Effects of Biotic and Abiotic Factors on Growth and Relative Survival of Young American Shad, Alosa sapidissima, in the Connecticut River

1985 ◽  
Vol 42 (10) ◽  
pp. 1640-1648 ◽  
Author(s):  
Victor A. Crecco ◽  
Thomas F. Savoy
Keyword(s):  
Growth Rates ◽  
Abiotic Factors ◽  
Survival Rates ◽  
Relative Survival ◽  
American Shad ◽  
Zooplankton Abundance ◽  
Connecticut River ◽  
River Flows ◽  
Alosa Sapidissima ◽  
Specific Growth Rates

We examined the hypothesis that temporal oscillations in zooplankton abundance, river flows, and temperatures in the Connecticut River affect the survival and growth rates of larval and juvenile American shad, Alosa sapidissima, among 5-d cohorts. The relative survival rates between newly hatched shad larvae and juveniles were low among early cohorts (May 21 – June 15), but rose rapidly among later cohorts (June 21 – July 6) when river flows were low and temperatures and zooplankton densities were high. Age of larval and juvenile shad was estimated by counting daily rings on sagittal otoliths and age-specific length increments determined by backcalculation techniques. Cohort-specific growth rates of larval shad increased linearly with rising zooplankton densities, and asymptotically with rising river temperatures and declining flows. By contrast, juvenile growth rates among 5-d cohorts showed no significant linear or nonlinear relationships to water temperatures and flows.

Effects of Fluctuations in Hydrographic Conditions on Year-Class Strength of American Shad (Alosa sapidissima) in the Connecticut River

1984 ◽  
Vol 41 (8) ◽  
pp. 1216-1223 ◽  
Author(s):  
Victor A. Crecco ◽  
Thomas F. Savoy
Keyword(s):  
Environmental Variables ◽  
River Flow ◽  
Abiotic Factors ◽  
American Shad ◽  
Larval Feeding ◽  
Monthly Precipitation ◽  
Connecticut River ◽  
Alosa Sapidissima ◽  
Hydrographic Conditions ◽  
Class Strength

We evaluated a parent–progeny relationship for Connecticut River shad, Alosa sapidissima, with population data from 1966 through 1982. The hypothesis that shad year-class strength is established during larval development mainly by abiotic factors was assessed by correlation analysis between environmental variables, year-class strength, weekly zooplankton densities, hydrographic conditions, and larval feeding success among the 1979 through 1982 year-classes. No significant parent–progeny relationship was found for American shad even after recruitment variations due to river flow and water temperatures were removed. All three environmental variables (mean river discharge, water temperatures, and total monthly precipitation) were significantly correlated with shad year-class strength for the month of June, the period when most American shad larvae emerge.

Daily Mortality Rates of Larval and Juvenile American Shad (Alosa sapidissima) in the Connecticut River with Changes in Year-Class Strength

1983 ◽  
Vol 40 (10) ◽  
pp. 1719-1728 ◽  
Author(s):  
V. Crecco ◽  
T. Savoy ◽  
L. Gunn
Keyword(s):  
Survival Rates ◽  
Mortality Rates ◽  
American Shad ◽  
Connecticut River ◽  
Alosa Sapidissima ◽  
Growth And Survival ◽  
Juvenile Mortality ◽  
First Feeding ◽  
Gompertz Equation ◽  
Class Strength

Age-specific growth and survival rates were estimated for larval and juvenile American shad (Alosa sapidissima) from the Connecticut River from 1979 to 1982. Relative indices (CPE) of year-class strength of juveniles determined from seine sampling in 1978–82 and 1966–73 are compared with resulting levels of adult recruitment. Length–age data for larval and juvenile American shad were determined from sagittal otoliths. Length increments among larval and juvenile shad followed an asymptotic pattern with age, both life stages being well described by the Gompertz equation. Larval survivorship curves from 1979 to 1982 were age specific, with mortality rates of 19.8–25.6%/d for first feeding larvae and 4.3–8.7%/d for larvae approaching metamorphosis. By contrast, juvenile mortality rates were much lower (1.8–2.0%/d) and more consistent among years. Juvenile indices of year-class strength from 1966 to 1973 were positively correlated (r = +0.92, df 7, P < 0.001) with recruitment levels of adult females 4–6 yr later, suggesting that year-class strength of shad is established prior to the juvenile stage.

Effects of turbidity on prey consumption and growth in brook trout and implications for bioenergetics modeling

2001 ◽  
Vol 58 (2) ◽  
pp. 386-393 ◽  
Author(s):  
John A Sweka ◽  
Kyle J Hartman
Keyword(s):  
Growth Rates ◽  
Brook Trout ◽  
Specific Growth ◽  
Abiotic Factors ◽  
Foraging Strategies ◽  
Turbid Water ◽  
Daily Consumption ◽  
Consumption Rates ◽  
The Difference ◽  
Specific Growth Rates

Brook trout (Salvelinus fontinalis) were held in an artificial stream to observe the influence of turbidity on mean daily consumption and specific growth rates. Treatment turbidity levels ranged from clear (<3.0 nephelometric turbidity units (NTU)) to very turbid water (> 40 NTU). Observed mean daily specific consumption rates were standardized to the mean weight of all brook trout tested. Turbidity had no significant effect on mean daily consumption, but specific growth rates decreased significantly as turbidity increased. Brook trout in turbid water became more active and switched foraging strategies from drift feeding to active searching. This switch was energetically costly and resulted in lower specific growth rates in turbid water as compared with clear water. Bioenergetics simulations were run to compare observed growth with that predicted by the model. Observed growth values fell below those predicted by the model and the difference increased as turbidity increased. Abiotic factors, such as turbidity, which bring about changes in the activity rates of fish, can have implications for the accuracy of predicted growth by bioenergetics models.

Food Availability and Consumption by Young Connecticut River Shad Alosa sapidissima

1972 ◽  
Vol 29 (10) ◽  
pp. 1495-1499 ◽  
Author(s):  
Raymond C. Levesque ◽  
Roger J. Reed
Keyword(s):  
Stomach Content ◽  
Food Habits ◽  
Negative Selection ◽  
Content Volume ◽  
American Shad ◽  
Initial Time ◽  
Connecticut River ◽  
Alosa Sapidissima ◽  
Selection For ◽  
Selection Of

Food habits of young American shad (Alosa sapidissima) were studied in the Connecticut River above Holyoke, Massachusetts, 1969. Diurnal feeding data revealed a peak in stomach content volume at 8:00 PM during midsummer. Larval shad fed mainly on aquatic crustaceans and tendipedid larvae and pupae. Juveniles ingested the most abundant organisms: crustaceans, tendipedid larvae and pupae, hydropsychid larvae and adult insects. Electivity data indicated positive selection for tendipedid pupae and crustaceans and negative selection for hydropsychid larvae and tendipedid larvae. Selection of Trichoptera larvae by young shad in significant amounts was documented for the initial time.

Behavior of Adult American Shad (Alosa sapidissima) Homing to the Connecticut River from Long Island Sound

1973 ◽  
Vol 30 (12) ◽  
pp. 1847-1860 ◽  
Author(s):  
Julian J. Dodson ◽  
William C. Leggett
Keyword(s):  
Tidal Current ◽  
Open Water ◽  
American Shad ◽  
Behavior Patterns ◽  
Connecticut River ◽  
Directed Movement ◽  
Alosa Sapidissima ◽  
Preferred Direction ◽  
Tidal Current Velocity ◽  
Ultrasonic Tracking

The migratory behavior of American shad (Alosa sapidissima) approaching their natal river during the final saltwater stage of the spawning migration was studied using ultrasonic tracking and conventional tagging procedures. Initial displacement of most sonic-tagged shad released without displacement adjacent to and 10 km west of the Connecticut River was not in the direction of the home river. These fish, however, homed successfully to the Connecticut River as did dart-tagged shad released in the same areas.Shad exhibited two major behavior patterns; countercurrent orientation in response to the reversing tidal current and adjustment of swimming speed to changes in tidal velocity. Countercurrent orientation was equally significant during daylight and darkness, whereas the adjustment of swimming speeds to tidal current velocity was more significant during daylight than darkness.Shad tracked to the west exhibited a westerly bias inherent in the basic open water behavior patterns. Shad exhibited a greater degree of directed movement when oriented against the ebb tide and adjusted their swimming speeds to exceed the ebb tide velocity and to approximately equal the flood tide velocity. Shad tracked to the east exhibited the same major behavior patterns but with the opposite directional bias.A hypothesis is presented suggesting that the location of the home river is achieved by means of a nonrandom search. Environmental clues indicative of the Connecticut River act to establish a preferred direction of displacement while the actual unidirectional displacement is achieved by reference to the rate and direction of tidal currents.

Comparison of Logistic Regression and Discriminant Analyses for Stock Identification of Anadromous Fish, with Application to Striped Bass (Morone saxatilis) and American Shad (Alosa sapidissima)

1990 ◽  
Vol 47 (8) ◽  
pp. 1570-1577 ◽  
Author(s):  
Michael H. Prager ◽  
Mary C. Fabrizio
Keyword(s):  
Logistic Regression ◽  
Striped Bass ◽  
Logistic Model ◽  
Morone Saxatilis ◽  
Hudson River ◽  
American Shad ◽  
Stock Identification ◽  
Connecticut River ◽  
Alosa Sapidissima ◽  
Discriminant Analyses

We examined the applicability of logistic regression to stock identification studies and compared its performance on two data sets to that of linear and quadratic discriminant functions. Logistic regression can be used to model a categorical dependent variable associated with continuous or discrete independent variables, and is preferred to discriminant analyses when the explanatory variables are not multivariate normal. Our examples were American shad (Alosa sapidissima) from the Connecticut River and Hudson River estuaries, and striped bass (Morone Saxatilis) from the Hudson River, Chesapeake Bay, and Roanoke River estuaries. In the examples we used a resampling method to assess classification and allocation errors of the two methods on new data. For the shad data, the logistic model classified significantly more fish correctly, and provided a significantly better estimate of stock composition. For the striped bass data, the two methods classified about the same proportion of fish correctly, but the logistic model gave a significantly better estimate of stock composition.

scholarly journals Study of growth and productions of tilapia (Oreochromis niloticus) on different population densities in monoculture

2020 ◽  
Vol 9 (2) ◽  
pp. 76-83
Author(s):  
F Sharmin ◽  
MS Rahman ◽  
M Shahjahan ◽  
P Chowdhury
Keyword(s):  
Population Density ◽  
Growth Rates ◽  
Oreochromis Niloticus ◽  
Specific Growth ◽  
Survival Rates ◽  
Fish Population ◽  
Fish Production ◽  
Population Densities ◽  
Specific Growth Rates ◽  
Supplementary Feed

The experiment was conducted to determine the effects of population densities of tilapia (Oreochromis niloticus) on the growth and production of tilapia in monoculture system. Fish population density was 80 fish per decimal under treatment-I, 160 fish per decimal under treatment-II and 320 fish per decimal under treatment-III. In the ponds under three treatments supplementary feed was not used. The average initial length and weight of the fry of tilapia was 4.48 cm and 0.067 g, respectively. The ponds were fertilized fortnightly with urea and TSP at the rates of 60 g, and 90 g per decimal, respectively. Mean survival rates of fish under treatment-I, treatment-II and treatment-III were 91.12%, 82.82% and 66.23%, respectively. The specific growth rates (SGR, % per day) of fish under treatment-I, treatment-II and treatment-III were 5.49%, 4.95% and 4.61%, respectively. The calculated net fish production of the ponds under treatment-I was 2.65 ton ha-1 yr-1 and that of the ponds under treatment-II was 2.55 ton ha-1 yr-1 and that of the ponds under treatment-III was 2.68 ton ha-1 yr-1. The net fish production under treatment-I and treatment-III were 2.65 ton ha-1 yr-1 and 2.68 ton ha-1 yr-1 higher than that of treatment-II, taking net fish production under treatment-I for 100%. According to survival rates and specific growth rates treatment-I is the best. So, the population density of 80 fish per decimal (under treatment-I) might be considered the best among the three treatments. Int. J. Agril. Res. Innov. Tech. 9(2): 76-83, December 2019

Net Avoidance Behavior in American Shad (Alosa sapidissima) as Observed by Ultrasonic Tracking Techniques

1971 ◽  
Vol 28 (8) ◽  
pp. 1167-1171 ◽  
Author(s):  
William C. Leggett ◽  
Robert A. Jones
Keyword(s):  
Lateral Line ◽  
Avoidance Behavior ◽  
Visual Detection ◽  
American Shad ◽  
Connecticut River ◽  
Alosa Sapidissima ◽  
Light Intensities ◽  
Ultrasonic Tracking ◽  
Ultrasonic Transmitters

During tracking of 13 adult American shad (Alosa sapidissima) with ultrasonic transmitters in 49 approaches to commercial drift gillnets in the lower Connecticut River, only one shad was captured. Typically, shad moved to within 1–2 m of the net before sensing its presence, then turned and swam along the net, close to the mesh, to its end, where they turned and continued their upriver migration. Sight appeared to play an important role in net detection. However, 14 avoidances were observed when light intensities were inadequate to allow visual detection of the mesh. It was concluded that other senses, perhaps the lateral line, also function in net avoidance, especially when sight is impaired.

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