributaries of the Great Lakes is important to inform the fish passage solutions currently being developed for the Boardman River, and to inform management regulations for Great Lakes migratory fishes.

Michigan↗

USGS2013

Environmental stressors afflicting tailwater stream reaches across the United States

The tailwater is the reach of a stream immediately below an impoundment that is hydrologically, physicochemically and biologically altered by the presence and operation of a dam. The overall goal of this study was to gain a nationwide awareness of the issues afflicting tailwater reaches in the United States. Specific objectives included the following: (i) estimate the percentage of reservoirs that support tailwater reaches with environmental conditions suitable for fish assemblages throughout the year, (ii) identify and quantify major sources of environmental stress in those tailwaters that do support fish assemblages and (iii) identify environmental features of tailwater reaches that determine prevalence of key fish taxa. Data were collected through an online survey of fishery managers. Relative to objective 1, 42% of the 1306 reservoirs included in this study had tailwater reaches with sufficient flow to support a fish assemblage throughout the year. The surface area of the reservoir and catchment most strongly delineated reservoirs maintaining tailwater reaches with or without sufficient flow to support a fish assemblage throughout the year. Relative to objective 2, major sources of environmental stress generally reflected flow variables, followed by water quality variables. Relative to objective 3, zoogeography was the primary factor discriminating fish taxa in tailwaters, followed by a wide range of flow and water quality variables. Results for objectives 1–3 varied greatly among nine geographic regions distributed throughout the continental United States. Our results provide a large-scale view of the effects of reservoirs on tailwater reaches and may help guide research and management needs.

River Research and Applications↗

USGS1999

Management implications of fish trap effectiveness in adjacent coral reef and gorgonian habitats

A combination of visual census and trap sampling in St. John, USVI indicated that traps performed better in gorgonian habitat than in adjacent coral reef habitat. Although most families were seen more commonly in coral habitat, they were caught more often in gorgonian areas. Traps probably fished more effectively in gorgonian habitats, especially for migrating species, because traps provided shelter in the relatively topographically uniform environment of gorgonian dominated habitats. Recently, trap fishermen on St. John have been moving effort away from traditionally fished nearshore coral reefs and into a variety of more homogeneous habitats such as gorgonian habitat. Consequently, exploitation rates of the already over-harvested reef fish resources may be increasing. Reef fish managers and marine reserve designers should consider limiting trap fishing in gorgonian habitats to slow the decline of reef fisheries.

Environmental Biology of Fishes↗

USGS2013

Self-reporting bias in Chinook salmon sport fisheries in Idaho: implications for roving creel surveys

Self-reporting bias in sport fisheries of Chinook Salmon Oncorhynchus tshawytscha in Idaho was quantified by comparing observed and angler-reported data. A total of 164 observed anglers fished for 541 h and caught 74 Chinook Salmon. Fifty-eight fish were harvested and 16 were released. Anglers reported fishing for 604 h, an overestimate of 63 h. Anglers reported catching 66 fish; four less harvested and four less released fish were reported than observed. A Monte Carlo simulation revealed that when angler-reported data were used, total catch was underestimated by 14–15 fish (19–20%) using the ratio-of-means estimator to calculate mean catch rate. Negative bias was reduced to six fish (8%) when the means-of-ratio estimator was used. Multiple linear regression models to predict reporting bias in time fished had poor predictive value. However, actual time fished and a categorical covariate indicating whether the angler fished continuously during their fishing trip were two variables that were present in all of the top a priori models evaluated. Underreporting of catch and overreporting of time fished by anglers present challenges when managing Chinook Salmon sport fisheries. However, confidence intervals were near target levels and using more liberal definitions of angling when estimating effort in creel surveys may decrease sensitivity to bias in angler-reported data.

North American Journal of Fisheries Management↗

USGS2004

Role of a large marine protected area for conserving landscape attributes of sand habitats on Georges Bank (NW Atlantic)

Mobile fishing gear reduces seafloor habitat complexity through the removal of structure-building fauna, e.g. emergent organisms that create pits and burrows, as well as by smoothing of sedimentary bedforms (e.g. sand ripples). In this study, we compared the relative abundance of microhabitat features (the scale at which individual fish associate with seafloor habitat) inside and outside of a large fishery closed area (6917 km 2 ) on Georges Bank. Starting in late 1994, the closed area excluded all bottom tending fishing gear capable of capturing demersal fishes. A total of 32 stations were selected inside and outside of the closed area in sand habitats. Video and still photographic transects were conducted at each station using the Seabed Observation and Sampling System (SEABOSS). Seven common (i.e. featureless sand, rippled sand, sand with emergent fauna, bare gravelly sand, gravelly sand with attached-erect fauna, whole shell, shell fragment) and 2 rare (sponges, biogenic depressions) microhabitat types were compared separately. Results showed significant differences in the relative abundance of the shell fragment and sponge microhabitat types between fished and unfished areas. The lack of differences for the other microhabitats may indicate that the level of fishing activity in the area is matched by the system's ability to recover.

Georges Bank↗