Contributions to the functional morphology of fishes

Zoologica Africana 2 (1): 69-8

The responses of South African patellid limpets to invertebrate predators

The starfish Marthasterias glacialis is a generalized predator, feeding particularly on Choromytilus meridionalis, but also on several limpets, notably Patella longicosta. Thais dubia (Gastropoda) feeds mainly on barnacles, mussels, and Patella granulans. The gastropods Burnupena delalandii and B. cincta are principally scavengers, feeding on damaged or dead animals. The responses of Patella spp. to these predators are described. P. granulans, P. concolor, P. compressa and P. miniata all retreat rapidly on contact. Small P. granatina and P. oculus respond similarly, but larger specimens react aggressively, smashing their shells downwards and often damaging the predator. The territorial species (P. longicosta, P. cochlear and P. tabularis) all retreat to their scars and remain clamped there. P. argenvillei and P. tabularis are usually unresponsive, possibly because they are too large to fall prey. Cellana capensis rolls its mantle upwards to cover the shell, preventing predators from attaching. The responses and their effectiveness are discussed in relation to other behavioural patterns displayed by limpets. There is no correlation between the intensity of a prey’s response to a predator and the degree of contact between the two in the field

Book ReviewAdvances in Littorinid Biology. Proceedings of the Fourth International Symposium on Littorinid Biology, Roscoff, France 1995

Kluwer Academic Publishers, Dordrecht193 pp.Price US$157.50 or £101S. Afr.J Zool. 1997,32(3

Criteria, objectives and methodology for evaluating marine protected areas in South Africa

In the face of ever-increasing requests for the proclamation of Marine Protected Areas (MPAs) in South Africa, there is a need to develop an objective protocol for their evaluation. To achieve this, a methodologyis described for which the acronym “COMPARE” (Criteria and Objectives for Marine Protected ARea Evaluation) is coined. COMPARE also allows existing MPAs to be evaluated in terms of their efficacy, and can assess the effects of changes to either legislation or management of existing MPAs. As a first step, 14 objectives are defined that may be met by MPAs. These fall into three categories: biodiversity protection, fisheries management and human utilization. A series of criteria were then proposed which can be used selectively to quantify the degree to which MPAs meet these objectives. Each of the objectives is scored against the appropriate criteria in a semi-quantitative manner that allows areas to be compared, either overall or in terms of specific objectives. Simply by comparing the degree to which different types of MPAs might meet these objectives, it is clear that fishery reserves, proclaimed for the protection of individual commercial species, meet an extremely limited suite of objectives compared with marine sanctuaries that protect all species, or marine reserves, which protect all but a few species. Prominent among the advantages of COMPARE are that it compels an examination of all possible objectives, pinpoints the reasons for decisions, identifies issuesthat need resolution and requires development of management plans. Its primary strategic advantage is that its implementation should lead to a rationally planned and defensible network of MPAs that will contributeto the conservation of marine biodiversity in South Africa

Relationships between recruits of abalone haliotis midae, encrusting corallines and the sea urchin Parechinus angulosus

In kelp beds of the South-Western Cape, South Africa, a strong positive relationship exists between the sea urchin Parechinus angulosus and juveniles of the abalone Haliotis midae. Field surveys reported here revealed apositive, but weak, association between this urchin and H. midae recruits (i.e. individual

The influences of physical factors on the distribution and zonation patterns of south african rocky-shore communities

Vertical zonation and horizontal distribution patterns of both community biomass and species richness of rocky-shore marine invertebrates and algae are described at a broad geographic scale for seven West andseven South-East Coast intertidal rocky-shore communities situated between southern Namibia and KwaZulu-Natal, South Africa. There were consistent patterns for community biomass and species richness, bothof which showed similar vertical and horizontal distributions in equivalent habitats, regardless of geographical location. This indicates that the processes which create these patterns operate and vary in a similar way, even between different geographical regions. Multivariate techniques were used to assess, at a local scale, the relative importance of wave energy, rock temperature and shore elevation on the structuring and spatialvariability of community biomass. Direct gradient analyses revealed that wave action strongly influences the structure of mid- to low-shore communities, whereas the interaction between rock temperature and shoreelevation (both of which influence desiccation potential) produces convergence of high-shore communities. There was a significantly positive relationship between wave action and the per-unit-area communitybiomass, and a negative relationship between shore elevation and biomass. The potential role that waves may play in determining overall intertidal productivity is discussed

Mass mortality and recolonization of pyura stolonifera (heller) on the south coast of South Africa

A mass mortality of the ascidian Pyura stolonifera (red-bait) was recorded along the Tsitsikamma coast of South Africa in May 1991, following the infection of a large proportion of the population with a white microbialgrowth. At nine subtidal red-bait beds, reductions in percentage cover of red-bait were greatest on the crests of reefs (42 ± 17%:1SD) and lowest on the landward edges (17 ± 8%). The test of P. stolonifera appeared to be the main site of the microbial infection. Scanning electron and epifluorescent microscopy revealed much higher numbers of bacteria on the tests of infected individuals (64.3 ± 5.5 × 106·mm-2) compared to healthy ones (5.1 ± 0.1 × 106·mm-2). Fat, curved rod bacteria and thick chains, which accounted for more than 45% of the bacteria on infected red-bait tests, were absent from the tests of healthy red-bait. Standard characterization techniques, coupled with API tests, showed that the isolates from infected red-bait tests belonged exclusively to thegenus Vibrio, whereas isolates from healthy tests included the genera Vibrio, Pseudomonas, Aeromonas and Flavobacterium/Cytophaga. The mass mortality therefore appeared to be associated with the proliferation of large curved rod bacteria of the genus Vibrio. Recolonization by P. stolonifera into areas naturally denuded of red-bait was significantly faster than for experimental plots cleared of all organisms during the mid 1980s. A mean cover of 33 ± 4% was recorded for P. stolonifera after 38 months following natural mortality, whereas it took 71 months to achieve a comparable recovery of 35 ± 20% in experimental plots. Possible reasons for this difference (viz. substratum, recruitment and predation) are explored

Diet of the west coast rock lobster Jasus Lalandii: Influence of lobster size, sex, capture depth, latitude and moult stage

Diets of male and female West Coast rock lobster Jasus lalandii in South Africa were compared across a large size range of 10–85 mm carapace length (CL). The diets of male rock lobsters were compared betweentwo different depths, different seasons, across the moult cycle, and among eight sites along the South-Western Cape coast. There was no significant difference in diet between male and female rock lobsters for any of thesize-classes examined. Male rock lobsters showed large differences in diet between small and large size-classes. The diet of small lobsters (80mm CL) fed on few species, and fish and ribbed mussels were their most abundant prey items. There were some dietary differences between individuals captured at 20 m and those collected at 50 m, but these differences were less marked than between the two sampling sites (the Knol and Olifantsbos). There was seasonal variation in diet at the Dassen Island and Olifantsbos sites. Cannibalism was highest during the moulting periods. Gut fullness varied seasonally at Dassen Island, and was consistently high at Olifantsbos. However, the proportion of the population feeding showed marked seasonal trends at both sites, tracking the commercial catch per unit effort of rock lobster. Ribbed mussels were a ubiquitous and dominant component of the diet at the eight sites sampled. However, south of Dassen Island, black mussels Choromytilus meridionalis were scarce in the diet of rock lobster and sponges predominated. Gut fullness was lowest at the northernmostsites

Defining fishers in the South African context: subsistence, artisanal and small-scale commercial sectors

Evolution of a new policy for the management of marine fisheries in South Africa led to the Marine Living Resources Act of 1998 (MLRA). Among other innovations, this requires that management strategies be developed for subsistence fisheries. As a prerequisite, definitions and criteria are needed to identify and distinguish them. To achieve this, the Chief Director of Marine & Coastal Management (MCM), the authority responsible for managing marine fisheries, appointed a Subsistence Fisheries Task Group (SFTG) to make recommendations about definitions and modes of management. The process involved successive surveys and consultations with fishing communities, communication with MCM, and a national workshop of all participants. This led to consensus about the following definition: Subsistence fishers are poor people who personally harvest marine resources as a source of food or to sell them to meet the basic needs of food security; they operate on or near to the shore or in estuaries, live in close proximity to the resource, consume or sell the resources locally, use low-technology gear (often as part of a long-standing community-based or cultural practice), and the kinds of resources they harvest generate only sufficient returns to meet the basic needs of food security. This definition builds on the facts that existing subsistence fisheries are usually: (1) local operations; (2) customary, traditional or cultural; (3) undertaken for personal or family use; (4) primarily for nutritional needs (though excess resources may be sold to ensure food security); (5) based on minimal technology; and (6) undertaken by people with low cash incomes. They are specifically non-commercial and non-recreational. The definition was designed to allow protection of the rights of these people and sustainability of the resources. While developing this definition, it became obvious that the definition of “commercial fishing” in the MLRA is also inadequate, and a new definition was developed. Commercial fisheries span a wide spectrum, and the SFTG defined “small-scale commercial fishers” as a distinct component that has not received adequate attention, and for whom specific management plans need to be developed. They are distinguished by living on or close to the coast, having a history of involvement with fishing, being personally involved in hands-on day-to-day running of their enterprises, operating with limited amounts of capital investment and low levels of technology, and employing small numbers of people.Keywords: defining subsistence, fisheries management, subsistence fishersAfrican Journal of Marine Science 2002, 24: 475–48

Case studies on the socio-economic characteristics and lifestyles subsistence and informal fisheries in South Africa

To develop a management strategy for informal fishers, a necessary first step is information about the nature of these fishers, their numbers and their socio-economic status. To accomplish this, a survey of socio-economic conditions and use of marine resources was undertaken in 1999 at 20 localities where fishing occurs around the coast of South Africa, concentrating on subsistence or small- to micro-scale artisanal commercial fishers. In each locality, 16–31 “fisher households” were surveyed by questionnaires, focus-group discussions and interviews with key informants. Demographic analyses revealed a low level of migrancy (~5%), an average of 5.3 persons per household and a mean age of 27. Only ~20% of fishers were women and ~15% were children. Poverty was prevalent: unemployment averaged 40.3% (much higher than the national norm of 29.3%). Mean adult equivalent income per month spanned R193–R735 among regions, and was not correlated with size of settlement. Education levels were low, only ~33% of people >20 years old having completed primary school. Migrancy was highest in rural areas (but still much less than the national norm), intermediate in towns and least in metropolitan areas. Household size, participation of women and poverty all followed similar trends. Comparing regions, the East Coast and the province of KwaZulu-Natal had higher migrancy rates, larger household sizes, greater poverty, and greater participation by women in fishing, than on the South and West coasts. Household expenditure on food was ~R450 per month on the South-East and KwaZulu-Natal coasts and ~R750 on the West Coast, and exceeded 60% of income (a measure of “food security”) in about half the households surveyed. Harvested resources were sold, consumed or used as bait. In all regions, the two most frequently harvested resources were fish (mostly sold, predominantly fished by men) and intertidal rocky-shore invertebrates (largely consumed, and involving women to a greater degree). On the West Coast, rock lobster Jasus lalandii was the third-most important resource, but on the South and KwaZulu-Natal coasts this species was replaced by estuarine invertebrates. Abalone Haliotis midae, oysters, sandy-beach invertebrates and kelp or seaweeds made up the balance. Diversity of harvested resources increased west to east, following biogeographic trends. The resources could be divided into those of high value (rock lobsters, abalone and, to a lesser extent, fish) and those of lower value (such as limpets, mussels and bait organisms). It is argued that high-value resources are best used to create micro- and small-scale commercial enterprises that can serve to uplift poor fishers. Lowvalue resources constitute subsistence resources, for which preferential rights should be established for subsistence fishers, including development of exclusive-use zones where necessary. Emerging characteristics of fishing communities that were helpful in defining subsistence fishers in the South African context were poverty, harvest for self-use (whether by consumption or sale to meet basic needs of food security), use of low-technology gear, and concentration of effort on or from shores or in estuaries. At least portions of the catches of all resources are sold, and the majority of equipment is purchased, so any definition of subsistence fishers cannot exclude those who sell part of their catch or do not use hand-made equipment. Some success was evident with co-management, encouraging further exploration of this style of management for subsistence fishers. Keywords: informal fishers, socio-economics of fishers, subsistence fishersAfrican Journal of Marine Science 2002, 24: 439–46