Northern Quahog (=Hard Clam) Mercenaria Mercenaria Age At Length Relationships And Growth Patterns In The York River, Virginia 1954 To 1970

Northern quahogs Mercenaria mercenaria were grown in trays suspended in the York River, Virginia from November 1954 (4 months old) to December 1970 (16 years old). Measurements of shell length (mm) were made at least once a year from 1954 to 1970 and measurements of shell width (mm) were made in November 1962 and August 1965 and then once per year from 1967 through 1970. Quahog densities within the trays ranged from 1500 m(-2) (November 1954 to October 1955) to 269 m(-2) (November 1955 to December 1970). Quahog shell length (mm) increased with age (yr) and was described with a Von Bertalanffy growth model (coefficient of determination = 0.93). Most of the growth in shell length occurred in the first 6 years with clams reaching shell lengths of 58 mm by November 1960 and maximum shell lengths of 77-84 mm by 1963 (age 9). Shell length:shell width relationships were similar for tray held and wild quahogs collected from the York River during 1967 to 1970. The observed annual shell length growth increment decreased exponentially with quahog age. Standardized shell length growth index (SGI) values for I I of the 15 years for which data are available describe better than expected quahog growth trends although there was no clear relationship between SGI and average annual surface temperature or average growth period (water temperature \u3e 7 degrees C, typically March to November) surface temperature in the York River between 1955 and 1967

Observations On The Early Life History And Growth Rates Of Juvenile Channel Whelks Busycotypus Canaliculatus (Linnaeus, 1758)

Channel whelks (Busycotypus canaliculatus) were cultured from hatch through 171 days to describe the early life history and growth rates of juveniles. Whelks began to hatch at water temperatures of 15-18 degrees C. Channel whelks grew quickly from average shell lengths (SL) at hatch of 3.8 mm (SE = 0.1) to an average of 48.4 mm SL (SE = 1.3, n = 42 individuals) at 171 days post-hatch. The largest individual reached 53.2 mm SL, a gain of similar to 49.4 mm SL in 171 days, with a growth rate of 0.29 mm/day. Juvenile whelks readily consumed oyster (Crassostrea virginica) and mussel (Geukensia demissa) prey. A linear growth model (SL = 0.21 x [Age (days post-hatch)] + 1.6068) was used to describe the channel whelk age-at-length relationship. This is the first published growth curve for juvenile channel whelks. The observed juvenile growth rates for B. canaliculatus (0.21 mm/day) are higher than those previously described for Busycon carica. Whelk mortality was very low (\u3c2%) after whelks reached SLs of similar to 10-12 mm

Comparison Of Growth Rates Between Diploid DEBY Eastern Oysters (Crassostrea Virginica, Gmelin 1791), Triploid Eastern Oysters, And Triploid Suminoe Oysters (C. Ariakensis, Fugita 1913)

Oyster size and morphology affect individual oyster physiology, reproductive biology, and habitat production as well as population ecological services and availability for commercial harvest. Options for oyster restoration and fishery facilitation for eastern oyster (Crassostrea virginica) populations in the Chesapeake Bay include the use of disease resistant diploid eastern oysters (DEBY strain), triploid eastern oysters, and triploid Suminoe oysters (Crassostrea ariakensis) with the objective of providing a marketable product in a reasonable time frame. Shell height-at-age, growth in shell height in relation to environmental conditions, ontogenetic changes in morphology, and changes in biomass for groups of triploid Suminoe, triploid eastern, and diploid DEBY eastern oysters held at identical grow out conditions for the first two years of their lives were evaluated. Triploid Suminoe oysters reached shell heights of 76 mm (market size in Virginia of 3 in) at 1.1 y with triploid eastern oysters and diploid DEBY oysters attaining the same size at 1.2 y and 1.5 y, respectively. Increases in shell height were positively correlated with water temperature and salinity with the largest increases in shell height typically occurring in warmer months. Holding density significantly affected ratios of shell height (SH) to shell width (SW) and SH to shell inflation (SI) for all three oyster populations. Oysters at lower densities showed a decrease in SH:SI ratio indicative of increased cupping as well as a reduction in SH:SW indicating a trend toward more discoid or rounded form. Tissue dry weight (g) and ash free dry tissue weight (g) increased nonlinearly with size within each population and were statistically different across the three populations examined. Triploid Suminoe oysters had higher tissue weights than either triploid or diploid DEBY eastern oysters of similar ages. Both triploid eastern and Suminoe oysters had higher tissue weights than diploid DEBY oysters of similar age. Observed differences in growth rates and morphology between these groups of oysters affect both the ecological services they provide (filtration rates as well as habitat) as well as their fishery potential (time to market size)

Ecological interactions between benthic oyster reef fishes and oysters

Restoration of oyster reef structures rehabilitates habitats and the multi-level ecological communities built on eastern oysters (Crassostrea virginica), the keystone species. Quantitative descriptions of ecological interactions within a habitat are required to delineate essential fish habitats for management and protection. Parallel development of primary (oysters) and secondary trophic levels (benthic fishes) offer an ecological metric of restoration progress over time. The interaction between larval oysters and larval fishes (e.g., Gobiosoma bosc, Chasmodes bosquianus) is quantitatively examined. Oyster settlement estimates for Palace Bar reef, Piankatank River, Virginia are of the same order of magnitude as field densities of recently settled oysters. Benthic fish settlement estimates are within an order of magnitude of observed adult densities. Zooplankton community composition around the reef is temporally variable and plankton densities range from 10 2--106 animals per m3 across temporal scales. Nocturnal densities of naked goby and striped blenny larvae around Palace Bar reef were 3 to 4 orders of magnitude higher than densities observed during daylight hours. Diurnal changes in larval fish abundance near Palace Bar reef are related to ambient light intensities and diurnal vertical migration by prey species. Naked goby, striped blenny, and feather blenny (Hypsoblennius hentzi) larvae selectively consumed bivalve veligers, in multi-factorial laboratory feeding experiments. Temporal co-occurrence of larval oysters and larval fishes was not observed in 1996 field collections although historic oyster settlement data strongly support the probability of co-occurrence during most years. Two different methods are used to estimate the larval oyster - larval fish interaction in the absence of field data. Given existing oyster and fish demographics on Palace Bar reef, larval fishes have the capacity to drastically reduce, perhaps eliminate, local veliger populations if they co-occur. The strength of this interaction is directly related to oyster demography-fecundity relationships. In the absence of veligers, larval fishes consume other plankton taxa that are abundant around the reef. Naked gobies and striped blennies are generalists. Oyster reefs provide optimal rather than essential habitat. Reef restoration will facilitate development of related ecological communities by providing optimal habitat conditions for these ubiquitous estuarine species

Pre-juvenile Naked Goby (Gobiosoma bosc) age and growth

Due to the abundance of larval naked gobies, Gobiosoma bosc, within the estuarine ichthyoplankton, it is important to understand their age and growth. Naked gobies are a largely distributed, both geographically and within an estuary, small, benthic fish species. There are 3 pairs of otoliths, calcium carbonate structures within the ear canal, that detect vibrations and record the age of the fish, both daily and annually. Using laboratory-reared gobies of a known age (Tremont et al. 2015), daily signatures on the sagittal otoliths were first validated to be daily, then a growth curve for the wild caught larvae was calculated as well as estimated spawning dates. Wild fish were collected from Clambank Creek in North Inlet estuary during the spawning seasons in 2018 and 2019. Sub-daily signatures were evident between daily signatures in, in most otoliths, for the cultured and wild fish, but no regular pattern was determined. After daily deposition was confirmed within the cultured fish, wild caught gobies from 2018 and 2019 were then aged and a two parameter exponential regression growth curve was calculated to estimate growth for both year classes individually and together. Cultured larvae showed no relationship between the known days post hatch and the total otolith growth signatures observed, but daily deposition was validated by the relationship between known age and observed daily signatures. Predicted hatch lengths for wild larvae were 2.49 ± 0.26 mm with an instantaneous daily growth rate of 0.043 ± 0.004 mm d-1. Hatch sizes in wild fish larvae were significantly smaller than those observed in the cultured larvae (3.1 ± 0.2 mm). Nest hatching dates were predicted from wild larval fish ages to establish a baseline for spawning times for these important ichthyoplankton

Observations On The Biology Of The Veined Rapa Whelk, Rapana Venosa (Valenciennes, 1846) In The Chesapeake Bay

The recent discovery of the Veined Rapa whelk (Rapana venosa, Valenciennes, 1846) in the lower Chesapeake Bay provides an opportunity to observe the initial biological and ecological consequences of a novel bioinvasion. These large predatory gastropods occur in subtidal, hard bottom habitats in the lower Bay and are capable of feeding, mating, and moving while completely burrowed. Hard clams (Mercenaria mercenaria) are consumed preferentially in the laboratory when offered concurrently with oysters (Crassostrea virginica), soft clams (Mya arenaria), and mussels (Mytilus edulis). Chesapeake Bay R. venosa readily open and consume large hard clams (30 to 85 mm SH) leaving no visible signs of either drilling or boring behavior. Shell morphology and thickness may provide an inherent size-selective predation refuge for Rapa whelks in the Bay. These same shell characteristics may change the dynamics of shell selection by local hermit crabs, particularly the striped hermit crab, Clibanarius vittatus. Recent collections of striped hermit crabs from the Hampton Roads area indicate that very large striped hermit crabs are using empty Rapana shells as shelters

Continuing trophic studies on constructed “restored” oyster reefs

AMASS choreographed by Eloy Barragán. Color is removed from the low sidelight, creating a natural warmth highlighting the individual dancers as if floating in space.https://ir.uiowa.edu/lighting_design/1189/thumbnail.jp

Habitat Disturbance Combined With Life History Traits Facilitate Establishment Of Rapana Venosa In The Chesapeake Bay

The veined rapa whelk (Rapana renosa) invasion of the Chesapeake Bay in the United States was first observed in 1998. Chesapeake Bay rapa whelk population demographics, age-at-length relationships, and invasion progression (temporal, spatial) from 1998 to 2009 are described. Between June 1998 and November 2009, 27,624 rapa whelks, ranging from 11- to 195 mm shell length (SL), were collected from the lower Bay. Using a Von Bertalanffy age-at-length model (R-2=0.99), the 195-mm SL whelk collected in 2007 was 26 y old, making 1981 the estimated year of first introduction. Age-frequency distributions for Ocean View, Hampton Bar, and the lower James River showed increased whelk numbers per age class and consistent representation of Age 2-3 through Age 7-8 whelks throughout the time series indicating recruitment and establishment. Whelk range expansion into James River oyster habitats began in 2004 and continued through 2009. Whelks occupy shallow areas during warmer months, move into deeper habitats during cooler months, and annually reinvade shallow areas as temperatures warm seasonally. Channels act as salinity refugia and conduits between foraging habitats. Salinity tolerances allow rapa whelk use of epifau.nal habitats bounded by the 10-12 isohalines formerly used by native oyster drills [Urosalpinx cinerea (Say, 1822); Eupleura caudata (Say. 1822)] as juveniles and infaunal habitats with salinities of 15-25 that do not overlap with native whelks (Busycotypus canailculatus, liusycon carica) as adults. Establishment was facilitated by local disturbance of native species distributions by Tropical Storm Agnes (1972)