Evaluation of a Leased Oyster Bottom in Mississippi Sound

Twenty-four pairs of spat plates, strategically located on a 600-ha (1500-a) oyster lease, were monitored biweekly to determine the rate of oyster spatfall. Spatfall occurred from May 6 to July 31 and again from August 15 to October 24, 1979. The greatest spatfall occurred from August 15 to September 4, 1979. Data from shell bags that accompanied the spat plates indicated a maximum growth of 3.2 cm in two months. Oyster spat which attached to the planted cultch materials on the leases grew up to 7.9 cm during the 17-month sampling period, ending December 11, 1979. The lease area is capable of producing commercial-sized oysters in two seasons

The Production of Triploid Oyster Larvae (Crassostrea Virginica (Gmelin)) in Louisiana.

Gonadal recycling of oyster broodstock, salinity effects during induction, and cytochalasin B (CB) dosage were investigated as factors affecting the production of triploid oyster larvae in Louisiana. These factors were studied at an oyster hatchery on Grand Isle, LA during 1992-1994 to help transfer triploid oyster technology to the Gulf region. Oyster broodstock were held nearshore in Caminada Bay, Louisiana and histologically analyzed between induced spawnings and during the winter of 1992-1993. Gametogenesis was analyzed qualitatively by developmental staging and quantitatively using mean gonad/body ratios (GBR) per section. The monthly percent occurrence of the developmental stages, as well as histological evidence, showed that gonadal recycling was occurring. Significantly different mean GBR\u27s were found between developmental stages and between successful and unsuccessful spawning attempts (P $\u3c$ 0.05). Experiments were conducted by exposing fertilized oyster eggs to 10 ppt, 20 ppt and 30 ppt seawater after a one week broodstock acclimation period at 13 ppt, 20 ppt and 30 ppt. Resulting polar body extrusion data revealed significant differences between mean synchrony levels of broodstock salinity\sp{\*}treatment salinity interactions at mean development time (P $\u3c$ 0.00138). The rates of change in synchrony at each interaction were also plotted. Both analyses showed the highest levels and rates of synchrony were at broodstock salinity\sp{\*}treatment salinity interactions of 20$\vert$30 ppt, 20$\vert$20 ppt and 30$\vert$30 ppt. Low salinity was detrimental to obtaining synchronous meiotic development. Survival and ploidy of D-stage oyster larvae were estimated after exposing embryos to CB dosages of 0.5 mg/L, 0.25 mg/L, and 0.125 mg/L for 10-15 minutes, with 0.05% DMSO and ambient seawater as controls. No significant differences were found in survival and triploidy between CB dosages of 0.5 mg/L and 0.25 mg/L and between 0.125 mg/L and the controls (P $\u3c$ 0.05). Recommendations are provided to optimize triploid induction of Crassostrea virginica using CB

Health, Children, and Elderly Living Arrangements: A Multiperiod-Multinomial Probit Model with Unobserved Heterogeneity and Autocorrelated Errors

This paper develops a general multiperiod-multinomial probit model for panel data to estimate the living arrangements of the elderly. The model has the following features: (a) In each period choices do not necessarily obey the assumption of independence of irrelevant alternatives. (b) Unobserved person-specific attributes are treated as random effects. These random effects may also be correlated across alternatives. (c) In addition, unobserved choice-specific utility components may persist over some time, creating an autoregressive and/or heteroscedastic error structure. The model is estimated by simulating the choice probabilities in the likelihood function. We examine several variants of the specification of the correlation structure and investigate the extent the biases created by ignoring intertemporal correlations.

The Provision of Time to the Elderly by Their Children

This paper uses matched data on the elderly and their children to study the provision of time by children to the elderly. It develops a Tobit model as well as a structural model to analyze the determinants of this decision. The main determinants of the amount of time given to parents appear to be the parent's age, reported health, and institutionalization status, and the children's age, health, and sex. Older parents, less healthy parents, and non-institutionalized parents receive more time from their children, while younger children, healthier children, and female children provide more time. In contrast to these demographic determinants, economic variables, such as children's wage rate and income levels, appear to play a rather insignificant role in the provision of time. In addition, the evidence does not support the hypothesis that parents purchase time from their children.

Enhancing Seed Availability For the Hard Clam (Mercenaria mercenaria) Aquaculture Industry By Applying Remote Setting Techniques

The goal of this study was to test a technology that may help ensure a reliable and consistent supply of high quality and inexpensive clam seed to growers, thus fostering an emerging aquaculture industry by eliminating a seed shortage that limits sustainability. The overall objectives were to develop, test and demonstrate technical procedures and determine the financial feasibility of transferring remote setting technology from the Pacific Northwest molluscan shellfish industry to the hard clam aquaculture industry in Florida. (PDF has 44 pages.

Estimating the Cost of Executive Stock Options: Evidence from Switzerland

It is often argued that Black-Scholes (1973) values overstate the subjective NEWLINE value of stock options granted to risk-averse and under-diversified executives. NEWLINE We construct a “representative” Swiss executive and extend the certainty- NEWLINE equivalence approach presented by Hall and Murphy (2002) to assess NEWLINE the value-cost wedge of executive stock options. Even with low coefficients NEWLINE of relative risk aversion, the discount can be above 50% compared to the NEWLINE Black-Scholes values. Regression analysis reveals that the equilibrium level NEWLINE of executive compensation is explained by economic determinant variables NEWLINE such as firm size and growth opportunities, whereas the managers’ pay-forperformance NEWLINE sensitivity remains largely unexplained. Firms with larger NEWLINE boards of directors pay higher wages, indicating potentially unresolved NEWLINE agency conflicts. We reject the hypothesis that cross-sectional differences in NEWLINE the amount of executive pay vanish when risk-adjusted values are used as NEWLINE the dependent variable