Ecosystem Shock: The Devastating Impacts of Invasive Species on the Great Lakes Food Web

Gives an account of the changes to the Great Lakes ecosystem brought about by non-native aquatic species. Assesses the current and future impacts on fish communities and commercial fisheries. Provides policy and research recommendations

Mangroves enhance the biomass of coral reef fish communities in the Caribbean

Mangrove forests are one of the world's most threatened tropical ecosystems with global loss exceeding 35% (ref. 1). Juvenile coral reef fish often inhabit mangroves, but the importance of these nurseries to reef fish population dynamics has not been quantified. Indeed, mangroves might be expected to have negligible influence on reef fish communities: juvenile fish can inhabit alternative habitats and fish populations may be regulated by other limiting factors such as larval supply or fishing. Here we show that mangroves are unexpectedly important, serving as an intermediate nursery habitat that may increase the survivorship of young fish. Mangroves in the Caribbean strongly influence the community structure of fish on neighbouring coral reefs. In addition, the biomass of several commercially important species is more than doubled when adult habitat is connected to mangroves. The largest herbivorous fish in the Atlantic, Scarus guacamaia, has a functional dependency on mangroves and has suffered local extinction after mangrove removal. Current rates of mangrove deforestation are likely to have severe deleterious consequences for the ecosystem function, fisheries productivity and resilience of reefs. Conservation efforts should protect connected corridors of mangroves, seagrass beds and coral reefs

Assessing Fish Communities and Habitat Dynamics at the North Platte River-Lake Mcconaughy Interface: Implications for Conservation and Management

The river-reservoir interface (RRI) provides dynamic habitat heterogeneity that influences fish communities within the reservoir and the tributary upstream. However, little is known about the North Platte River-Lake McConaughy interface. Thus, the objectives of this research were to: 1) describe fish assemblages in the North Platte River and relate their temporal differences to water quality and physical habitat parameters; and 2) compare young fish communities collected with different gears in the upper reservoir. Twenty-nine species were collected across four habitat types in the North Platte River above Lake McConaughy. Main and side channel habitats were more consistently available throughout the summer. Backwater habitats declined in abundance, and back eddies disappeared. Species richness and Shannon’s diversity were highest in backwaters. Fish communities were somewhat similar between the habitat types, but some species were more or less abundant in some habitats. Water quality did not differ between habitat types. However, discharge and water temperature appeared to influence community composition. In upper Lake McConaughy, I captured 21 taxa across four sampling gears. Fewer species were captured with the gears used in the earlier time period compared to the gears used later time period. Species richness, Shannon’s diversity, and relative abundance were highest for seines and lowest for tow nets. Boat-mounted electrofishing appeared to be the most efficient gear. Similarities were noted in fish communities between the two time periods, but abundance of individual species varied between time periods. This study provides updated and new information on fish communities in the North Platte River-Lake McConaughy system. Selecting the sampling gear or gears that best meet sampling objectives is important for understanding fish communities in RRIs. With such sampling information, fisheries managers may be able to identify water management strategies that provide habitats for fish communities in unique ecotones such as the RRI

Long-Term Trends of Stream Fish Community Assemblages in Southern Missouri with Contemporary Land Use Impacts

Stream fish communities in the Ozarks are structured via a number of different mechanisms, including basin, stream size, and human land use. The purpose of this study was to understand the structuring mechanisms of stream fish communities in southern Missouri. I compiled 48 years of historical fish collections performed by the Ichthyology class at Missouri State University consisting of 140 sites. I resampled 45 of these sites in summer of 2016. First, I tested whether communities are different between basins and stream size. Next, I tested associations of land use at three spatial scales to local fish communities. Last, I used historical collections to determine occupancy of species through time. Contemporary fish communities were used to answer basin, stream size, and land use structuring questions. Bray-Curtis dissimilarities demonstrated that communities in the modern data were different between basin, but not different in relation to stream size. I used Bray-Curtis again to calculate dissimilarity of land use composition at each spatial scale, then compared that to the communities with Mantel tests. Mantel tests showed that differences in land use were associated with differences in fish communities at all three spatial scales. Historical data were used to create logistic regressions for occupancy of each species to determine if presence is increasing or decreasing. Logistic regressions showed many species in decline, especially darters and minnows. This points to a need to more fully understand how fish communities in the Ozarks are impacted by human activities

Role of fish communities in particulate organic matter fluxes between salt marshes and coastal marine waters in the Mont Saint-Michel bay.

Among the 90 fishspecies censused in the Mont Saint-Michel Bay (France), 23 colonise and forage in the salt marshes during flood. Therefore, this environmentmay play an important trophic and nursery role for these species. This community is largely dominated by mullets (81% of the biomass), Liza ramada and secondarily L. aurata. But gobies (mainly Pomatoschistus minutus and P. lozanoï) and sea bass (Dicentrarchus labrax) are also present; they represent respectively 11% and 4% of the biomass. During the tide cycles, mullets export from salt marshes about 7% of their body weight (FW) containing a mixture of sediment (43%), organic matter (24%) and water (33%). Gobies and sea bass mainly feed on dwelling macro-invertebrates, and they export respectively 4.5% and 10% of their body weight during a tide cycle. Thus, we estimated that 50 tonnes year−1 of particulate organic matter (dry weight POM) are exported from the 4000 ha of salt marshes to the marine coastal waters. These fish communities appear to be POM transporters and could play a significant role in the global energy budgets of coastal environments such as Mont Saint-Michel Bay. According to the seasons and the years, the energy exported by fish communities is assumed to range between 0 and 10% of the total POM output

Changes in Fish Communities in the Upper Patuxent River from 1966 to 1977

Ten year comparison of fish survey's with respect to diversity evenness and composition of fish communities. The upper Patuxent River was divided into Piedmont Plateau and Coastal Plain regions, not only for geographical purposes, but also because of the clustering of sewage treatment plants in the Coastal Plain region. In the Piedmont Plateau region, the fish species diversity changed very little from 1966 to 1977 ( Little Patuxent -- 2.82 to 2.66; Middle Patuxent -- 2.86 to 2.83; and main stem -- 2.46 to 2.63), except in a section of Little Patuxent River at and below the City of Columbia where the species diversity index showed a significant reduction from 2.97 to 1.99, and in a section of the main stem Patuxent River immediately downstream from the Brighton Dam of the Triadelphia Reservoir where the index increased significantly from 1.66 to 3.20. In the Coastal Plain region, a significant reduction in the fish species diversity index occurred between 1966 and 1977 below the two sewage treatment plant outfalls : Savage -- 2.69 to 0 and Patuxent-Crofton -- 3.06 to 1.33. Also, the substantial reduction in the species diversity index which had already occurred in 1966 below the six other plant: outfalls of Fort Meade No. I, Fort Meade No. 2, Maryland House of Correction, Maryland City , Parkway and Bowie, remained depressed in 1977. On the other hand, below the Horsepen Sewage Treatment Plant (a tertiary plant practicing dechlorination) the species diversity index increased from 1.91 to 2.8. (PDF contains 48 pages

Assessment of the pelagic fish populations using CEN multi-mesh gillnets: consequences for the characterization of the fish communities

The contribution of CEN standard pelagic nets to the assessment of fish communities is tested by comparing three metrics (species composition, species abundance, and size structures) measured in accordance with the standard (i.e. using benthic nets only) to those calculated from the total effort (i.e. including pelagic nets). Hydroacoustic surveys were used simultaneously to assess fish densities in the pelagic habitat. The results show that in most cases the pelagic nets did not provide any extra information about these three metrics. However, their inclusion in the calculation of CPUE and size structures may affect the picture of the fish communities, especially in lakes containing salmonid populations. This study highlights the need to sample pelagic fish when assessing fish communities in order to determine lake quality