Assessment of estuarine habitats for resident and estuarine-dependent species: tools for conservation and management

My research in coastal Ecuador and the northern Gulf of Mexico (GOM) elucidated differences in value of shallow estuarine habitats for fishes and invertebrates. I focused on mangrove and tidal river habitats in Ecuador, and oyster reef, vegetated marsh edge, and nonvegetated bottom habitats in the GOM. Coastal Ecuador has lost 20-30% of mangrove wetlands over the past 30 years. Such habitat loss can impair the ecological functions of wetlands. In this study I identified the fish community of the remaining mangrove wetland in Rio Palmar, Ecuador. For comparison, an adjacent tidal river without mangroves, Rio Javita, was also sampled. I found that although Rios Palmar and Javita are characterized by relatively low fish-species richness compared to other tropical estuarine systems, they appear to provide important habitat for several economically- and ecologically-valued species. In the GOM, I examined the fish and invertebrate communities of adjacent oyster reef (oyster), vegetated marsh edge (VME), and nonvegetated bottom (NVB) habitats. Three main relationships emerged: 1) Oyster and VME provide habitat for significantly more species (as a measure of richness) relative to NVB; 2) Oyster and VME provide habitat for uncommon and rare species; and 3) Many of the species collected in multiple habitats occurred at higher abundances in oyster or VME habitat. Contrary to the current low value ranking of oyster habitat relative to other estuarine and salt marsh habitats, oyster provides high quality habitat for many species. Understanding how key species utilize estuarine habitats is critical for future conservation and management efforts. My research indicated that VME habitat may provide better foraging options for juvenile pinfish (Lagodon rhomboides), and together with corroborating evidence from other studies, suggest that VME provides a critical nursery function for juvenile pinfish, especially in estuaries where seagrass habitat is sparse or nonexistent. Additionally, I documented that juvenile white shrimp (Litopenaeus setiferus) select for oyster habitat because of higher food availability and not because of refuge needs from predation by blue crabs. Oyster habitat appears to provide a nursery function for juvenile white shrimp. Overall, my research demonstrated that structurally complex habitats, such as mangroves, VME, and oyster provide essential habitat at the community, population, and individual levels

Replicated shape variation between simple and complex habitats in two estuarine fishes

A replicated pattern of habitat-associated morphology among different lineages may represent adaptive convergence. Deviation from the replicated (shared) pattern of diversification reflects unique (e.g. species specific) effects resulting from site- or species-specific selection, intrinsic factors (e.g. G matrix differences) or chance historical events (e.g. genetic drift). For two distantly-related estuarine fishes [Lagodon rhomboides (Sparidae; Linnaeus) and Leiostomus xanthurus (Sciaenidae; Lacepede)], we examined shared and unique instances of body shape variation between seagrass (complex) and sand (simple) microhabitats at four sites. We found extensive shape variation between microhabitats for both species. As a shared response, both species from sand had subterminal snouts and long caudal peduncles, whereas those from seagrass had terminal snouts and deep bodies. Unique responses involved a greater difference in Lagodon rhomboides head shape between microhabitats compared to L. xanthurus. Patterns of shape variation fit ecomorphological predictions for foraging in the respective microhabitats (simple versus complex) because deep bodies are expected for fish that must negotiate complex habitats and subterminal snouts facilitate benthic foraging common in barren habitats. Parallel differentiation between microhabitats simultaneously suggests that individuals of each species use a particular microhabitat within estuaries for development and the differentiation in shape represents adaptive convergence. Spatial variation in the magnitude of shape differences between microhabitats was an unexpected finding and suggests that phenotypic variation operates at multiple scales within estuaries

Morphological Diversity of the Cynoscion Group (Perciformes: Sciaenidae) in the Gulf of Guayaquil Region, Ecuador: A Comparative Approach

We assess morphological diversity of species of the Cynoscion group in the Gulf of Guayaquil (GOG) using traditional morphometric methods. Five species from the GOG assemblage (C. albus, C. analis, C. phoxocephalus, C. squamipinnis, and Isopisthus remifer) are compared to four species from a relatively well-studied assemblage in the western Atlantic (C. arenarius, C. nebulosus, C. nothus, and C. regalis). The two regional species assemblages broadly overlap in morphology, but sympatric species segregate relatively well within each assemblage. The GOG species segregate primarily along the major axis of shape variation in the study, which is associated with variation in the anal, second dorsal, and caudal fins. The western Atlantic species segregate primarily along the second major axis of shape variation, which is most strongly associated with variation in gill raker length, and less strongly with pectoral fin length, eye diameter, and length of the third dorsal spine. Patterns of morphological divergence among the western Atlantic species support the hypothesis that morphological divergence is associated with ecological divergence. Comparisons across assemblages indicate that morphological divergence among species in the GOG is substantial. Consequently, Cynoscion species in the GOG may be highly divergent in ecological habits, which would have important management implications, but further ecological research is needed. This study provides a first glimpse into the major patterns of morphological diversification in the Cynoscion group

Age, Growth, and Reproduction in Two Coastal Populations of Longnose Gars

<p>Measurements of age, growth, and reproduction are excellent tools for determining the ecological role and impact of a species within an ecosystem. Longnose Gar <i>Lepisosteus osseus</i> is a large, ubiquitous top predator in fresh and saline waters of the eastern United States. Even though the species is common, their basic biology has been largely uncharacterized in brackish and marine waters. Specimens were collected from two estuaries: Winyah Bay and Charleston Harbor, South Carolina, from May 2012 through July 2013 to examine age, growth, and reproduction in tidally influenced systems. This species is fairly long-lived, with maximum ages of 17 and 25 years for males and females, respectively. The von Bertalanffy growth model yielded significantly higher growth rates for males than for females. Reproductive histology and the gonadosomatic index indicated that Longnose Gars exhibit determinate fecundity and spawn in late spring following a long development period during fall and winter. These life history parameters provide valuable insight into the basic biology of Longnose Gars and into how they function in estuarine environments. Further research on the precise timing and location of spawning movement, as well as daily movement patterns of this species, would provide a more comprehensive knowledge of Longnose Gar reproductive biology.</p> <p>Received May 18, 2015; accepted October 9, 2015</p

Ocurrencia de Sphoeroides rosenblatti Bussing, 1996 (Teleostei: Tetraodontidae) en la costa de la provincia de Guayas, Ecuador, y una comparación con Sphoeroides annulatus (Jenyns, 1842) (Nota científica en Inglés)

Se recolectaron trece ejemplares juveniles de Sphoeroides rosenblatti Bussing, 1996 en un bosque pequeño y fuertemente impactado de mangle situado en Palmar, provincia de Guayas, Ecuador. Esta especie era conocida previamente solo de aguas costeras de Costa Rica y Panamá. Se contrastó la ocurrencia y morfología de S. rosenblatti con ejemplares de Sphoeroides annulatus (Jenyns, 1842) recolectadosen la misma área. La presencia de S. rosenblatti no estuvo significativamente asociada con la temperatura del agua, salinidad, o morfología del río, mas hubo evidencia de segregación espacial entre S. rosenblatti y S. annulatus. También encontramos pequeñas pero significativas diferencias entre las características morfométricas de estas especies, que estuvieron en acuerdo con la descripción original basada en especimenes centroamericanos. Utilizando todas las características morfométricas, se realizó un análisis de función discriminante que produjo un vector capaz de clasificar correctamente a todos los ejemplares. Se reporta una ampliación importante de la distribución conocida de S. rosenblatti y se agrega una especie nueva a la ictiofauna de la costa continental del Ecuador

Factors Influencing Refuge Occupation by Stone Crab \u3ci\u3eMenippe adina\u3c/i\u3e Juveniles in Mississippi Sound

A greater understanding of population dynamics is essential in the management of any species. The Western Gulf stone crab, Menippe adina, is taken as incidental by-catch in the blue crab, Callinectes sapidus, fishery in Mississippi. However, there is a lack of information on the ecology of M. adina in estuaries of the northern Gulf of Mexico. We know that M. adina is associated with hard-bottom habitats such as rock-rubble jetties and oyster reefs and that this habitat is sparse in Mississippi Sound, which mainly consists of soft-bottom habitat. Many studies have demonstrated that habitat complexity is important to several benthic crustaceans because it provides a matrix of different sized refuges that organisms can use to escape from predation. The importance and availability of refugia varies throughout the life history of organisms because of the increase in size of an organism as it grows. Refuge limitation acting on a specific size class may create a demographic bottleneck thereby limiting the production of a population through mortality, migration, or stunting of the affected size class. We tested this refuge limitation bottleneck hypothesis in juvenile stone crabs by supplementing an existing oyster reef with four different sizes of polyvinyl chloride (PVC) pipe. We found that lack of refuge affected both population size structure and density of large juvenile stone crabs on the reef. We also found that competition for available refuges may occur among M. adina and two other xanthid crab species, Eurypanopeus depressus and Panopeus simpsoni. We examined the diet of oyster toadfish, Opsanus beta, in Mississippi Sound and found that the three xanthid crabs comprised a significantly large portion of oyster toadfish diet. Predation by O. beta emphasized the importance of the availability of suitable refugia for the xanthids

Ocurrencia de Sphoeroides rosenblatti Bussing, 1996 (Teleostei: Tetraodontidae) en la costa de la provincia de Guayas, Ecuador, y una comparación con Sphoeroides annulatus (Jenyns, 1842) (Nota científica en Inglés)

Se recolectaron trece ejemplares juveniles de Sphoeroides rosenblatti Bussing, 1996 en un bosque pequeño y fuertemente impactado de mangle situado en Palmar, provincia de Guayas, Ecuador. Esta especie era conocida previamente solo de aguas costeras de Costa Rica y Panamá. Se contrastó la ocurrencia y morfología de S. rosenblatti con ejemplares de Sphoeroides annulatus (Jenyns, 1842) recolectadosen la misma área. La presencia de S. rosenblatti no estuvo significativamente asociada con la temperatura del agua, salinidad, o morfología del río, mas hubo evidencia de segregación espacial entre S. rosenblatti y S. annulatus. También encontramos pequeñas pero significativas diferencias entre las características morfométricas de estas especies, que estuvieron en acuerdo con la descripción original basada en especimenes centroamericanos. Utilizando todas las características morfométricas, se realizó un análisis de función discriminante que produjo un vector capaz de clasificar correctamente a todos los ejemplares. Se reporta una ampliación importante de la distribución conocida de S. rosenblatti y se agrega una especie nueva a la ictiofauna de la costa continental del Ecuador

Replicated shape variation between simple and complex habitats in two estuarine fishes

A replicated pattern of habitat-associated morphology among different lineages may represent adaptive convergence. Deviation from the replicated (shared) pattern of diversification reflects unique (e.g. species specific) effects resulting from site- or species-specific selection, intrinsic factors (e.g. G matrix differences) or chance historical events (e.g. genetic drift). For two distantly-related estuarine fishes [Lagodon rhomboides (Sparidae; Linnaeus) and Leiostomus xanthurus (Sciaenidae; Lacepede)], we examined shared and unique instances of body shape variation between seagrass (complex) and sand (simple) microhabitats at four sites. We found extensive shape variation between microhabitats for both species. As a shared response, both species from sand had subterminal snouts and long caudal peduncles, whereas those from seagrass had terminal snouts and deep bodies. Unique responses involved a greater difference in Lagodon rhomboides head shape between microhabitats compared to L. xanthurus. Patterns of shape variation fit ecomorphological predictions for foraging in the respective microhabitats (simple versus complex) because deep bodies are expected for fish that must negotiate complex habitats and subterminal snouts facilitate benthic foraging common in barren habitats. Parallel differentiation between microhabitats simultaneously suggests that individuals of each species use a particular microhabitat within estuaries for development and the differentiation in shape represents adaptive convergence. Spatial variation in the magnitude of shape differences between microhabitats was an unexpected finding and suggests that phenotypic variation operates at multiple scales within estuaries