Reef fish display station-keeping and ranging behaviour in the Pondoland Marine Protected Area on the east coast of South Africa

This study assessed the role of the Pondoland Marine Protected Area (MPA) in the Eastern Cape province of South Africa by evaluating retention versus ‘spillover’ of exploited fishery species that were tagged in a 400 km² no-take zone of the MPA. From April 2006 to July 2010, 2 124 fish comprising 36 species were tagged in the MPA, with an overall recapture rate of 23%. Findings for four important species (Polysteganus praeorbitalis, Chrysoblephus puniceus, Epinephelus andersoni and Epinephelus marginatus) are presented. Recapture rates ranged from 8% to 60% and time-at-liberty from 0 to 1 390 d. Individuals of all four species displayed highly localised station-keeping behaviour. For all four species, the 95th percentile of intra-study site movements was <750 m (linear distance) and many recaptures were within 250 m of the release site, showing that some fish spend most of their time in the MPA's no-take zone. However, some fish moved beyond the boundary of this zone in a north-easterly direction (range 3–1 059 km), where they would be available to the boat-based fishery in KwaZulu-Natal. The combination of resident individuals with some with ranging behaviour suggests that the MPA can provide a conservation role for these species, while exporting some individuals into nearby fisheries.     

Classification of marine bioregions on the east coast of South Africa

Marine bioregional planning requires a meaningful classification and spatial delineation of the ocean environment using biological and physical characteristics. The relative inaccessibility of much of the ocean and the paucity of directly measured data spanning entire planning regions mean that surrogate data, such as satellite imagery, are frequently used to develop spatial classifications. However, due to a lack of appropriate biological data, these classifications often rely on abiotic variables, which act as surrogates for biodiversity. The aim of this study was to produce a fine-scale bioregional classification, using multivariate clustering, for the inshore and offshore marine environment off the east coast of South Africa, adjacent to the province of KwaZulu-Natal and out to the boundary of the exclusive economic zone (EEZ), 200 nautical miles offshore. We used remotely sensed data of sea surface temperature, chlorophyll a and turbidity, together with interpolated bathymetry and continental-slope data, as well as additional inshore data on sediments, seabed oxygen and bottom temperature. A multivariate k-means analysis was used to produce a fine-scale marine bioregionalisation, with three bioregions subdivided into 12 biozones. The offshore classification was primarily a pelagic bioregionalisation, whereas the inshore classification (on the continental shelf) was a coupled benthopelagic bioregionalisation, owing to the availability of benthic data for this area. The resulting classification was used as a base layer for a systematic conservation plan developed for the province, and provided the methods for subsequent planning conducted for the entire South African EEZ. Validation of the classification is currently being conducted in marine research programmes that are sampling benthic biota and habitats in a sampling design stratified according to the biozones delineated in this study.     

Movement patterns of the parrotfish Sparisoma cretense in a Mediterranean marine protected area

Understanding the movements of exploited fish has become a major concern for several management and conservation initiatives, such as the implementation of well designed marine protected areas. Movements of an important recreational target species from the Mediterranean Sea, the parrotfish Sparisoma cretense, were determined in a marine protected area using passive acoustic telemetry, to evaluate site fidelity and homing, quantify home range and identify temporal patterns. Six adult parrotfish (20.8–29.8 cm total length) were caught along the north-eastern coast of Lampedusa (Italy) and surgically implanted with acoustic transmitters. Three fish were caught and released at the same site within the integral (i.e. “no entry-no take”) reserve, whereas the others were caught outside the reserve boundary and released at the mid reserve 0.5 km apart. Two of the three fish that were released away from the capture site demonstrated homing abilities. Four fish showed a strong site fidelity, whereas the others moved frequently in and out of the monitoring area. Home range sizes estimated over the period of monitoring (up to 207 days) varied from 70,387 to 256,398 m², with core areas of 16,688 to 84,946 m². Home range size did not differ significantly between day and night. Home ranges of all fish extended beyond the reserve boundaries, showing example of potential spillover into take zones. Temporal activity patterns of fish were diurnal with a dominant diel rhythm, likely due to a resting behaviour at night. Though not specifically designed to protect exploited fish, the marine reserve of Lampedusa seems adequate for the conservation and management of S. cretense.     

Towards the declaration of a large marine protected area: a subtidal ichthyofaunal survey of the Pondoland coast in the Eastern Cape,South Africa

A subtidal marine ichthyofaunal survey was carried out on shallow reefs (1–30m deep) in the Pondoland region between the Mtamvuna River and Port St Johns in the Eastern Cape, South Africa. The purpose of this survey was to provide the baseline data required for the zonation of a large marine protected area proposed for the region. Survey work was carried out in May and June during 2002 and 2003. A seafloor map based on earlier seismic-reflection profiling data, coupled with fishers' co-ordinates of known reefs in the area, was used to plan the survey. An underwater visual census (UVC), using the point-count method, assessed fish diversity, relative abundance and size structure. During the UVC, a total of 261 point fish-counts, covering an area of 14 288m², was completed. A total of 138 fish species from 49 different families was identified and a relatively high proportion of endemic species (26.6%) were recorded. As a result of the turbid conditions encountered south of Mbotyi, numbers and diversity of fish species observed declined with increasing latitude. Endemic sparid linefish species, which are overe-xploited in other areas, were particularly abundant in this region, and a number of new range distributions of various species were recorded during the survey. The results of this survey contributed towards the zonation of the Pondoland Marine Protected Area, which was proclaimed in June 2004.     

Nursery use patterns of commercially important marine fish species in estuarine systems along the Portuguese coast

Analysing the estuarine use patterns of juveniles of marine migrant fish species is vital for identifying important sites for juveniles as well as the basic environmental features that characterize these sites for different species. This is a key aspect towards understanding nursery function. Various estuarine systems along the Portuguese coast (Minho, Douro, Ria de Aveiro, Mondego, Tejo, Sado, Mira, Ria Formosa and Guadiana) were sampled during Spring and Summer 2005 and 2006. Juveniles of commercially important marine fish species Solea solea, Solea senegalensis, Platichthys flesus, Diplodus vulgaris and Dicentrarchus labrax, predominantly 0-group individuals, were amongst the most abundant species and had distinct patterns of estuarine use as well as conspicuous associations with several environmental features. Juvenile occurrence and density varied amongst estuaries and sites within them, and differed with species. Sites with consistently high juvenile densities were identified as important juvenile sites (i.e. putative nursery grounds). Through generalized linear models (GLM), intra-estuarine variation in occurrence and density of each of the individual species was largely explained by environmental variables (temperature; salinity; depth; percentage of mud in the sediment; presence of seagrass; importance of intertidal areas; relative distance to estuary mouth; macrozoobenthos densities; and latitude). Decisive environmental factors defining important sites for juveniles varied depending on the system as a result of different environmental gradients, though there were common dominant features for each species regardless of the estuary considered. Analysed environmental variables in the GLM also accounted for inter-estuarine variation in species' occurrence and density. In several estuaries, the identified important juvenile sites were used by many of these species simultaneously and may be of increased value to both management and conservation. Overall, the variability in site features amongst estuaries highlighted the tolerance of these species to different available environmental conditions and provided fundamental information for future spatially explicit modelling of their distribution. This should ultimately enable the prediction of species response to habitat alterations.     

Monitoring the recovery of a previously exploited surf-zone fish community in the St Lucia Marine Reserve,South Africa,using a no-take sanctuary area as a benchmark

Limiting accessibility to a fishing area can reduce fishing effort effectively and may therefore promote local recovery of depleted stocks. In January 2002, beach driving was banned in South Africa, thereby reducing angler access to large areas of the coastline, particularly in less-developed areas. In November 2001 a project had been established in the St Lucia Marine Reserve, on the east coast of South Africa, to compare surf-zone fish populations inside a no-take sanctuary zone with those in an adjacent exploited area. Subsequent to the ban, the aim of the project was adapted such that surf-zone fish populations were monitored for potential recovery in what had been the exploited area, located to the north of Cape Vidal, which anglers could no longer access easily, because of the prohibition on beach driving. Standardised research fishing was conducted at two sites in the previously exploited area and two sites in the no-take sanctuary. Conventional stock-status indicators showed evidence of recovery in the four most common species caught in the previously exploited area, in terms of both abundance and biomass. Generalised additive mixed models were used to account for the influence of targeting specific species; however, subtle differences in habitat between the sampling sites, improved angling skill over time, variability in recruitment, and differential species-specific responses complicated interpretation of results. The implications of the findings are discussed in terms of the future monitoring and management of marine protected areas both within the St Lucia Marine Reserve and farther afield.     

The 2005 KwaZulu-Natal sardine run survey sheds new light on the ecology of small pelagic fish off the east coast of South Africa

Despite much public awareness surrounding the annual migration of sardine Sardinops sagax northward along the east coast of South Africa in winter each year, relatively little research effort has been expended to improve understanding of the ‘sardine run’. For this reason, a dedicated multidisciplinary survey, timed to coincide with the annual sardine run, was conducted off the East Coast in June and July of 2005. The major objective of the survey was to estimate the biomass of sardine off the East Coast during the run, and to compare this with biomass estimates collected during previous surveys conducted in this area during the late 1980s when the South African sardine population was at a considerably smaller size. We also collected data on the distribution of sardine and other small pelagic fish species and their eggs, the biological characteristics of sardine during the run, and data on the hydrography (temperature and currents) and lower trophic levels (phytoplankton and zooplankton) of the region. Results suggest that the biomass of sardine off the East Coast in winter remains relatively small and consistent, regardless of overall sardine population size. The narrow continental shelf to the east of Port Alfred, which is dominated offshore by the fast-flowing warm Agulhas Current, constrains the amount of suitable habitat for sardine and other clupeoids such as anchovy Engraulis encrasicolus, West Coast round herring Etrumeus whiteheadi and East Coast round herring Etrumeus teres, and hence precludes these species from attaining a high biomass in this region. Additionally, primary and secondary productivity levels are much lower than elsewhere on the western and eastern Agulhas Bank off the south coast of South Africa, suggesting that the sardine run is not a feeding migration. A previous hypothesis that the run is mainly a result of an expansion of the distributional range of these fish as conditions become favourable in winter due to sporadic cooling off the East Coast is also not entirely supported by results from the survey. It is suggested that a migration for the purposes of spawning off this coast when conditions become favourable is a more likely incentive for sardine to undertake this arduous journey, despite increased predation and poor feeding conditions.     

Chlorophyll concentrations and suspended particulate loads in St Lucia,a turbid estuary on the east coast of South Africa

Concentrations of chlorophyll a and suspended particulate concentrations were measured during three lake-wide surveys of St Lucia, a shallow, turbid estuary on the east coast of South Africa. There was no salinity gradient in the system during any of the surveys, but between the surveys there were considerable salinity differences. Summer turbidities were higher than those of winter and spring, and turbidity along the eastern edge of the system was lower than elsewhere. Chlorophyll a was present over a wide range of salinities and turbidities and was generally highest in summer. However, there was no relationship between salinity and concentrations of chlorophyll a, and the concentrations were not significantly higher along the less turbid eastern shore. Concentrations of total paniculate matter (TPM) and particulate organic matter (POM) in the < 100 μm fraction were significantly correlated with turbidity throughout the year, but chlorophyll a and POM (< 100 μm) were significantly correlated only in summer. Concentrations of TPM in the > 100 μm fraction were two orders of magnitude lower than those in the < 100 μm fraction, but the organic content of the former fraction was very much higher. There was no relationship between turbidity and TPM (> 100 μm), nor between chlorophyll a and POM (> 100 μm) concentrations. Under conditions of high TPM load and in the salinity range 2–25 × 10^?3, phytoplankton would probably still occur in St Lucia. Estimates of phytoplankton production ranged between 218 and 252 mg C·m?2·day^?1. A comparison of estimates of the standing stocks of carbon from phytoplankton and suspended POM < 100 μm indicated that carbon input from sources other than phytoplankton may be important.     

Species composition,abundance and biomass of microphytoplankton in the KwaZulu-Natal Bight on the east coast of South Africa

Nearshore marine environments are influenced by an array of variables that can either be land-derived or of marine origin, and nearshore phytoplankton communities may differ in their taxonomic composition and biomass in response to such variables. The KwaZulu-Natal Bight (hereafter referred to as ‘the bight’) is an oligo-mesotrophic, nearshore oceanic environment, that is influenced by both terrestrial run-off and upwelling. A microphytoplankton survey of the bight conducted over several stations and depths and two seasons was conducted in order to ascertain species composition, abundance and biomass. Microphytoplankton abundance was generally low (a maximum of 180 000 cells l–1 was recorded) but differed considerably between sites and seasons. A total of 99 taxa of mainly Bacillariophyceae and some Dinophyceae, Prymnesiophyceae and Cyanophyceae were identified in the present study. In the central bight, higher abundance and biomass were measured in February (wet season), which may be a possible consequence of terrestrial nutrient inputs. In the northern and southern bight we measured higher abundance and biomass in August (dry season). Upwelling was not detected during the study, but an influence of terrestrial nutrient sources was detected at the coastal stations. Turbid conditions were specific to the site near the Thukela River mouth and possibly influenced abundance, biomass and species composition at this site. Historic data on microphytoplankton composition are scarce, but comparisons with surveys from the 1960s reveal that around 60% of the common diatoms recorded then also occurred in the present study. Small taxa [20–200 µm] dominated the microphytoplankton community. Community composition was fairly uniform throughout the bight in both seasons, dominated in general by Chaetoceros species, and on occasion co-dominated by Thalassionema nitzschioides and Dactyliosolen fragilissimus.     

Movement patterns of an endangered fishery species,Lithognathus lithognathus (Sparidae), and the role of no-take marine protected areas as a management tool

Understanding movement behaviour is essential for effective management of fishery species. Dart tags were used to study coastal movement patterns of white steenbras Lithognathus lithognathus, an overexploited seabream (Sparidae) in South Africa. In total, 6 962 fish (190–1 080 mm fork length) were tagged throughout the species’ distributional range, in four long-term fish-tagging programmes. The predominant behaviour recorded was residency, with relatively short-ranging movements. More than 60% of the 351 recaptured fish were recaptured within 1 km of their tagging site, some of which were at liberty in excess of three years. Most of the juveniles (93.9%), subadults (71.7%) and adults (64.0%) were recaptured within 10 km. Occasional long-distance movements of up to 800 km were recorded. Recapture distances were positively, but weakly, correlated with fish fork length (n = 257 fish measured at recapture; r² = 0.166, p < 0.001). Low levels of connectivity among coastal areas suggest that large-scale annual spawning migrations, as previously hypothesised for this species, are unlikely, which raises the possibility of multiple spawning sites. Seventy-seven percent of L. lithognathus tagged within three marine protected areas (MPAs) were recaptured within the same MPA, suggesting that area closures provide protection for L. lithognathus through the post-estuarine juvenile, subadult and adult life stages. We confirm that the country’s current network of coastal MPAs plays a vital role in sustaining this species, and suggest that additional closures, or otherwise substantial reductions in catch rates, are necessary for the species’ recovery.     

Movement patterns of the sea urchin Paracentrotus lividus in a marine reserve and an unprotected area in the NW Mediterranean

Sea urchins can alter the composition and dynamics of algal communities by grazing. Changes in their displacement capability can influence their grazing and thus their effect on algal communities. The daily and monthly movement of Paracentrotus lividus inside and outside a marine reserve in the NW Mediterranean Sea was studied in order to determine the role of predation in sea urchin movements and its potential grazing impacts. During the 3‐month study, the total distance travelled by sea urchins ranged from 71.8 to 673.6 cm (mean = 379.2 cm, SD = 221.3). Home ranges (distances from the initial position) were between 50 and 302 cm (mean = 150.7 cm, SD = 99.4). Movements were not directional but random, with a mean of 150 cm around the initial position. The activity of Paracentrotus lividus was significantly higher at night than during daylight. Total displacement at the end of the experiment was significantly higher in the unprotected area than in the reserve, as was the home range. The linear distance travelled in a 24‐h period ranged between 6 and 220 cm with a mean home range of 51 cm. These results agree with those of other authors, and allow us to rule out major migratory processes of sea urchin populations in this area. Nevertheless, these results underline the role of predatory fishes in reducing herbivory pressure by trophic cascades, reinforcing the evidence that sea urchin escape behaviour may be an important factor in structuring algal communities.     

Movement patterns of coastal bottlenose dolphins in the presence of a fast-flowing,prevailing current: shore-based observations at Cape Vidal,South Africa

The presence and movement of Indo-Pacific bottlenose dolphins Tursiops aduncus were investigated using shore-based observations made during a humpback whale Megaptera novaeangliae migration survey at Cape Vidal, South Africa, undertaken between June and October 1988–1991. Occurrence was analysed as counts of dolphin sightings per hour within a generalised estimating equation framework. Bottlenose dolphin sightings decreased throughout the daily survey period, and there was a small seasonal peak in sightings during August. Data on movement trajectory were collected using a theodolite for 60% of the groups of dolphins sighted. Most groups were observed travelling in a northerly direction, with few groups recorded moving south. A generalised linear model indicated that northward-travelling dolphins were located closer to shore, travelled at higher speeds, and occurred in bigger groups under low-tide conditions, than those seen moving in a southerly direction. The southward-flowing Agulhas Current is close to shore at Cape Vidal, where the continental shelf is particularly narrow. We suggest that bottlenose dolphins in this area have adopted a specific movement regime to cope with the consistent fast-flowing currents that dominate their environment at Cape Vidal.     

海上地震勘探主要采集参数的选取与验证——以南海北部某调查区为例

采集参数选取的优劣直接关系到野外地震资料质量的高低。作者经过多年海上地震调查实践,总结了一套实用的采集参数选取原则与验证流程。首先结合南海北部某调查区以往的地震和地质资料分析,建立了典型的地震地质结构模型;根据现有调查设备的性能,利用专业软件Nucleus6.2模拟对采集参数选取的理论计算,比较不同采集参数组合的模拟结果,选择有利于调查任务的参数组合。对海上生产前模拟选用的采集参数组合做试验和验证,确定了最适合的参数作业。运用该套原则和流程精心设计,实验获得了高质量野外资料。