97 research outputs found
Response of Coastal Fishes to the Gulf of Mexico Oil Disaster
The ecosystem-level impacts of the Deepwater Horizon disaster have been largely unpredictable due to the unique setting and magnitude of this spill. We used a five-year (2006–2010) data set within the oil-affected region to explore acute consequences for early-stage survival of fish species inhabiting seagrass nursery habitat. Although many of these species spawned during spring-summer, and produced larvae vulnerable to oil-polluted water, overall and species-by-species catch rates were high in 2010 after the spill (1,989±220 fishes km-towed−1 [μ ± 1SE]) relative to the previous four years (1,080±43 fishes km-towed−1). Also, several exploited species were characterized by notably higher juvenile catch rates during 2010 following large-scale fisheries closures in the northern Gulf, although overall statistical results for the effects of fishery closures on assemblage-wide CPUE data were ambiguous. We conclude that immediate, catastrophic losses of 2010 cohorts were largely avoided, and that no shifts in species composition occurred following the spill. The potential long-term impacts facing fishes as a result of chronic exposure and delayed, indirect effects now require attention
Hydrokinetic Turbine Effects on Fish Swimming Behaviour
Hydrokinetic turbines, targeting the kinetic energy of fast-flowing currents, are under development with some turbines
already deployed at ocean sites around the world. It remains virtually unknown as to how these technologies affect
fish, and rotor collisions have been postulated as a major concern. In this study the effects of a vertical axis
hydrokinetic rotor with rotational speeds up to 70 rpm were tested on the swimming patterns of naturally occurring
fish in a subtropical tidal channel. Fish movements were recorded with and without the rotor in place. Results showed
that no fish collided with the rotor and only a few specimens passed through rotor blades. Overall, fish reduced their
movements through the area when the rotor was present. This deterrent effect on fish increased with current speed.
Fish that passed the rotor avoided the near-field, about 0.3 m from the rotor for benthic reef fish. Large predatory fish
were particularly cautious of the rotor and never moved closer than 1.7 m in current speeds above 0.6 ms-1. The
effects of the rotor differed among taxa and feeding guilds and it is suggested that fish boldness and body shape
influenced responses. In conclusion, the tested hydrokinetic turbine rotor proved non-hazardous to fish during the
investigated conditions. However, the results indicate that arrays comprising multiple turbines may restrict fish
movements, particularly for large species, with possible effects on habitat connectivity if migration routes are
exploited. Arrays of the investigated turbine type and comparable systems should therefore be designed with gaps of
several metres width to allow large fish to pass through. In combination with further research the insights from this
study can be used for guiding the design of hydrokinetic turbine arrays where needed, so preventing ecological
impacts
Species composition and habitat preferences of the nearshore fish fauna of Bonne Bay, Newfoundland
Determining biodiversity baseline is the first step toward establishing species monitoring and conservation programs. In this study we report on a 10-year survey of the fish fauna of Bonne Bay, a fjord surrounded by the Gros Morne National Park on the west coast of Newfoundland, Canada. The objectives of our study were: 1) to determine the fish fauna of Bonne Bay using standardized sampling methods; 2) to gather information on the habitats of fishes of conservation concern; and 3) to provide baseline information on Bonne Bay as a potential candidate for a National Marine Conservation Area (NMCA).
Methods
A survey of the fish fauna of the inner Bonne Bay was conducted each summer from 2002 to 2011 at multiple sites representing a range of fish habitats within the fjord. Sampling gears included two types of beach seine, gillnets with various mesh sizes and a bottom trawl. Species composition was statistically compared across sites within the fjord.
Results
We collected and identified 29 fish species from 17 families. Fish assemblages comprised anadromous, estuarine, and marine fish species, including a late-maturing type of winter skate (Leucoraja ocellata) that is rarely found in the adjacent waters of the northern Gulf of St. Lawrence. Similarity in species composition across sites reflected salinity, substrate composition, and presence of eelgrass (Zostera marina), but not the geographic distance between sites.
Conclusions
Bonne Bay’s adjacency to a United Nations Educational, Scientific, and Cultural Organization (UNESCO) World Heritage Site, its diverse fish fauna that includes several species of conservation concern, its potential for education and enjoyment, and its stewardship by local people are suggestive of the future candidacy as a NMCA. The data presented here will help managers assess the potential of Bonne Bay as a National Marine Conservation Area
Limited Vegetation Development on a Created Salt Marsh Associated with Over-Consolidated Sediments and Lack of Topographic Heterogeneity
Restored salt marshes frequently lack the full range of plant communities present on reference marshes, with upper marsh species underrepresented. This often results from sites being too low in the tidal frame and/or poorly drained with anoxic sediments. A managed coastal realignment scheme at Abbotts Hall, Essex, UK, has oxic sediments at elevations at which upper marsh communities would be expected. But 7 years after flooding, it continued to be dominated by pioneer communities, with substantial proportions of bare ground, so other factors must hinder vegetation development at these elevations. The poorly vegetated areas had high sediment shear strength, low water and organic carbon content and very flat topography. These characteristics occur frequently on the upper parts of created marshes. Experimental work is required to establish causal links with the ecological differences, but other studies have also reported that reduced plant β-diversity and lower usage by fish are associated with topographic uniformity. Uniformity also leads to very different visual appearance from natural marshes. On the upper intertidal, sediment deposition rate are slow, water velocities are low and erosive forces are weak. So, topographic heterogeneity cannot develop naturally, even if creeks have been excavated. Without active management, these conditions will persist indefinitely
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