The following biological components concerning the population dynamics of Atlantic menhaden (Brevoortia tyrannus) were investigated: growth, natural mortality, migration, fishing mortality, and recruitment. We found that a hypothesis of density-dependent growth is strongly supported by the data and that the dependence of growth on abundance appears to occur prior to recruitment. Age-specific natural mortality estimates seem biologically reasonable, except the estimate for age 1 menhaden, which appears to be too low. Most of the estimated migration probabilities also seem to be biologically reasonable, especially during the summer season for age 2 fish. Estimated age-specific fishing mortality rates demonstrate the increased fishing pressure on age 3 and younger fish since the early 1960's. When the environmental variables (temperature and Ekman transport) are excluded from the spawner–recruit analysis, then the Beverton–Holt model fits as well as other models examined, and it is the only model that is significant at the 0.05 probability level. Of the environmental variables examined, only westward Ekman transport in the South Atlantic region shows a relationship with recruitment. The unnormalized gamma function, which includes the Ricker model as a special case, is more responsive to the inclusion of westward Ekman transport than the Beverton–Holt model.

A model including an age-structure, a stochastic egg-recruitment relationship, density-dependent juvenile growth, age-dependent fishing mortality, and fecundity dependent upon size as well as age was used to investigate three types of harvesting strategies: constant yearly catch policies, constant fishing mortality rate policies, and "egg escapement" policies, which are defined in the article. Because of stochastic recruitment, constant yearly catch policies appear unsuitable for managing Atlantic menhaden (Brevoortia tyrannus). Both other types of policies are suitable, but the egg escapement policies have higher long-term average catches. Using decision theory, we investigated risks due to the randomness of recruitment and to the estimation errors for the biographical parameters in our model. The risks appear to be acceptable.

Instruction in colposcopic technique is now an integral component of residency training in obstetrics and gynecology. No statistical method for assessing colposcopy skills has been reported on before. The statistical calculations of sensitivity, specificity and kappa were applied to determine if there was any progressive acquisition of colposcopy skills by the colposcopy trainee during the four-year residency program.

SUMMARY Stochastic approximation is a sequential technique which can be used for optimizing the mean of a random variable y(x) in terms of a parameter vector x, when the mean is unknown but y(x) can be observed for any value of x. This paper is intended to introduce and illustrate stochastic approximation to those statisticians unfamiliar with the technique. The Atlantic menhaden is a commercially important fish in the herring family (Clupeidae). Stochastic approximation is used in conjunction with a stochastic simulation model of the menhaden population to determine optimal values for the two parameters in a proposed class of menhaden harvesting policies. The objective is to maximize the expected utility of the random catch over a 25-year period. Optimization is a response-surface problem. Although some of the more familiar sequential response-surface methods might have been successfully applied, the nonsequential response-surface techniques would have been too expensive for estimation of a specific feature of the surface, such as the location of the maximum. The results of using stochastic approximation are encouraging. Atlantic menhaden are migratory fish caught from Florida to New England mainly by purse-seining. Menhaden are not palatable to humans, but they are processed into two important products, fish oil and fish meal. The oil is used in the manufacture of paints, lubricants, and cosmetics, and the meal is a high-protein ingredient in animal feed. Together, Atlantic and Gulf menhaden support the largest U.S. commercial fishery measured in pounds landed, and, excluding shellfish, menhaden catches rank next to those of tuna and salmon in monetary value. At present the Atlantic menhaden fishery is subjected to some intrastate regulation, but it is not managed on a fishery-wide basis. Catches of menhaden experienced a rapid decline after 1962 and have only partially recovered, but some biologists feel that proper management could increase future catches substantially. To explore the

Colposcopically directed cervical biopsies performed by experienced colposcopists have greatly reduced the need for conization of the cervix to evaluate patients with cervical intraepithelial neoplasia (CIN). Because of the subjectivity of the colposcopic technique and variable time required to become skilled, continued reliance on cervical conization is often recommended to validate colposcopic findings for novice colposcopists . We assessed the colposcopic skill of residents in training in obstetrics and gynecology who had received 9-12 months of instruction in colposcopic techniques. Biopsies of each quadrant of the ectocervix were done after the resident recorded his or her colposcopic diagnosis. In 26% of the patients there was overestimation or underestimation of the histologic findings by more than one grade in the cervical quadrant suspected on colposcopy to contain the most advanced CIN lesion. In 30% of patients the histologically most advanced CIN lesion was not identified by the colposcopist . In 11% of patients with histologic findings of CIN both cytology and colposcopy were negative. Only 69% of the histologically confirmed lesions were diagnosed colposcopically by the resident colposcopists . The four-quadrant, colposcopically directed biospy technique is recommended as an effective training method for the beginning colposcopist .