96-hour TL50 values of unbleached kraft mill effluent (UKME) for Neornysis arnericana were found to range from concentrations of 3.29 to 6.85% at 26-28 C and 3.90 to 7.30% at 16-18 C. Differences between batches of effluent proved insignificant in experiments at each temperature regime. Furthermore, UKME did not lose its toxicity, when stored for 5 to 7 days at 4 C. A concentration of 20% effluent killed 100% of the organisms in 8 of the 12 bioassays. Slope functions and confidence limits of TL50 were calculated. This dissertation is from the Joint Program Degree from the College of William & Mary and University of Virginia and awarded by the University of Virginia.

A 3n factorial design to evaluate the effects of an abrupt introduction of striped bass, Morone saxatilis from a closed-system rearing facility into a variety of experimental temperature and salinity combinations has demonstrated a considerable hardiness of juvenile fish. Striped bass less than two months old had over 80.0%, survival during seven days subsequent to acute introduction from an average ambient condition of 21.0 ± 3 C at 0.20 to 4.8% into temperatures of 18 C and 24 C and salinities of 4.0% and 12.0%. Relative growth in these treatments was significantly greater than in the 12 C treatment at all salinities . These results lend a degree of flexibility to the stocking program as to site selection and time of release, both of which should be governed by food types and quantities available, and the concentration and activity of predators. This dissertation is from the Joint Program Degree from the College of William & Mary and University of Virginia and awarded by the University of Virginia.

The commercial seabass notting fishery and the trawl fishery in the Blackfish Bank area east of the entrance to Chincoteague Bay were used to study the biology of the rock crab, Cancer irroratus Say. Highest relative abundance of rock crabs occured in February, March, and April when coldest inshore (<30m) bottom water temperatures occurred. Relative abundance during all other months was extremely low. The apparent seasonal change in relative abundance may be due to an inshore-offshore seasonal migration of mature crabs following the seasonal inshore-offshore shift of colder bottom water. Male rock crabs grow to a significantly larger size than females. The carapace width range of males captured in the potting fishery was 66 to 141 mm; and 25 to 106 mm for females. In the trawl fishery the width range for males was 20 to 137 mm; and 22 to 102 mm for females. In both pot and trawl catches the male to female ratio was biased in favor of males. Males comprised 92% of the pot catch and 84% of all crabs captured by trawl. From August through December all crabs were in the hard shell intermolt stage. Small percentages of soft crabs occurred from January through June. Papershell crabs predominated in February, March and April. It is probable that most crabs molted in January and the process of exoskeleton hardening took several months. Ovigerous females were captured in seabass pots in April and June and in trawls from February through April. All ovigerous crabs were in hard shell condition. Gondal inspection of males and the presence of eggs on females indicated that rock crabs mature at a relatively small size (30 mm carapace width). Female rock crabs have a deeper body and wider abdomen than equivalent width males. Abdomen width grows more rapidly for females after the onset of sexual maturity than before. Mature females have a longer carapace than equivalent width males. Male and female regressions of chela length on carapace width could not be compared statistically but plots of the equations suggest no sexual difference. This dissertation is from the Joint Program Degree from the College of William & Mary and University of Virginia and awarded by the University of Virginia.

Bibliography: pages 94-99. / The primary aim of this study was to assess the rate of recovery of macrobenthic communities after offshore marine mining. Three techniques, namely univariate, distributional and multivariate, were used to make this assessment. Two distinct areas, the northern and southern research areas, were investigated, and statistical and numerical analyses were conducted for each area independently. Data were aggregated to, and analysed at, the genus level. Replicates were arranged in temporal categories according to recent mining history. The northern research area appears to be affected by mining activity in terms of species composition, but not species diversity. Statistical testing detected significant differences between unmined replicates and all other temporal categories for this area, and this was also discernible in the cluster analysis and ordination plots. The overall picture generated suggests that the northern research area is affected immediately and severely by mining activity, resulting in rapid changes in species composition. However, the period of 15-19 months subsequent to mining is insufficient to allow the community to recover to a stable state. The southern research area, on the other hand, shows a slightly different scenario, with mining activity having a severe and immediate impact on both species composition as well as species diversity. Recently mined sites were found to be significantly different from both unmined sites and sites mined 43-51 months ago. The latter two categories were not found to be significantly different from each other. The results suggest that the road to recovery in the southern research area is a slow, but steady one in terms of species composition. This was particularly apparent in the results of the "SIMPER" analysis where the level of similarity between temporal categories increased steadily with time after mining. The overall picture suggests that the area has recovered substantially after 43-51 months, and that the community approximates that of the unmined area with regard to species composition. Geological analyses were also conducted, with results indicating a prevalence of fine surficial sediment particles in unmined sites, and coarse surficial sediment particles in recently mined sites. Percentage gravel, in particular, was found to be a reliable indicator of the condition of a site with regard to the level of disturbance. Altered stratigraphy and changes in particle size distribution as a result of mining activity are considered to have a noticeable effect on the structure of benthic communities. A number of taxa were found to be particularly reliable as indicator species. In both the northern and southern research areas, polychaetes (specifically Prionospio pinnata and the Lumbrineris genus) were abundant in unmined sites as well as in sites mined 43-51 months ago in the southern research area. Individuals of the genus Nassarius, on the other hand, were scarce in unmined sites, but abundant in recently mined sites. These taxa appear to be reliable indicators of the level of recovery attained in previously mined areas.

Summary in English. / Bibliography: p. [199]-210. / The primary aim of the study was to assess the status and productivity of chokka squid. Main hypotheses examined are the following: that the sharp decline in the trawl fishery catch per unit effort (CPUE) data in the early 1980s, reflects a real decline in the trawlers catch rate; that the decline in the trawl CPUE index is caused by the jig fishery removing the biomass that otherwise would be available to the trawl fishery; that the jig fishery "disturbs" the spawning process and causes a decline in subsequent recruitment. Catch and effort data from the two fisheries, as well as biomass estimates from spring and autumn research surveys, were used. The two main fisheries and the catch and effort data are described. General Linear Modelling (GLM) was performed on the CPUE data from the trawl fishery in order to obtain annual indices of abundance. Further, results from a GLM analysis on two years of monthly jig CPUE data are presented. The dynamics of the stock biomass on the spawning grounds were modelled in order to assess the effects of current levels of effort and the existing closed season on the resource. The dynamics of the stock and the fishery were captured by a simple biomass-based model. Two dynamic methods were used to estimate model parameters: 1. a process-error estimator; 2. an observation-error estimator. All model parameter were estimated by maximum likelihood, and the corresponding confidence intervals were estimated by bootstrapping.

Although the phytoplankton of the waters off the west coast of South Africa (the Benguela Current region) has been the subject of several detailed studies in the past, data on that of the S.W. Indian Ocean has been almost entirely restricted to incidental references in the reports of expeditions which have passed through the area. Consequently, little has been known of the species composition and distribution of the phytoplankton, and nothing of its seasonal fluctuations. This study was designed to provide a broad picture of the phytoplankton of the area, the primary objective being a critical determination of the species composition. The material was collected by the S.A.S. Natal on four seasonal cruises in the area as a contribution to the International Indian Ocean Expeditions. A net-sampling technique was used to provide the maximum amount of material for quantitative analysis. The phytoplankton was found to be extremely rich in variety, 402 taxa being identified from the 98 samples collected. Of these 233 were diatom taxa, 157 dinoflagellate taxa, and the remainder being composed of members of the Chrysophyeeae (coccolithophorids), Cyanophyceae and Xanthophyceae. These are listed in the systematic section together with original references and other references used by the author for their identification. The local and general distributions or the taxa are described and many of the taxa are illustrated by line drawings or microphotographs. 5 new species are described, as well as 1 new variety, and it was found necessary to provide new names for several species. Full systematic details are given for all new or rare taxa.

During the summer of 1978-79 diatoms dominated the communities from October to January but microflagellates were dominant in February and March. Low concentrations of ATP, chlorophyll a protein and carbohydrate were measured in Type 1 water with protein/carbohydrate ratios being )1. In Type 2 water concentrations of chlorophyll a ATP and protein were high and the protein/carbohydrate ratio was)l. Concentrations of chlorophyll a and ATP remained high in Type 3 water but the protein/carbohydrate ratio decreased to <1 due to an increase in the concentration of acid-soluble glucan. It was concluded that the communities were in an active phase of growth in Type 1 and Type 2 water when adequate nutrients were available, but were in a slow-growing phase in Type 3 water when nitrate concentrations were low.

Closed seasons are generally implemented on the presumption that they increase reproductive output of fished populations. This is based on the assumption that the imposition of a closed season during the breeding season allows more individuals to reproduce, as they are not being harvested. I evaluated the validity of imposing closed seasons during the breeding season by creating a simulation model using the limpet Cymbula granatina as a test case and then compared the fol lowing four scenarios: 1) an unharvested population; 2) no closed season imposed; 3) a closed season imposed during the breeding season; and 4) a closed season imposed outside the breeding season, to determine the effects of the latter three situations on the reproductive output and yield. It was determined that closed seasons do not significantly affect the reproductive output of the population and that the timing of closed seasons made no difference to the reproductive output of the population, as the output was the same for populations with closed seasons during the breeding season or outside the breeding season. Survivors, catch in numbers and yield in biomass were affected by the timing of closed seasons, with higher outputs for each obtained when the closed season was closer to the month when individuals become of harvestable size. It was thus concluded that the imposition of a closed season at any time of the year is an effective management measure if imposing the closed season can reduce annual fishing mortality, but the imposition of a closed season specifically during the breeding season with a view to increase reproductive output brings no benefits relative to closure at any other time of the year. Moreover, any closure will be ineffective if it does not also bring about a reduction of annual fishing mortality. The reasons for advocating closure of a fishery during the breeding season are thus based on false grounds in the case of the limpet C. granatina.

Kelp is widely used as feed in the abalone aquaculture industry in South Africa, and farmers have reported different feed quality between the two dominant kelp species occurring along the west and southwest coasts with Ecklonia maxima reported as having a better Food Conversion Ratio (FCR) than Laminaria pallida. Total protein content and other nutritional components (Carbon, Nitrogen and moisture content) of two kelp species, E. maxima and L. pallida were investigated. The kelps were collected from Kommetjie (borderline of west and southwest coasts). Seasonal total protein content of E.maxima from a commercially-harvested kelp bed in Jacobsbaai (west coast) was compared with crude protein levels (measured as %N x 6.25). Total protein was extracted and quantified using the Bradford method. No significant difference in carbon content was found between seasons for E. maxima but there was a significant difference in average carbon content between E. maxima (30.79 %) and L. pallida (27.79 %). No seasonal pattern was observed in the nitrogen content, and hence crude protein content, of E. maxima (seasonal crude protein averaged 7.8% of dry weight) and there was no significant difference found between E. maxima and L. pallida (crude protein averaged 9. 05% of dry weight). There was no significant seasonal difference in total protein (averaged 0.99% of dry weight) and no significance found between species. The reported better FCR in abalone feed comprised of E. maxima rather than L.pallida, if correct, is likely to be related to higher carbohydrate content (measured here as carbon) and not to higher protein content. E. maxima differs from L. pallida with regards to carbon storage, but not protein content

The subtidal seaweed communities of the KwaZulu-Natal coast are poorly understood. A recent collaborative research project between Belgian and South African phycologists, however, is currently investigating the diversity and biogeographical affinities of the marine benthic algal flora of this region. The newest leg of the project is focusing on correlating biogeographic patterns with abiotic factors in the area between the St. Lucia estuary and Sodwana Bay, where it has become evident that there is a huge turnover in species composition. The present study examines seaweed community change along a depth gradient (1-30 m depth) at Sodwana Bay on the KwaZulu-Natal (KZN) coast, South Africa. All seaweed cover within 25 x 25 cm quadrats was collected, identified and weighed. The environmental variables, depth and % sand cover, were also measured. Both biomass and presence/absence data were ordinated to show community differentiation related to the environmental variables. The seaweed communities are largely red turfs, with a total of 82 Rhodophyte, 14 Chlorophyte, and 8 Phaeophyte taxa recorded. These turf communities showed exceptional diversity with 105 taxa (&gt;25 % of recorded KZN flora) occurring in the total sample area of 1.56m². Seaweed communities clearly change with depth, but the biggest change occurs between the shallow subtidal zone (approx 1 m depth) and deeper waters (&gt;5 m depth), mostly likely due to the effects of wave action; thereafter communities do change with depth, but the effects are less pronounced. Biomass (p=0.049, significant) and seaweed diversity (p=0.078, not significant) were both shown to decrease, and % bare (seaweed-free) cover (p=0.002, significant) increased, with increasing depth. It is likely that these changes with increased depth can be attributed to the effects of increased light attenuation on ecological functioning in the subtidal communities. Sand inundation patterns are shown to be important in determining seaweed community structure, but do not appear to be predictable along a depth gradient (p=0.544, not significant).