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SUMMARY. Between 1967 and 1977, catches of Tilapia galilaea in Lake Kinneret fell from an annual average of about 200 tonnes to a low of 70 tonnes in 1974, and then returned to their former level. Total yearly mortality (Z) was estimated at 1.84 between 1970 and 1976. Assuming a natural mortality (M) of 0.94, total stock size averaged 300–700 tonnes in that period, while recruitment averaged < 0.7–3 million per year. Three broods hatched in years of relatively high water levels (1970, 1971 and 1972) yielded especially low recruitment. The Von Bertalanffy growth coefficient (K) was estimated at 0.67, and final length (L∞) at 25–36cm total length. First year's growth, 23–152mm, was closely related to final length, which appeared to be affected by genetic variation in the population. Yearly fluctuations in size distribution were attributed to changes in the proportions of fast- and slow-growers, as well as in the abundance of year-classes. Recruitment to the fishery, at 17–20cm, occurred between ages l+and3+. The highest growth rates for age-1 T, galilaea, 1–2% mean weight per day, occurred in April and May, the Peridinium season. However, only a small proportion of age-1 fish reached marketable size by July, when their food supply began to diminish. During the autumn months, there was hardly any length increment, and all T. galilaea became lean, especially the age-0 group. It is surmised that recruitment of stocked fish could be increased by introduction in December and by use of fingerlings which are potentially able to grow to marketable size in less than two seasons.

Data validity is as critical an issue for practice as it is for research. This Research Note is a brief account of an effort to subject family functioning data to a validity analysis by using multiple informants. Results indicate that knowledge about variations in degree of validity by subject areas canenhance the quality of data for use in professional practice.

A detailed study of the salivary gland chromosomes of Simulium tuberosum in Southern Ontario revealed four well-defined breeding units and a likely fifth, all sympatric. Except for "floating" inversions, the banding sequence differs between siblings only on the sex-determining arm, 2S. Of the seven basic arrangements of this arm, three are found in more than one breeding group, i.e. they bridge the siblings.Inversion analysis of the entire complement uncovered 83 "floating" rearrangements, generally of low frequency, and produced data on chromosomal linkage, specificity, and breakpoint concentration. Most interestingly, seven of the more widely distributed and functionally important inversions were found to be shared between two or three of the siblings.The occurrence of bridging sequences of 2S and shared "floating" inversions attests to the close genetic affinity of the four sympatric forms and is suggestive of occasional hybridization.

Background One of the more common behavioral manifestations of dementia-related disorders is severe problems with out-of-home mobility. Various efforts have been attempted to attain a better understanding of mobility behavior, but most studies are based on institutionalized patients and the assessment usually relies on reports of caregivers and institutional staff, using observational approaches, activity monitoring, or behavioral checklists. The current manuscript describes the research protocol of a project that measures mobility in Alzheimer's disease and related cognitive disorders in an innovative way, by taking advantage of advanced tracking technologies. Methods/design Participants are 360 demented persons, mildly cognitively impaired persons, and unimpaired controls aged ≥ 65 in Israel and Germany. Data regarding space-time activities will be collected via a GPS tracking kit for a period of 4 weeks in 3 waves (one year apart) with the same participants (using a repeated measures design). Participants will be interviewed by use of a battery of instruments prior to and following GPS data collection. Further, a family member will complete a questionnaire both before and after data tracking. Statistical analyses will strive to explain differences in mobility based on a wide range of socio-structural, clinical, affect-related and environmental variables. We will also assess the impact of the use of advanced tracking technology on the quality of life of dementia patients and care givers, as well as its potential as a diagnostic tool. Systematic assessment of ethical issues involved in the use of tracking technology will be an integral component of the project. Discussion This project will be able to make a substantial contribution to basic as well as applied and clinical aspects in the area of mobility and cognitive impairment research. The innovative technologies applied in this study will allow for assessing a range of dimensions of out-of-home mobility, and provide better quality data.