Coastal wetland restoration improves habitat for juvenile sportfish in Tampa Bay,Florida, U.S.A.

Increasing human populations and urban development have led to losses of estuarine habitats for fish and wildlife. Where resource managers are restoring coastal wetlands, in addition to meeting goals related to hydrologic connectivity, biodiversity, and recreational opportunities, efforts are being made to provide habitat that is suitable for juvenile sportfish. An 18‐month study was conducted to compare juvenile sportfish use of natural, restored, and impacted sites along Tampa Bay, Florida, shorelines. Juvenile sportfish densities at restored sites were broadly comparable to natural sites and greater than at impacted sites. However, site‐specific differences in sportfish use did occur within site types. For example, one restored site had significantly higher densities of red drum Sciaenops ocellatus than any other site, while black drum Pogonias cromis were found exclusively at another restored site. To evaluate whether the restored sites are providing suitable habitat for juvenile fish, we assessed growth (estimated from counts of daily rings on otoliths) and condition (determined by lipid analyses) of juvenile common snook Centropomus undecimalis, an archetypal coastal wetland‐dependent species. Growth (0.43–0.56 mm SL/day) and condition (4.6–6.1% lipid of dry weight) exhibited only site‐specific differences and did not vary among natural, restored, and impacted site types. Although mortality rates of juvenile sportfish were not determined, use of a 40‐m seine found that densities of potential piscine predators in these coastal wetlands were relatively low compared to published studies of open estuarine shorelines. The restoration and creation of coastal wetlands in Tampa Bay provides improved habitat for juvenile sportfish.     

Influence of teleost abundance on the distribution and abundance of sharks in Florida Bay, USA

Understanding the factors that influence the distribution and abundance of predators, including sharks, is important for predicting the impacts of human changes to the environment. Such studies are particularly important in Florida Bay, USA where there are planned large-scale changes to patterns of freshwater input from the Everglades ecosystem. Studies of many marine predators suggest that links between predator and prey habitat use may vary with spatial scale, but there have been few studies of the role of prey distribution in shaping habitat use and abundance of sharks. We used longline catches of sharks and trawls for potential teleost prey to determine the influence of teleost abundance on shark abundance at the scale of regions and habitats in Florida Bay. We found that shark catch per unit effort (CPUE) was not linked to CPUE ofteleosts at the scale of sampling sites, but shark CPUE was positively correlated with the mean CPUE for teleosts within a region. Although there does not appear to be a strong match between the abundance of teleosts and sharks at small spatial scales, regional shark abundance is likely driven, at least partially, by the availability of prey. Management strategies that influence teleost abundance will have cascading effects to higher trophic levels in Florida Bay. Electronic Supplementary Material is available for this article at     

Piscivore Responses to Enhancement of the Channelized Kissimmee River,Florida, U.S.A.

Evaluation of the success of ecosystem restoration projects requires identification of appropriate ecological metrics. Comparison of reconstructed food webs (or subsets thereof) from restored and non‐restored habitats may be a valuable tool to evaluate restoration success because food webs help identify critical predator–prey relationships, keystone species, relative importance of direct and indirect trophic interactions, and other aspects of ecological function. We compared the diets of apex predatory fishes collected from enhanced and non‐enhanced portions of the channelized Kissimmee River, Florida, USA to determine whether food web structure responded to experimental hydrologic manipulations. Diets were reconstructed for black crappie (Pomoxis nigromaculatus), bowfin (Amia calva), chain pickerel (Esox niger), Florida gar (Lepisosteus platyrhincus), largemouth bass (Micropterus salmoides), and warmouth (Lepomis gulosus) collected from enhanced and non‐enhanced portions of the Kissimmee River. Prey eaten by apex predatory fishes in the enhanced portion of the Kissimmee River were quantitatively and qualitatively different from prey eaten in non‐enhanced portions of the river. Predators in the enhanced portion of the river had fewer empty stomachs, more prey items per individual, more prey types per individual, more fish prey per individual, greater overall richness of prey, and a multivariate suite of prey distinct from predators in non‐enhanced portions of the river. Results from hydrologic manipulations suggest that large‐scale restoration of hydrologic linkages between the main channel and floodplain habitats will positively affect food web structure and ecosystem function in the Kissimmee River.     

Stream channel geomorphology influences mussel abundance in southern Appalachian streams, U.S.A.

1. Studies of North American streams have shown that hydraulic parameters and stream geomorphology can explain unionid mussel abundance at both the reach and catchment scale. However, few studies have examined applicability of hydrogeomorphic variables across broader spatial scales, such as across whole catchments, or have elucidated conditions under which spates can affect mussel populations in streams. 2. We quantified freshwater mussel abundance and species richness and their physical habitat at 24 sites in eight streams in southern Appalachian catchments in 2000 and 2001. In addition, we modelled site‐specific hydraulic parameters during summer baseflow and bankfull stages to estimate high‐ and low‐discharge conditions, respectively. 3. Mussel abundance was related to stream geomorphology, whereas richness was related to stream size. Baseflow habitat parameters explained only minor variation in abundance or richness, and both measures were highly correlated with mean current velocity or stream size. Bankfull shear stress composed a relatively low proportion of overall mussel habitat variability, but it accounted for significant variation in abundance and richness. 4. Mussel abundance was highly variable at sites subject to low‐shear stress during spates, whereas abundance always was low at sites subject to high‐shear stress. These data suggest that habitat conditions during floods, rather than those at summer baseflow, limit the abundance of mussels in Appalachian streams. These data also suggest that mussel abundance and assemblage structure may be sensitive to any changes in channel geomorphology and hydraulic conditions that might result from land use in the catchment.     

Bivalve enhancement and restoration strategies in Florida,U.S.A.

In Florida, U.S.A. populations of recreationally and commercially important bivalve molluscs are stressed by a variety of factors, including habitat degradation, overfishing and development. Bivalves such as the bay scallop, Argopecten irradians, and the hard clam, Mercenaria spp., are uniquely positioned to benefit from restoration and enhancement activities because of the physical setting in which they live or because of recent efforts to restore habitat. For bay scallops, a major restoration effort has been implemented on the west coast of Florida. Adult scallops are collected from the target site and spawned in the laboratory. The offspring are cultured in ponds until they reach an average shell height of approximately 30 mm and then are planted in cages at the target site from which the parents were collected. Parents and offspring are genetically monitored, as are new recruits sampled at a variety of sites along the coast. The ultimate goal of this restoration program is to create concentrated patches of spawners that will supply recruits to west Florida seagrass beds. For hard clams, three different strategies are being tested to determine the most ecologically and economically feasible approach to use to enhance harvestable clam populations. Hard clams are occasionally abundant in the Indian River lagoon on the east central coast of the state, but transportation causeways fragment the lagoon into a series of basins that are largely isolated from one another. At any time, only a subset of the basins that compose the lagoon may be environmentally suitable for supporting the sensitive larval and juvenile stages of hard clams, and the members of that subset change constantly as environmental conditions change in the lagoon. Transplanting spawner stock, seeding juveniles under a variety of protective treatments, and injecting fertilized eggs directly into the lagoon are each being tested for their effectiveness in exploiting environmentally appropriate conditions and producing successful settlement events. Each strategy is being tested for its ecological and economic suitability, and the most appropriate strategy will be implemented in an effort to maintain clam abundance at a level where licensed clammers in the Indian River region can realize a minimum income from the fishery, even when naturally recruiting clam stocks are depleted.     

Evidence for sexual dichromatisms in spawning aggregations of yellowfin grouper Mycteroperca venenosa and tiger grouper Mycteroperca tigris from the southern Gulf of Mexico

Colour pattern characteristics and gonad histology were used to detect sexual dichromatisms in yellowfin grouper Mycteroperca venenosa and tiger grouper Mycteroperca tigris from the Campeche Bank, Mexico. Specimens were obtained from commercial catches between March and May during 2002 and 2004. All specimens were examined dead. Ninety-seven per cent of males had different sex-associated colour patterns. Male yellowfin grouper displayed a bright yellow blotch on both sides of the lower jaw while females retained a reddish lower jaw. Male tiger grouper had uniform dark pectoral fins while females had bright orange pectoral fins. In situ observations of live fishes at fishing sites showed the lower jaw and pectoral fin colourations to be clearly visible underwater at a depth of 35 m. All males of both species and most females (80% yellowfin grouper and 98% tiger grouper) were sexually active and probably caught during their spawning season. This suggests that distinct colourations observed for male M. venenosa and M. tigris may be seasonal displays associated with spawning. Both the lower jaw and pectoral fin colourations were still visible in dead fishes after several days on ice. Differences observed for ray length of exserted vertical fins in tiger grouper specimens were probably not a sex-associated characteristic.     

Comparison of abundance and habitat usage for common bottlenose dolphins between sites exposed to differential anthropogenic stressors within the estuaries of southern Georgia,U.S.A

The health of common bottlenose dolphins (Tursiops truncatus) within southern Georgia estuaries is of particular concern due to high levels of anthropogenic contaminants in their tissues. Dolphins in this region have the highest polychlorinated biphenyl (PCB) concentrations recorded for any marine mammal and these concentrations correlate to distance from a Superfund point‐source in the Turtle/Brunswick River Estuary (TBRE). Currently, little is known about the population structure of dolphins in this region. This study identifies and compares baseline data on abundance, habitat use, site‐fidelity, and ranging patterns of dolphins across two adjacent field sites; Brunswick, including the TBRE, and Sapelo, including the Sapelo Island National Estuarine Research Reserve. Sapelo is relatively undeveloped and was selected for comparison to the more contaminated TBRE. Dolphin densities increased with tributary size in both sites but dolphin density and total abundance were significantly higher in Sapelo than in Brunswick. Anthropogenic stressors within the TBRE may be an important factor contributing to the differences in abundance, density, and habitat use observed in this study.     

Spatial and temporal segregation of spawning habitat by catostomids in the Savannah River, Georgia and South Carolina, U.S.A.

Spawning aggregations of five species of catostomids were observed on the two mid-channel gravel bars of the Savannah River, Georgia and South Carolina, in 2004 and 2005 to assess the degree of spatial and temporal overlap in the use of this habitat and determine the habitat preferences leading to segregation. Spawning catostomids showed a considerable amount of temporal overlap in their use of these mid-channel gravel bars. The observed temporal overlap was consistent between 2004 and 2005 and corresponded to temperatures at which species were present. The distribution of catostomids was not uniform at the upstream gravel bar. Carpsuckers Carpiodes sp., spotted sucker Minytrema melanops and robust redhorse Moxostoma robustum both demonstrated some spatial overlap with notchlip redhorse Moxostoma collapsum ; however, their overall distributions were different from one another. Northern hogsucker Hypentelium nigricans was present across the gravel bars, apparently as an egg predator. Spawning catostomids segregated based on flow, depth, slope and substratum size. Whether due to limited habitat availability or changes in the timing of reproduction due to altered cues, temporal and spatial overlap occurs between spawning catostomids despite the apparent partitioning of available spawning habitat. It is unclear, however, if this overlap results in excessive mortality in the early life-history stages of these species. Results suggest spatial overlap among catostomid species was minimized due to species spawning in areas within a narrow range of conditions. Intraspecific interactions such as nest site superimposition or disturbance may be a concern.     

Population structure, reproduction and sex-change in a tropical East Atlantic grouper

Spawning time and sizes at first sexual maturity and at sex-reversal are described in the tropical blue-spotted grouper Cephalopholis taeniops . All juvenile fish possess non-functional ovaries. At sexual maturity, most juvenile fish become functional females. Some of these later change sex to become males. The remaining juvenile females change immediately to males, without time as functional females. This is a new scheme for sexual differentiation of groupers.     

Relative abundance of mosquito species (Diptera: Culicidae) on Big Pine Key, Florida, U.S.A.

Species diversity of mosquito (Diptera: Culicidae) collections in carbon dioxide-baited light traps was investigated on Big Pine Key, Florida, from 2000 - 2004. Twenty species of mosquitoes were collected during this study, the most commonly collected being Anopheles atropos, Culex bahamensis, Deinocerites cancer, and Ochlerotatus taeniorhynchus. Ochlerotatus taeniorhynchus is the dominant species at this location. For most of the mosquito species, more individuals were collected during the "high season" months (June to September) than in the "low season" months (January to March). During most years more mosquito species were collected in the high season than in the low season. Rank order of species collected was significantly correlated between low and high season. Species composition at this site appears to be relatively stable from year to year and from season to season.     

Influence of aquatic macrophyte habitat complexity on invertebrate abundance and richness in tropical lagoons

1. Aquatic plants are a key component of spatial heterogeneity in a waterscape, contributing to habitat complexity and helping determine diversity at various spatial scales. Theoretically, the more complex a habitat, the higher the number of species present. 2. Few empirical data are available to test the hypothesis that complexity increases diversity in aquatic communities (e.g. Jeffries, 1993 ). Fractal dimension has become widely applied in ecology as a tool to quantify the degree of complexity at different scales. 3. We investigated the hypothesis that complexity in vegetated habitat in two tropical lagoons mediates littoral invertebrate number of taxa (S) and density (N). Aquatic macrophyte habitat complexity was defined using a fractal dimension and a gradient of natural plant complexities. We also considered plant area, plant identity and, only for S, invertebrate density as additional explanatory variables. 4. Our results indicate that habitat complexity provided by the different architectures of aquatic plants, significantly affects both S and total N. However, number of individuals (as a result of passive sampling) also helps to account for S and, together with plant identity and area, contributes to the determination of N. We suggest that measurements of structural complexity, measured through fractal geometry, should be included in studies aimed at explaining attributes of attached invertebrates at small (e.g. plant or leaf) scales.     

Demersal fish assemblages associated with hard bottom habitat in the South Atlantic Bight of the U.S.A.

Synopsis Demersal fish communities associated with hard bottom habitats in the South Atlantic Bight were investigated in three depth zones (inner, middle and outer shelf) between 30° and 33°N latitudes. Fishes were sampled with trawls and baited fishing gear, and were observed by remotely operated underwater television. Most demersal hard bottom fishes demonstrated seasonal differences in abundance in each depth zone, especially at the inner and outer shelf stations. Diversity values from trawl catches were higher in winter than summer at inner and outer shelf stations, but lower in winter at middle shelf stations. Species richness was higher in summer than in winter at most stations, but H' diversity patterns were more influenced by community evenness. Diversity values were higher than those reported for similar depths in the Middle Atlantic Bight. Mean biomass of demersal teleosts for all stations combined was slightly greater in winter than in summer. There was no significant difference in biomass between stations in summer, however, middle shelf stations had significantly greater biomass than inner or outer shelf stations in winter. Biomass estimates from the hard bottom areas studied were considerably higher than those reported in the literature for sand bottom areas in the South Atlantic Bight, but less than those reported for tropical reefs. Cluster analysis revealed differences in community composition between day and night trawl tows at all stations, and greater seasonal differences in species composition at inner and outer shelf stations than at middle shelf depths. Underwater television provided useful complementary data to trawl catches, documented the presence of large fishes which avoided the trawl, and provided information on the community composition at high relief stations which could not be trawled.     

The influence of habitat on the size distribution of groupers in the upper Florida Keys

Synopsis The influence of habitat on the size distribution of groupers was examined at sites in the middle and upper Florida Keys. Transects were used to quantify the size distribution of groupers at study sites. There were significant differences in the size distribution of groupers within and among reef community types related to differences in species composition and patch reef size. Groupers with a giant life-history style (Sullivan & de Garine 1994) were more abundant, but smaller, on inshore patch reefs than offshore reef community types. However, grouper species with a dwarf life-history style (Sullivan & de Garine 1994) showed an opposite pattern with a lower abundance, but larger size, inshore than offshore. The length category of groupers constituting the majority of individuals observed on patch reefs was inversely related to reef size. Graysby Epinephelus cruentatus were shown to recruit to deeper (15–20 m), low-relief habitats offshore. Several factors influenced the size distribution of groupers in the study sites including habitat type, spear-fishing, competition, predation, and recruitment.     

生境破碎化过程对流域生境质量的影响

近几十年来,随着工业化、城市化的加速推进,人类活动对自然生境的干扰越来越频繁,导致生境破碎化与生境质量下降。在流域尺度上科学模拟生境破碎化过程及其对生境质量的影响,对于提升生物多样性和生态系统功能具有重要意义。以鄱阳湖流域为研究区域,基于InVEST模型分析区域生境质量的演变特征;从生境面积、生境边缘和生境隔离三个特征维度模拟生境破碎化过程;采用广义加性模型和地理探测器探究不同生境破碎化过程对生境质量变化的影响与交互作用。研究结果表明:(1)鄱阳湖流域生境质量呈下降趋势,从2000年的0.7862下降到2010年的0.7807,再下降到2020年的0.7715,但总体生境质量较好。生境质量较优的区域主要分布在流域南部、东北部以及西部地区,生境质量较差的区域主要分布在各个子流域的交界处。(2)2000-2010年,鄱阳湖流域生境面积占比下降、生境边缘增加和生境隔离增加三个生境破碎化过程分别占总研究区网格数的34.70%、30.15%和4.50%;2010-2020年分别占总研究区网格数的34.80%、30.69%和4.40%;2000-2020年分别占总研究区网格数的40.82%、37.50%和5.46%。生境面积减少的网格主要集中在鄱阳湖流域的中北部地区;生境边缘增加的网格分布和生境面积减少的网格分布相似;相比之下,生境隔离增加的网格较少,主要分布在各城市的中心城区范围。(3)生境破碎化过程对生境质量具有显著影响,两者呈非线性负相关关系;三个生境破碎化过程两两之间交互作用对生境质量的影响呈现双因子增强趋势。研究结果可为鄱阳湖流域生态格局优化与生境质量提升提供科学参考。     

Influence of within‐patch habitat quality on high‐Andean Polylepis bird abundance

Habitat restoration strategies for fragmented high Andean forest landscapes must consider the influence of within‐patch habitat quality on bird abundance. I examined vegetation and bird abundance at three locations within a highly fragmented Polylepis forest landscape in the Cordillera Vilcanota, southern Peru. Across the landscape, there was significant variation in the vegetation structure of Polylepis forest patches of different size categories, especially in terms of tree girth, tree height, tree density, and canopy vegetation structure. Principal Component Analysis extracted five factors of habitat quality, which together accounted for 74.2% of the variability within 15 habitat variables. Polylepis bird species differed in their responses to habitat quality but, overall, variation in Polylepis bird abundance was not fully captured by the range of habitat quality variables. Tall, dense vegetation cover was clearly important for 11 conservation‐important species, a high density of large trees was important for 10 species and primary forest ground cover was important for eight species. Habitat quality exhibited no significant influence on the abundance of only one species –Asthenes urubambensis. The abundance of seven species was associated with lower elevation forest, but only one species was associated with higher elevation forest. Management of habitat quality in large and medium remnant forest patches throughout the Cordillera Vilcanota, particularly in the 3800–4200 m elevation range, will be a cornerstone in ensuring the persistence of the majority of conservation‐important bird species populations.     

Linking fish trait responses to in‐stream habitat in reconstructed valley‐plugged stream reaches of the Coastal Plain,U.S.A.

Valley‐plug formation is a challenging consequence of stream channelization especially in physiographic regions with highly erodible soils. Upstream channel degradation and incision results in accelerated sediment delivery processes wherein downstream aggradation decreases stream power and creates sand‐clogged channels. Channel reconstruction is now meeting hydrogeomorphic goals related to valley‐plug remediation, yet there exists a need to understand how this practice also facilitates ecological restoration. We evaluated fish trait response to in‐stream habitat conditions in channelized, recently restored, and “least‐disturbed” reference reaches of Coastal Plain streams in West Tennessee. Restored reaches were ecologically similar to channelized reaches, having higher proportions of nest‐guarding omnivores that were correlated with higher percentages of pool habitats and lower wetted width:depth ratios compared to reference reaches. Reference reaches had higher proportions of fast‐water dwelling and specialized insectivores that were correlated with high abundance of large woody debris, high‐wetted width:depth ratios, and low percentages of pool habitats. We conclude that in‐stream habitats in reconstructed channels have yet to promote reach‐scale ecological restoration relative to fish assemblage organization because trait‐habitat associations were not similar to reference conditions. However, our results lend to the development of ecological restoration targets that can be incorporated in future channel reconstruction projects in valley‐plugged, channelized streams of the Coastal Plain.     

The association between meteorological variables and the abundance of Aedes taeniorhynchus in the Florida Keys

The black salt marsh mosquito, Aedes taeniorhynchus, is a serious nuisance pest and a potential vector of a number of arboviruses. This study examined the effect of wind direction, wind speed, temperature, and time of year on the abundance of Ae. taeniorhynchus collected in CO₂‐baited light traps at 12 sites in the Florida Keys during 2004. The dependent variable analyzed was the natural log of weekly mosquito abundance. The previous week's wind speed and wind direction, and the current week's temperature were used as independent variables. Simple and multiple linear regression models were used to assess the significance and nature of association between the meteorological variables and the natural log of mosquito abundance, and to determine whether the meteorological variables had significant associations with mosquito abundance after also controlling for time of year. Week of year was treated as a circular independent variable in the regression models, using the sine and cosine of week in radians to model the periodic seasonal fluctuation in mosquito abundance. Mosquito abundance was significantly associated with all meteorological variables and with week of year. Individually, previous week's wind speed and wind direction, and current week's temperature were able to explain respectively 24.5%, 24.5%, and 52.1% of the variation in mosquito abundance observed over the year. Week of year had the strongest individual association with mosquito abundance, explaining 65.7% of the variation in mosquito abundance. The meteorological variables were still significantly associated with mosquito abundance, after controlling for week of year. Week and the meteorological variables together explained 79.2% of the variation in mosquito abundance. The regression models fit to the data from this study suggest a strong periodic seasonal variation in mosquito abundance, with meteorological conditions explaining a significant portion of the variation beyond the seasonal trend.     

Habitat alteration and its effects on native fishes in the upper Tennessee River system, east-central U.S.A.

The upper Tennessee River drainage, which includes portions of the States of Virginia, North Carolina, and Tennessee, supports an exceptionally diverse fish fauna. Recent reductions in abundance and geographic ranges of several freshwater fishes have promulgated the imposition of protective measures for about 115 species among the three states, with nearly half of those species occurring in the upper Tennessee River. Most protected species are darters (Percidae: Etheostomatinae) or minnows (Cyprinidae), and are typically small, benthic invertivores. Major impacts on the fish fauna have resulted from dams, introduced species, toxic spills, mining and agriculture. An important cumulative effect of these impacts is fragmentation of the watershed; nearly 40% of the riverine habitat in major tributaries is either impounded or altered by tailwater discharges. The isolation and stress imposed on tributaries of the river have caused and will continue to cause extirpations of fishes, mussels and other aquatic fauna. Numerous federal, state, and private organizations are co-operating in efforts to protect rare species and habitats, improve agricultural and coal-producing practices, and enforce regulations for industrial and municipal effluents.     

Decline of some west-central Florida anuran populations in response to habitat degradation

Recent reports have suggested that a global decline in amphibian populations has taken place during the past few decades. Urban development is thought to affect the richness and abundances of species and, therefore, could be an important cause of decline. We estimated the richness and abundances of anurans in wetlands at a residential development and in similar wetlands at a nearby undeveloped park. The residential development originally was pine flatwoods habitat, as is the undeveloped park curiently. We also compared the anuran species' composition of the park in 1992 with the composition in 1974.Both richness and abundances of anurans in the residential development were different than those in the undeveloped park. Employing the same amount of sampling effort at both sites, we trapped or observed 11 species at the developement and 15 species at the park, and trapped 569 individuals at the development and 1224 individuals at the park. The anuran species richness at the undeveloped park in 1992 was nearly the same as in 1974; a single rare species apparently was not present in 1992. Of the 15 species present in both surveys, 14 showed higher abundances in 1992 than in 1974.We suggest that the current differences between the residential development and the park have resulted from degradation of both the uplands used by many species during the dry season and the temporary wetlands used by many species for reproduction. Four species especially sensitive to such degradation, Bufo quercicus, Scaphiopus h. holbrookii, Hyla femoralis, and H. gratiosa, were the species missing from the residential development.Not all species of anurans typical of pine flatwoods appeared to be affected adversely by development. Three species of ranids, Rana utricularia, R. grylio, and R. catesbeiana, were found in higher abundances at the residential development than at the park. These ranid species breed in a wide variety of aquatic systems, including the permanent bodies of water that are now abundant in the development, and probably use the uplands less than other anurans.If amphibian decline is international in scope, then the decline could be attributable either to global changes caused by humans, or to local, but widespread, environmental degradation, or to a combination of factors. While much recent popular focus has been on potential global causes of decline, we believe that this emphasis may have caused attention to be taken away from local causes that, as our study demonstrated, may be at least as important. We suggest that in many places, local environmental degradation is insidiously chipping away at amphibian diversity, and that more emphasis should be placed on these local causes than is now the case.