Aspects of the reproductive biology of Sarpa salpa (Pisces: Sparidae) off the east coast of South Africa

The reproductive biology of the sparid fish, Sarpa salpa, was investigated along the east coast of South Africa between January 1994 and March 1995. A protracted winter spawning season was identified, extending from April through to September, and it was evident that S. salpa migrate annually to KwaZulu-Natal from juvenile nursery areas in the Eastern and Western Cape. Size at 50% maturity for male S. salpa was attained at 145 mm fork length, while the adult sex ratio in the shore-based catch was 1:1.6 in favour of males. Frequency distribution by size indicated that males dominated the smaller size classes while females dominated the larger size classes. Histological examination of gonadal development revealed five types of gonads, namely undifferentiated, juvenile, male, intersex, and female gonads. Intersex gonads were characterised by degenerating testicular tissue separated from a dormant ovary by connective tissue. The population demography and the presence of intersexual individuals with degenerating testicular tissue was suggestive of protandrous sex change in S. salpa. This was confirmed during a captive study in which male S. salpa changed sex to female. Group spawning behaviour is postulated based on various morphological and indirect behavioural characteristics

Age and growth of the estuarine-dependent sparid Acanthopagrus berda in northern KwaZulu-Natal, South Africa

Ages were estimated for the tropical sparid, Acanthopagrus berda, caught in northern KwaZulu-Natal estuaries. Whole otoliths were used in the age determination. Age estimates were validated by marginal increment analysis and oxytetracycline labelling, which indicated that opaque deposition occurs primarily from September to November each year. The reproducibility of age estimates was described by a coefficient of variation of 10%. The von Bertalanffy growth curve was found to best describe the growth of A. berda. The parameters of the von Bertalanffy growth curve indicated that A. berda in northern KwaZulu-Natal is a slow- growing species, capable of reaching at least 16 years of age. Longevity of the species, coupled with sex change, late maturation and estuarine dependency, give cause for concern for the continued sustainable utilization of this species

The recreational fishery in the Kosi estuarine lake system, South Africa

The Kosi estuarine system, located in northern KwaZulu-Natal, is becoming an increasingly popular angling venue. Recreational catch card data from the National Marine Linefish System for the years 1986 to 1999 were analysed to determine total catch, catch composition, catch per unit effort (CPUE), seasonality of catches and annual trends in catch composition. A total of 17 families, comprising 34 species, was reported in catches of recreational anglers. Pomadasys spp., predominantly Pomadasys commersonnii, was the most prominent taxon caught in terms of both numbers and mass. Seasonal trends in catch rates were observed, with more fish caught in the summer and autumn months. The catch rate fluctuated annually. Fluctuations in CPUE were closely correlated to the number of cards collected, which reflects bias in the data. Despite annual fluctuations in CPUE, regression analysis revealed a slight increase in overall CPUE with time. However, CPUE for Acanthopagrus berda and Lutjanus argentimaculatus decreased steadily since 1986. The decline of these two estuarine-dependent species may indicate that the total fishing levels are not sustainable

Trends in shore-based angling effort determined from aerial surveys: a case study from KwaZulu-Natal, South Africa

Understanding the spatiotemporal characteristics of effort is a critical component of managing fisheries. Recreational shore-angling is the largest sector of the linefishery and one of the primary recreational activities undertaken along the coast of KwaZulu-Natal (KZN), South Africa. The aim of this study was to make a reliable estimate of current total shore-based angling effort in KZN and to examine the spatial and temporal distribution of the effort. To do this, randomised monthly flights to count shore-anglers in an ‘instantaneous’ manner were conducted along the entire KZN coastline between January and December 2018, and then compared with similar aerial surveys conducted in 1994/95 and 2007/08. A total of 44 flights were undertaken, with 21 and 23 flights conducted along the north and south coasts, respectively. Ground-truthing revealed that the aerial counts of shore-anglers were 89% accurate. Angler effort was significantly higher over weekends and during good-weather days. Seasonality of shore-based angling effort showed that greatest effort occurred during the winter months (June to September), coinciding with the seasonal availability of popular angling species. More-developed stretches of the KZN coast with higher population densities and easier beach-access had the highest angling effort. Total annual angler effort was calculated to be 785 538 angler-days y–1, which represents a 22.9% decline from the estimate made in 1994/95 and a 6.9% decline from the estimate made in 2007/08. Spatial distribution of shore-based fishing effort was very similar in 2007/08 and 2018, with the major differences being a decrease in fishing effort at St Lucia and Maphelane, and a slight increase in effort on the ‘upper’ (northern) south coast during 2018. Based on the results of this study, recommendations for improved management of the KZN shore fishery include: (i) follow-up using an independent roving-creel survey; (ii) improvement of coastal law enforcement; (iii) implementation of a linefish observer programme; and (iv) a repeat of the aerial survey every 10 years. Keywords: angler counts, historical trends, marine linefishery, recreational fishing, seasonality, spatiotemporal distributio

Diets of <i>Diplodus sargus capensis</i> and <i>D. cervinus hottentotus </i>(Pisces: Sparidae) on the Tsitsikamma coast, South Africa

Diets of Diplodus sargus capensis and D. cervinus hottentotus, sampled on the Tsitsikamma coast, are described. D. sargus was a generalist, feeding on a wide variety of reef associated invertebrates and algae. D. cervinus was more of a specialist feeding on comparatively few prey groups, the most important being polychaetes and amphipods. Juveniles of both species showed considerable spatial and dietary overlap, feeding predominantly on amphipods, polychaetes and harpacticoid copepods. Larger fish showed an increase in the range of prey species taken and dietary overlap was diminished. The dietary differences between these two species are thought to contribute to greater abundance and habitat range in D. sargus

Age and growth of narrow-barred Spanish mackerel Scomberomorus commerson in the coastal waters of southern Mozambique and KwaZulu- Natal, South Africa

The narrow-barred Spanish mackerel Scomberomorus commerson is one of the most important linefish species caught in KwaZulu-Natal and southern Mozambique waters, forming the basis of important commercial, artisanal and recreational fisheries. A total of 439 S. commerson were sampled along the east coast of southern Africa (KwaZulu-Natal, South Africa, and southern Mozambique) between April 2011 and March 2012. Retrospective length-at-age data observed from whole otoliths were used to compare and describe sex-specific growth. Growth rates obtained from otolith-derived data were compared with those estimated from 29 tag-recaptured fish. Overall, ages ranged from 0.48 to 14.6 years for females and 0.4 to 13.57 years for males. Otolith readings yielded an average percent error of 11.21%, lower than recorded in a previous study from the region. Marginal zone analysis provided strong evidence that one translucent and one opaque growth zone were laid down annually. Schnute growth-function parameters indicated significant differences in growth between sexes. Females approached their mean asymptotic length at a faster rate, and grew to a greater mean length-at-age, relative to males. Growth in both sexes was rapid, achieving 67.46 cm FL (females) and 65.4 cm FL (males) in their first year of life. Growth rates obtained from tag-recaptured S. commerson indicated slower growth for smaller/younger fish up until 70 cm FL after which growth was very similar to that observed from otolith-derived data. The results of this study provide accurate, validated life-history parameters for king mackerel that are important for the assessment of stock status in the region.Keywords: back-calculation, growth estimates, otolith ageing, recreational fishery, Schnute model, Scombridae, sex-specific growth, tag-recapture dat