The Extent of Seasonally Suitable Habitats May Limit Forage Fish Production in a Temperate Estuary

The sustained production of sufficient forage is critical to advancing ecosystem-based management, yet factors that affect local abundances and habitat conditions necessary to support aggregate forage production remain largely unexplored. We quantified suitable habitat in the Chesapeake Bay and its tidal tributaries for four key forage fishes: juvenile spotted hake Urophycis regia, juvenile spot Leiostomus xanthurus, juvenile weakfish Cynoscion regalis, and bay anchovy Anchoa mitchilli. We used information from monthly fisheries surveys from 2000 to 2016 coupled with hindcasts from a spatially interpolated model of dissolved oxygen and a 3-D hydrodynamic model of the Chesapeake Bay to identify influential covariates and construct habitat suitability models for each species. Suitable habitat conditions resulted from a complex interplay between water quality and geophysical properties of the environment and varied among species. Habitat suitability indices ranging between 0 (poor) and 1 (superior) were used to estimate seasonal and annual extents of suitable habitats. Seasonal variations in suitable habitat extents in Chesapeake Bay, which were more pronounced than annual variations during 2000–2016, reflected the phenology of estuarine use by these species. Areas near shorelines served as suitable habitats in spring for juvenile spot and in summer for juvenile weakfish, indicating the importance of these shallow areas for production. Tributaries were more suitable for bay anchovy in spring than during other seasons. The relative baywide abundances of juvenile spot and bay anchovy were significantly related to the extent of suitable habitats in summer and winter, respectively, indicating that Chesapeake Bay habitats may be limiting for these species. In contrast, the relative baywide abundances of juvenile weakfish and juvenile spotted hake varied independently of the spatial extent of suitable habitats. In an ecosystem-based approach, areas that persistently provide suitable conditions for forage species such as shoreline and tributary habitats may be targeted for protection or restoration, thereby promoting sufficient production of forage for predators. Further, quantitative habitat targets or spatial thresholds may be developed for habitat-limited species using estimates of the minimum habitat area required to produce a desired abundance or biomass; such targets or thresholds may serve as spatial reference points for management.

Spatial ecology and growth in early life stages of bay anchovy Anchoa mitchilli in Chesapeake Bay (USA)

The bay anchovy Anchoa mitchilli is the most abundant fish in Chesapeake Bay (USA) and is a vital link between plankton and piscivores within the trophic structure of this large estuarine ecosystem. Baywide distributions and abundances of bay anchovy eggs and larvae, and larval growth, were analyzed in a 5 yr program to evaluate temporal and spatial variability based on research surveys in the 1995-1999 spawning seasons. Effects of environmental variability and abundance of zooplankton that serve as prey for larval bay anchovy were analyzed. In the years of these surveys, 97.6% of eggs and 98.8% of larvae occurred in the polyhaline lower bay. Median egg and larval abundances differed more than 10-fold for surveys conducted in the 5 yr and were highest in the lower bay. Within years, median larval abundance (ind. m-2) in the lower bay was generally 1-2 orders of magnitude higher than upper-bay abundance. Salinity, temperature, and dissolved oxygen explained 12% of the spatial and temporal variability in egg abundances and accounted for 27% of the variability in larval abundances. The mean, baywide growth rate for larvae over the 5 yr period was 0.75 ± 0.01 mm d-1, and was best explained by zooplankton concentration and feeding incidence. Among years, mean growth rates ranged from 0.68 (in 1999) to 0.81 (in 1998) mm d-1 and were fastest in the upper bay. We identified environmental factors, especially salinity, that contributed to broadscale variability in egg and larval production.

PENGARUH JENIS ASAM ALAMI TERHADAP PENURUNAN KADAR LOGAM BERAT TIMBAL DALAM DAGING IKAN TERI (Stelophorus indicus Sp) ASAL TELUK PALU

Research on the effect of type natural acid against decline of content heavy metals plumbum in meat anchovy (Stelophorus indicus Sp) origin bay Palu. The purpose of this study was to determine the best type of acid used in dissolving levels of plumbum as heavy metals for 1 hour immersion and to determine the number of levels of heavy metals of lead that can be dissolved during immersion 1 hour. This study begins with a sample digestion using nitric acid, further qualitative test reagents dithizon 0.005% (positive), potassium iodide (positive) and sodium carbonate (postitif). Qualitative results test that showed a positive result then measured in metal content of plumbum using atomic absorption spectrophotometer (AAS) at λ 283.3 nm. Then soaking using tamarind are 5%, acetic acid 10%, the filtrate pineapple 100%, starfruit 100% and lime 25% for 1 hour at room temperature, after measuring the metal content of plumbum with atomic absorption spectrophotometer (AAS) in λ 283.3. The results show levels of heavy metals plumbum before immersion average of 0.8 mg/kg, the average concentration of heavy metals plumbum after soaking tamarind 5% amounting to 0.787 mg/kg (1.64%), 10% acetic acid at 0.789 mg/kg (1.39%), pineapple filtrate 100% of 0.7882 mg/kg (1.49%), starfruit 100% 0.789 mg/kg (1.39%) and lime 25% of 0.7916 mg/kg (1.06%). Thus tamarind 5% is the best type of acid to reduce levels of plumbum metal in Palu bay anchovy origin.Keywords: Acid, Anchovy (Stelophorus indicus Sp), Content, Plumbum

İzmir Körfezi (Orta Ege Denizi)’ndeki Hamsi Engraulis encrasicolus (Linnaeus, 1758) Yumurta ve Larvalarının Bolluk ve Dağılımı

In this study, the abundance and distribution of anchovy Engraulis encrasicolus (Linnaeus, 1758) eggs and larvae in İzmir Bay were examined in 2013. For this aim, seasonally obtained the plankton samples from 11 stations identified in the bay. Anchovy eggs and larvae were obtained all seasons except winter. As a result, total 6889 eggs/m², 3231 larvae/m² were obtained. The minimum and maximum diameters of anchovy eggs; in short exis 0.49 to 0.56 mm (average 0.51±0.43), in long axist 1.09 to 1.30 mm (average 1.21±0.006). Minimum and maximum larvae length is 2.28-9.8 mm.

Examination of an Estuarine Fish Assemblage Over an Inshore Artificial Reef

The perceived value of oyster reefs as fish habitat has led to many restoration projects in areas of historically high oyster populations. This study evaluated fish usage of a limestone cobble mimic oyster reef in Barataria Bay, Louisiana, as compared to a mud-bottom reference site. Emphasis was given to species of economic and ecological importance, including spotted seatrout (Cynoscion nebulosus), Atlantic croaker (Micropogonias undulatus), and bay anchovy (Anchoa mitchilli). There were no observed differences in community structure or catch per unit effort (CPUE) between habitats, likely due to high variability in the data, though seasonal differences were observed. CPUE of spotted seatrout, Atlantic croaker, and bay anchovy did not differ between habitats. Seasonal differences in abundance were detected, with significantly higher CPUE of spotted seatrout in summer, of Atlantic croaker in spring and summer, and of bay anchovy in winter. Spotted seatrout and Atlantic croaker were both significantly larger over the artificial reef, while bay anchovy were significantly larger over the mud bottom. Spotted seatrout, a prized recreational fishing species in Louisiana, appeared to be the only species that showed higher biomass, determined by numbers and size, at the the artificial reef. This is important in the context of managing habitat enhancement projects. While the reef did not increase numbers or species richness of the overall fish community, it did have an effect on one recreationally important species. Therefore, the success of such projects is based as much on the intended purpose, as its affect on the overall community.