This study provides information on the biology, stock status and the management of C. puniceus, a key linefish resource in southern Mozambique. This is regionally endemic to Mozambique and KwaZulu-Natal. Fairly resident species, is found on the continental shelf ranging north to Zavora and south to KwaZulu-Natal and Transkei, and inhabits rocky seabeds, ranging between 20 and l00m. In Mozambique is manly exploited by semi-industrial fleet, and exported to South Africa. The reproductive biology, assessed through gonad somatic index as well as microscopic and macroscopic assessment, indicates that spawning extends over the spring months from August to November, peaking in September. It is a protogynous hermaphrodite, relatively slow growing and long lived species. The length-weight relationships for male and female C. puniceus show to be different, and the overall length frequency distribution shows clear difference in size between male and female C. puniceus, with male length frequency distribution restricted to the larger size classes. The monthly length frequency distribution of female C. puniceus is unimodal and peak at 300 mm FL, male shows unclear year classes. Age determination was carried out using otoliths and growth was estimated using the model developed by Punt et al (1993) for protogynous hermaphrodites reproductive styles. Validation of annuli was done by examining the outer margin of otolith, and also through mark and recapture information. Validation following the first method indicated that the opaque band is laid down twice a year, but the mark recapture results were inconsistent. This contradicts previously published information on C. puniceus, and thus; both single and double scenarios were modelled. The Von Bertalanffy growth parameters found for C. puniceus suggest relatively slow-growth, with the number of rings found from reading the sectioned otolith ranging from 2 to 18. Reproducibility of age estimates was evaluated using the average percentage error (APE) technique, and was equal to 22%. The age at full recruitment was found to be 2.5 and 5 years for bi-annual and annual banding, respectively. The analysis of the age-at-50% maturity, based on double band scenario, suggests that C. puniceus mature at 1.5 year-old, which corresponds to a mean FL of 240mm. A preliminary yield per recruit assessment revealed that at the current fishing mortality, C. puniceus fishery is moderately overfished, with the spawning biomass-per-recruit at 35.43% and 36.57%, for one and two bands, respectively, of its unexploited level. Fishing mortality was equal to 0.2 year-1 and 0.41 year-1, for single and double band, respectively. YPR analysis shows that the single band scenario is less conservative than the double band assessment, which has a bearing on the management approach. It is suggested as the preliminary management strategy a reduction of the number of boats. Indeed the average number of crew per boat, needs to be evaluated in terms of overall effort. To complement this management measures, there is a strong and urgent need to establish marine reserves in order to protect spawning stock, and also, to develop an overall linefish management plan, which will help in the management of the whole linefish resource in Mozambique. Furthermore, an age and growth study for C. puniceus over a larger geographical area needs to be done as a mean to overcome the differences between previous study and this study, once C. puniceus is being shared between the two countries (Mozambique and KwaZulu-Natal). / Thesis (M.Sc.)-University of Natal, Durban, 2001.

This study conducted the first high-resolution investigation of the ichthyofaunal assemblages on a high-latitude coral reef in the Western Indian Ocean (WIO). Two-Mile reef, in South Africa, is a large, accessible patch-reef, and was selected as a candidate study area. Although the effect of season in structuring coral reef fish communities is most-often overlooked, the relationship between these fish communities and their habitat structure has been investigated. In South Africa, however, neither of these potential community-level drivers has been explored. As coral reefs worldwide are faced with high levels of usage pressure, nondestructive underwater visual census (UVC) techniques were identified as the most appropriate survey methods. This study had two primary aims that were; (1) to identify the most suitable technique for the UVC of coral reef fishes, and to test variations of the selected technique for appropriateness to implementation in long-term monitoring programs, and (2) to determine if possible changes to ichthyofaunal community structure could be related to trends in season and/or habitat characteristics. A review of the literature indicated that the most appropriate UVC method for surveying epibenthic coral reef fishes is underwater transecting. To compare the traditional slate-based transects to variations that implement digital image technology, slate transects were compared to a first-attempt digital photographic transect technique, and digital videographic transects. Videographic transects produced the most favourable species richness, abundance, and standard deviations of the three techniques. Diversity was not significantly different between transect techniques. The minimum required sample size was lowest for videographic transects (17 replicates), intermediate for photographic transects (27 replicates) and highest for slate transects (37 replicates). Videographic and photographic transects required greater analysis time to generate counts, but required lower observer training time. While videographic transects produced the lowest proportion of species considered unidentifiable, all three transect techniques showed similar functionality to surveying epibenthic coral reef fishes. Videographic transects were therefore identified as the most appropriate UVC technique for this study. Videographic transects at shallow (6 – 14 m), intermediate (14 – 22 m) and deep (22 – 30 m) depths in mid-winter and mid-summer, sampled a total of 41 families consisting of 209 species and 18172 individuals, dominated by pomacentrids in abundance and labrids in richness. The fish assemblages on Two-Mile Reef were found to be similar in composition to lower-latitude WIO reefs. Overall ichthyofaunal abundance and richness was significantly higher in summer than in winter, and was higher at shallow sites than at intermediate and deep sites. A multivariate approach confirmed differences between seasons at shallow depths but not between seasons at intermediate and deep depths. The fish assemblages on Two-Mile Reef can therefore be described as being comprised of four relatively distinct communities: a shallow, winter community; a shallow, summer community; a year-round intermediate community; and a year-round deep community. The distributions of discriminating species indicated that high abundances of the algal-feeding pomacentrids are observed only at shallow and intermediate sites while high abundances of the zooplanktivorous serranid subfamily, the Anthiinae, are observed predominantly at deep sites. Assessment of all measured supplementary variables indicated that of all factor combinations, observed patterns could be ascribed most strongly to depth. Quantification of reef characteristics indicated that as depth increases, habitat complexity decreases, benthic communities shift from dense coral domination to sparse sponge domination, and algal biomass and cover decreases. The ability of the videographic transect technique to detect changes in community structure with season and depth indicates that season and depth should be accounted for in future high-latitude ichtyofaunal surveys, and that the videographic transect technique is suitable for implementation in long-term monitoring programs on coral reefs. The similarity in fish assemblages between Two-Mile Reef and lower latitude regions suggests that the protocol for surveying epibenthic coral reef fishes, resulting from this study, is relevant throughout the continental WIO.

Chrysoblephus puniceus is an over-exploited linefish species, endemic to the coastlines off southern Mozambique and eastern South Africa. Over-exploitation and habitat loss are two of the biggest threats to the sustainability of fisheries globally. Assessing the genetic stock structure (a prerequisite for effective management) and predicting climate related range changes will provide a better understanding of these threats to C. puniceus which can be used to improve the sustainability of the fishery. Two hundred and eighty four genetic samples were collected from eight sampling sites between Ponta da Barra in Mozambique and Coffee Bay in South Africa. The mitochondrial control region and ten microsatellite loci were amplified to analyse the stock structure of C. puniceus. The majority of microsatellite and mtDNA pairwise population comparisons were not significant (P > 0.05) although Xai Xai and Inhaca populations had some significant population comparisons for mtDNA (P < 0.05). AMOVA did not explain any significant variation at the between groups hierarchical level for any pre-defined groupings except for a mtDNA grouping which separated out Xai Xai and Inhaca from other sampling sites. SAMOVA, isolation by distance tests, structure analysis, principle component analysis and spatial autocorrelation analysis all indicated a single population of C. puniceus as being most likely. The migrate-n analysis provided evidence of current driven larval transport, with net migration rates influenced by current dynamics.Two hundred and thirty six unique presence points of C. puniceus were correlated with seasonal maximum and minimum temperature data and bathymetry to model the current distribution and predict future distribution changes of the species up until 2030. Eight individual species distribution models were developed and combined into a mean ensemble model using the Biomod2 package. Winter minimum temperature was the most important variable in determining models outputs. Overall the ensemble model was accurate with a true skills statistic score of 0.962. Binary transformed mean ensemble models predicted a northern and southern range contraction of C. puniceus' distribution of 15 percent; by 2030. The mean ensemble probability of occurrence models indicated that C. puniceus' abundance is likely to decrease off the southern Mozambique coastline but remain high off KwaZulu-Natal. The results of the genetic analysis support the theory of external recruitment sustaining the KwaZulu Natal fishery for C. puniceus. While the high genetic diversity and connectivity may make C. puniceus more resilient to disturbances, the loss of 15 percent; distribution and 11 percent; genetic diversity by 2030 will increase the species vulnerability. The decrease in abundance of C. puniceus off southern Mozambique together with current widespread exploitation levels could result in the collapse of the fishery. A single transboundary stock of C. puniceus highlights the need for co-management of the species. A combined stock assessment between South Africa and Mozambique and the development of further Marine Protected Areas off southern Mozambique are suggested as management options to minimise the vulnerability of this species.