Cape Recife Research Articles

An investigation of sea level and circulation response during a coastal trapped wave event on the Eastern Agulhas Bank, South Africa

Coastal trapped waves (CTW) have the potential to capture and transport a significant amount energy from atmospheric wind systems, in turn inducing sudden changes to the coastal marine environment over large areas, even those remote to the propagating wind system. In this study, the effects of a large, eastward travelling CTW that was captured on in situ moored acoustic doppler current profiler (ADCP) (∼30 m bottom depth) and sea level recording instrumentation in Algoa Bay on the eastern Agulhas Bank off South Africa is examined using a high-resolution (dx∼1 km) Regional Oceanographic Modelling System (ROMS) ocean model. Alongshore current reversals to the full depth were seen in both the model and two ADCP moorings as the CTW traversed the study domain, with strong currents exceeding 1 m/s developing directly to the south of Cape St Francis and Cape Recife at the peak of the event within the model. In a special model run with surface wind stresses removed, it was shown that the CTW carries much of the energy into the domain from remote wind forcing to the west, contributing an estimated 82% of the eastward flux of shelf water. The total volume of water displacement during the CTW was estimated at 335.2 x 109 m3 which balanced (completion of a full wave cycle) over a period of 150h after the initial zero-crossing point of the transport flux.

Ecological value of the earliest human manipulated coastal habitats: Preliminary insights into the nursery function of a pre-colonial stonewalled fish trap in South Africa

Pre-colonial stonewalled fish traps, an ancient engineering feat in the intertidal region, represent the earliest proof of human manipulation of the coastline in Southern Africa, specifically by the First Indigenous Peoples of South Africa. We investigated the ecologically functioning of a fish trap located on the southeast coast of South Africa from a larval fish and invertebrate perspective. This research was done in collaboration with the Khoi traditional custodians of the area of study. Samples were collected using a light trap on four separate spring tide occasions, deployed for 3 consecutive nights during 2 full moon trips and 2 new moon trips during the known peak larval settlement period (November 2020–February 2021). Although time-dependent, the importance of this novel microhabitat for the development of coastal fishes and invertebrates was highlighted. Even with the high intertidal location of the stonewalled fish trap sampled at Cape Recife, the presence of a pool of permanent non-stagnant water within the fish trap, even during low spring tide, could provide protection to larvae, in the form of more stable environmental conditions, as well as less exposure to marine predators and harsh physical environmental conditions. This research aims to raise awareness of the stonewalled fish traps located on the southeast of South Africa with a view towards developing a more inclusive management of these marine cultural heritage sites, specifically involving the First Indigenous Peoples of South Africa.

Modelling regional and local-scale larval seeding strategies for abalone (H. midae) ranching in South Africa

Understanding connectivity between abalone populations and residence times for pelagic larvae within suitable settlement habitats is critical for sustainable management of wild abalone stocks and ranching schemes. In the Eastern Cape region of South Africa, poaching has severely depleted wild abalone Haliotis midae populations. Rebuilding stock through larval seeding is being considered as a potentially viable method, though is hampered by a limited understanding of abalone habitat connectivity through larval dispersal, both at a regional and local scale. To address this shortcoming, we apply a multi-scale approach to investigate potential larval dispersal along the coastline of Eastern Cape, South Africa, examining both intra- and inter-site connectivity, with the primary focus at the local nearshore scale (< 40 m water depth) where surf zone processes have a strong influence. Delft3D is applied at a regional scale (400-km domain) and XBeach is used at a local scale (5-km domain) to model a known abalone habitat at Cape Recife at high-resolution (5-m cell size). Models were validated using field observations. Complex topo-bathymetry data for the local-scale model domain around Cape Recife were obtained using a state-of-the-art low-cost multi-method surveying approach. At a regional scale, sites with abalone habitat have the potential to be connected across distances of 50–100 km. However, a large sandy embayment (Algoa Bay; 100-km arc length) is likely to present an obstacle to larval transport in all but the most extreme and sustained wind and wave forcing conditions. The central Cape Recife abalone ranching area has the potential to act either as a self-seeding or meta-population connected site, depending on forcing conditions. At the local scale around Cape Recife, a zone of shallow gullies, under lower-energy waves, was determined to be the optimal release point to maximise residency times within the preferred rocky, shallow subtidal habitat of H. midae. Competent larvae released in this zone are predicted to have an order of magnitude greater residency than randomly seeded larvae. This study provides site-specific connectivity and residence time information for the Eastern Cape abalone fishery, but more generally it provides a novel multi-scale method to aid in planning and managing of abalone larval seeding for ranching and stock enhancement programs that could be applied in other locations.

Conserved bacterial genomes from two geographically isolated peritidal stromatolite formations shed light on potential functional guilds.

Stromatolites are complex microbial mats that form lithified layers. Fossilized stromatolites are the oldest evidence of cellular life on Earth, dating back over 3.4 billion years. Modern stromatolites are relatively rare but may provide clues about the function and evolution of their ancient counterparts. In this study, we focus on peritidal stromatolites occurring at Cape Recife and Schoenmakerskop on the southeastern South African coastline, the former being morphologically and structurally similar to fossilized phosphatic stromatolites formations. Using assembled shotgun metagenomic analysis, we obtained 183 genomic bins, of which the most dominant taxa were from the Cyanobacteria phylum. We identified functional gene sets in genomic bins conserved across two geographically isolated stromatolite formations, which included relatively high copy numbers of genes involved in the reduction of nitrates and phosphatic compounds. Additionally, we found little evidence of Archaeal species in these stromatolites, suggesting that they may not play an important role in peritidal stromatolite formations, as proposed for hypersaline formations.

Living phosphatic stromatolites in a low-phosphorus environment: Implications for the use of phosphorus as a proxy for phosphate levels in paleo-systems.

In the geological record, fossil phosphatic stromatolites date back to the Great Oxidation Event in the Paleoproterozoic, but living phosphatic stromatolites have not been described previously. Here, we report on cyanobacterial stromatolites in a supratidal freshwater environment at Cape Recife, South African southern coast, precipitating Ca carbonate alternating with episodes of Ca phosphate deposition. In their structure and composition, the living stromatolites from Cape Recife closely resemble their fossilized analogues, showing phosphatic zonation, microbial casts, tunnel structures and phosphatic crusts of biogenic origin. The microbial communities appear to be also similar to those proposed to have formed fossil phosphatic stromatolites. Phosphatic domains in the material from Cape Recife are spatially and texturally associated with carbonate precipitates, but form distinct entities separated by sharp boundaries. Electron Probe Micro-Analysis shows that Ca/P ratios and the overall chemical compositions of phosphatic precipitates are in the range of octacalcium phosphate, amorphous tricalcium phosphate and apatite. The coincidence in time of the emergence of phosphatic stromatolites in the fossil record with a major episode of atmospheric oxidation led to the assumption that at times of increased oxygen release the underlying increased biological production may have been linked to elevated phosphorus availability. The stromatolites at Cape Recife, however, form in an environment where ambient phosphorus concentrations do not exceed 0.28μM, one to two orders of magnitude below the previously predicted minimum threshold of >5μM for biogenic phosphate precipitation in paleo-systems. Accordingly, we contest the previously proposed suitability of phosphatic stromatolites as a proxy for high ambient phosphate concentrations in supratidal to shallow ocean settings in earth history.

New species in the sponge genus Tsitsikamma (Poecilosclerida, Latrunculiidae) from South Africa.

The genus Tsitsikamma Samaai & Kelly, 2002 is to date exclusively reported from South Africa. Three species are known from the southern coast: Tsitsikamma favus Samaai & Kelly, 2002, from the Garden Route National Park Tsitsikamma Marine Protected Area (MPA) and Algoa Bay; T. pedunculata Samaai, Gibbons, Kelly and Davies-Coleman, 2003, collected from Cape Recife in St. Francis Bay, and T. scurra Samaai, Gibbons, Kelly and Davies-Coleman, 2003, collected from a wreck site in a small bay west of Hout Bay on the west coast of South Africa. Here two new species are described: Tsitsikamma michaeli Parker-Nance, sp. nov., a small green purse-like species, collected from Algoa Bay, and Tsitsikamma nguni Parker-Nance, sp. nov., from The Garden Route National Park, Tsitsikamma MPA. Additional morphological characteristics, spicule morphology, and distribution records are provided for T. favus and T. pedunculata from Algoa Bay. The phylogenetic relationship of these five Tsitsikamma species is investigated.

Assessing the accuracy of satellite derived ocean currents by comparing observed and virtual buoys in the Greater Agulhas Region

In this study, we assess the accuracy of a combined geostrophic and Ekman current product (GlobCurrent) that estimates ocean currents at 15 m depth, by coupling it to a synthetic particle tracking tool and comparing the virtual trajectories to those of surface drifting buoys drogued at 15 m in the Greater Agulhas Current Region. The velocities from a total of 1041 drifters are compared and evaluated to the synthetic particle-derived velocities for the period 1993–2015. On average the GlobCurrent underestimates the velocity in the Greater Agulhas Current by approximately 27%. The underestimation ranges from 4 to 64% in different regions, with the smallest error found in the Agulhas retroflection region, and the highest in the Benguela Upwelling System. Furthermore, we compare the time taken for the separation between the virtual and real drifters to reach 35 km. The mean separation time was found to be 78 h, with the shortest time (35 h) found in the Agulhas Current and the longest time (116 h) located in the Agulhas Return Current. Deploying 10,000 virtual drifters in a 1° × 1° box within the southern Agulhas Current shows a convergence of trajectories towards the core of the current, while higher divergence is evident in the Agulhas retroflection. To evaluate the utility of this synthetic particle tracking tool coupled with GlobCurrent in open ocean search and rescue operations, two test cases are examined: (1) a capsized catamaran spotted south of Cape Recife and recovered 5 days later south of Cape Agulhas; and (2) a drifter trajectory in the same region. The comparison suggests that the GlobCurrent forced synthetic particle tracking tool is not appropriate for predicting the trajectory of a capsized catamaran that does not have the same drift characteristics as a surface drifting buoy drogued to 15 m.

Another dolphin in peril? Photo‐identification, occurrence, and distribution of the endangered Indian Ocean humpback dolphin (Sousa plumbea) in Algoa Bay

Abstract In South Africa, the humpback dolphin (Sousa plumbea) has been recognized as the most endangered marine mammal, with a low abundance, a discontinuous distribution, and numerous threats. This research was initiated in 2008 to estimate the number of individual humpback dolphins in Algoa Bay, as well as studying their residency patterns and distribution. The last boat‐based study on humpback dolphins, conducted 24 years ago, formed an important reference against which to compare current findings. This study reveals that since the 1990s the number of identified animals decreased from 70 to 50 individuals, and the mean group size of humpback dolphins has also decreased, from seven to three animals. Humpback dolphin behaviour was predominantly that of foraging and travelling, although the overall frequency of foraging still seems to have decreased since early 1990s. Although the species was seen almost all year round, the number of sightings per survey was lowest in January, March, and April. The number of sightings per kilometre surveyed substantially decreased from 0.018 sightings per kilometre in 2008 to 0.004 in 2011, and the number of animals per kilometre also decreased from 0.042 to 0.009. The re‐sighting rates were low, ranging from one to eight times, with 52% of identified dolphins seen only once throughout the study period. Only 6% of the individuals were seen more than three times. Reduced humpback dolphin numbers and sighting rates could be indicative of the rise in anthropogenic activities, such as shipping and recreational boating, as well as a rise in pollution from vessels and urban development. Conservation strategies, such as a Biodiversity Management Plan for the species, are urgently needed in Algoa Bay, especially in the south‐west part of the bay, between Cape Recife and the Port Elizabeth Harbour, where the species occurs most frequently.

Plant selection and grazing activity of the invasive snail Theba pisana in coastal Algoa Bay, South Africa

The land snail Theba pisana is a coastal species native to the Mediterranean but has been introduced to regions all over the world, including South Africa and Australia, where it is considered a pest. This study examines the diet of T. pisana and its preference for certain dune plants in the Cape Recife Nature Reserve of Algoa Bay in the Eastern Cape, South Africa. Field observations identified plants being fed on by T. pisana, accounting for almost half of the dune plant species present in the study area. Five plant species, on which snails were found frequently and in high abundance, were selected for feeding preference experiments. Laboratory experiments and field observations indicate that T. pisana feed preferentially on Tetragonia decumbens over Osteospermum moniliferum, Osyris compressa and Cynanchum obtusifolium. It is clear that while T. pisana is reported to have a generalist diet, consuming a range of plant species commonly found in South African dune vegetation, it also exhibits a definite preference for T. decumbens. The reasons for this preference need to be investigated further.

Coastal upwelling on the far eastern Agulhas Bank associated with large meanders in the Agulhas Current

Six large solitary meanders in the Agulhas Current, so-called Natal Pulses, propagated down the eastern coast of South Africa between 2009 and 2011. Their influence on the coastal waters between Port Alfred and Algoa Bay, on the far eastern Agulhas Bank, was measured by thermistor strings moored at 30–80m bottom depths and two current metres (30m bottom depth) located at both sides of Algoa Bay. During all events active upwelling lasting 1–3 weeks was observed over the inner shelf and in Algoa Bay. During upwelling the isotherms ascended at an average rate of 1.8mday−1 as the cold bottom layer increased in thickness to 40–60m, although upwelled water did not break the surface in all cases. Cold water remained in the area for a further 2–3 weeks. During three Natal Pulses the water temperatures at the outer moorings initially increased as the plume of the leading edge (crest) of the meander moved onshore. During one Natal Pulse upwelling was recorded before the warm water plume impacted the moorings. At the onset of upwelling currents switched to the southwest in the case of Bird Island and southward at the Cape Recife inner-bay site and reached a maximum speed of 80cms−1. During all Natal Pulses cold bottom water (10–12°C) flooded over the 80m bottom depth moorings as the crest of the meander moved onshore, but also around the same time the core of the Agulhas Current began to move offshore. In all cases upwelling was wide-spread.

Seasonality, behaviour and philopatry of spotted ragged‑tooth sharks Carcharias taurus in Eastern Cape nursery areas, South Africa

Spotted ragged‑tooth sharks Carcharias taurus occur along the southern and eastern coasts of South Africa. We report on movements of juveniles and adults within a known nursery area on the Eastern Cape coast using acoustic telemetry. The focus area of the study was Algoa Bay, where six VEMCO VR2 ultrasonic receivers were placed at known shark aggregation sites. An additional receiver was placed at Thunderbolt Reef, approximately 2 km south‑ west of Cape Recife, the south‑western tip of Algoa Bay. Single receivers were also deployed at Port Alfred and East London, some 45 and 170 km north‑east of Algoa Bay, respectively. VEMCO acoustic V16 tags were either surgically implanted (n = 37) or attached externally using dart heads (n = 6) between January 2003 and March 2006. Surgically implanted tags were recorded over multiple months and years, whereas external tags were probably lost shortly after tagging because they were detected for very short periods. Sharks moved extensively between the sites and revisited monitored reefs over time‑periods of months and years, demonstrating philopatry. Departures from and arrivals at reefs were more frequently recorded at sunset and sunrise, respectively. Sharks were detected throughout the year but they spent more time at aggregation sites during summer and autumn, indicating seasonal abundance in agreement with previous findings. Movements away from study reefs were attributed to either foraging or movements to other reefs. Despite extensive movements around the bay and beyond, both juveniles and adults exhibited philopatry to the study area over multiple years.

Tufa stromatolite ecosystems on the South African south coast

Following the first description of living marine stromatolites along the South African east coast, new investigations along the south coast have revealed the occurrence of extensive fields of actively calcifying stromatolites. These stromatolites have been recorded at regular distances along a 200-km stretch of coastline, from Cape Recife in the east to the Storms River mouth in the west, with the highest density found between Schoenmakerskop and the Maitland River mouth. All active stromatolites are associated with freshwater seepage streams flowing from the dune cordon, which form rimstone dams and other accretions capable of retaining water in the supratidal platform. Resulting pools can reach a maximum depth of about 1 m and constitute a unique ecosystem in which freshwater and marine organisms alternate their dominance in response to vertical mixing and the balance between freshwater versus marine inflow. Although the factors controlling stromatolite growth are yet to be determined, nitrogen appears to be supplied mainly via the dune seeps. The epibenthic algal community within stromatolite pools is generally co-dominated by cyanobacteria and chlorophytes, with minimal diatom contribution.

Shell Use, Population Structure, and Reproduction of the Hermit Crab, Clibanarius virescens (Kraus, 1843) at Cape Recife, South Africa

Clibanarius virescens (Krauss, 1843) is one of the most common and abundant hermit crabs in South Africa and in the Indo-West Pacific region, but little is known about its population structure or breeding in Africa. Cape Recife, South Africa, is the south-western limit of its distribution and was sampled over a 13-month period to determine shell use, population structure, reproductive output and breeding period of C. virescens. Shells of 17 gastropod species were found in use with Burnupena lagenaria predominating (73.4% of shells used). Males and females appear to partition the shell resource. Males use larger shells of the same types as females, but also use different suites of shells. The sex ratio is 1 : 1.77 in favour of females, but males dominate the largest size classes. The breeding season occurs from mid-December to mid-July and ovigery correlates closely to sea surface temperature. Clutch size correlates strongly to crab size and shell volume. The population of C. virescens at Cape Recife has similar patterns of shell use as at other localities in Africa, but shows much larger clutch sizes than previously recorded in South Africa. This indicates that its life-history strategy at Cape Recife may differ from that at other localities within its range.

Profile of the illegal abalone fishery ( Haliotis midae) in the Eastern Cape Province, South Africa: Organised pillage and management failure

Since 1997 the Eastern Cape of South Africa has become a major source of supply for the illicit abalone trade as illegal fishers have located a substantial abalone ( Haliotis midae) resource. We determined illegal fishing effort and yield in the Port Elizabeth-based abalone fishery, and used biological indices to determine the impact of fishing on the abalone stock. The failure of the state to issue fishing rights and conduct effective sea-based compliance, combined with the incentives to fish abalone (high price, low cost, ease of access) created the conditions for a full scale illegal fishery to emerge very rapidly. By 2005, the scale of the fishery was remarkable: a fleet of 30 purpose built vessels existed, harvesting 1000–2000 tons of abalone with an export value of 35–70 million USD per year. The uncontrolled fishing effort had a dramatic effect on the stock: the average size of abalone decreased significantly, densities declined in the sampling areas, but recruitment of young abalone was still observed at the heavily fished Cape Recife site. It is concluded that the illegal fishing operations and the resultant ecological effects on the abalone resource, reflect deficiencies in South Africa's current abalone fisheries management and compliance paradigm.

Impact of the Treasure oil spill on African penguins Spheniscus demersus at Dassen Island: case study of a rescue operation

The bulk ore carrier MV Treasure sank between Robben and Dassen islands off western South Africa in June 2000. Although releasing less oil than the Apollo Sea spill six years earlier, the number of African penguins Spheniscus demersus oiled (approximately 19 000) in the Treasure spill was almost double the number oiled in the Apollo Sea incident. The majority of oiled penguins was collected from Robben Island. The capture, stabilisation and transport of oiled penguins following the Treasure spill were substantially more successful than during the Apollo Sea rescue operation and resulted in an increase in the percentage of oiled penguins that were released back to the wild. In addition to the 19 000 oiled penguins that were caught, 19 500 un-oiled birds (12 345 from Dassen Island) were evacuated to Cape Recife, 800 km to the east, to prevent them from becoming contaminated. The evacuated birds returned rapidly to Dassen Island and many resumed breeding soon after their return. The restoration success (proportion of birds observed at Dassen Island that were recorded breeding) was substantially greater for evacuated birds than for de-oiled birds. Lightly oiled birds that were released without being cleaned had lower survival rates and were less successfully restored into the breeding population than de-oiled birds, especially if more than 5% of their body was covered in oil. Reproduction exerted a greater cost to de-oiled birds than to evacuated birds. A total of 1 787 orphaned chicks was hand-reared at two separate facilities on the mainland and were released at Robben and Dassen islands. The chicks did not necessarily return to the colony at which they were released. The survival rates and restoration success of chicks reared at the two facilities differed, probably as a result of one group being overfed. Despite the death of about 2 000 African penguins in the Treasure spill, and the substantial disturbance that resulted from the rescue operation, the penguin colonies at Robben and Dassen islands increased by 18% and 26% respectively in the year following the spill. This increase was attributed to a significant increase in the biomass of anchovy Engraulis encrasicolus and sardine Sardinops sagax in 2001. These findings highlight the importance of preventing oil spills in the first place, and in the event of a large oil spill, the conservation value of evacuating un-oiled penguins to minimise their risk of becoming contaminated.

Status, biometrics, moult and possible relationships of the South African population of Roseate Tern

The breeding population of Roseate Terns in southern Africa was estimated to be 250–260 pairs in 2000. Adult birds caught during nocturnal tern roost mist-netting on Bird Island and at Cape Recife, both in Algoa Bay, were closest to their North Atlantic counterparts in wing, bill, total head length, tail and mass measurements. Adult moult differs from that of other populations. The two series wing moult of adults begins in the austral winter and lasts through summer; three feather series may be present in the primary remiges of immature birds. Evidence at present points to reproductive isolation of the South African population and to a degree of migratory behaviour, the extent of which remains unknown. However, size, breeding periodicity and low inter-annual return rate of ringed adults in successive seasons suggests a possible link with the southern Madagascan population.

Redescription of Alebion Carchariae Kroyer, 1863 (Copepoda, Siphonostomatoida) From Isurus Oxyrhinchus in South Africa

AbstractTwo species of the genus Alebion have been recorded from sharks off the coast of southern Africa. The specimens were not fully described. The present work describes Alebion carchariae taken from Isurus oxyrhinchus taken near Cape Recife, South Africa. The new specimens bears some resemblance to the original description of Alebion carchariae and Alebion crassus, but differs from them significantly in especially the morphology of the genital segment.

Occurrence of piscine parasitic copepods (Crustacea) on sharks taken mainly off Cape Recife, South Africa

A total of 10 species of parasitic Copepoda, Alebion carchariae, Perissopus oblongatus, Dinemoura latifolia, Echthrogaleus denticulatus, Echthrogaleus coleoptratus, Pandarus bicolor, Pandarus smithi, Pandarus floridanus, Anthosoma crassum and Nemesis lamna, is recorded together with preferred sites of attachment to the host, from eight shark species, Carcharias taurus, Carcharodon carcharias, Mustelus musteius, Squalus megalops, hunts oxyrinchus, Hexanchus griseus, Galeorhinus galeus and Pliotrema warreni from off the South-Eastern Cape, South Africa. All of the occurrences reported here are new distribution records and in most cases represent new host records for coastal fish of the African continent.

Abundance and Distribution Patterns of Three Temperate Marine Reef Fish (Teleostei: Sparidae) in Exploited and Unexploited Areas Off the Southern Cape Coast

(1) Visual underwater census was used to determine the abundance and size structure of three conspicuous marine reef fish species, on the south-east Cape coast in 1984-86. Sites inside the Tsitsikamma Coastal National Park and outside the reserve at Cape Recife were compared to evaluate the effectiveness of the reserve as a management option for the fish. (2) Three sparids were studied: Chrysoblephus laticeps Cuvier, C. cristiceps Cuvier and Petrus rupestris Valenciennes. (3) Transect techniques suggested that point counts were best suited for mobile species and line counts best suited for more sedentary species that could hide within the reef. (4) Distribution within an area was correlated with depth and substratum relief, both factors reflecting feeding and habitat preferences of the fish. Fewer fish were found in shallow water and on flat reefs. (5) During cold upwelling, fish moved away from the study area, presumably following warmer water. Seasonal differences were observed in the abundance of C. laticeps; abundance was greatest in summer. (6) Sampling showed that the fish were significantly more abundant within the reserve, that there were more of the larger size-classes offish and that the maximum size offish was greater than outside the reserve. (7) The data suggested that the reserve is providing effective protection for species vulnerable to line-fishing.

WADERS (CHARADRII) AND OTHER SHOREBIRDS AT CAPE RECIFE, ALGOA BAY, SOUTH AFRICA: SEASONALITY, TRENDS, CONSERVATION, AND RELIABILITY OF SURVEYS

Summary Spearpoint, J. A., Every, B. & Underhill, L. G. 1988. Waders (Charadrii) and other shorebirds at Cape Recife, Algoa Bay, South Africa: seasonality, trends, conservation, and reliability of surveys. Ostrich 59: 166–177. A total of 126 surveys of waders (Charadrii) and other shorebirds were made along 4 km of shore northwest of Cape Recife. The surveys were conducted bv two observers who counted independently of each other. The variability between observers was least for conspicuous species such as Whitefronted Plover, Blacksmith Plover, African Black Oystercatcher, Whimbrel and Grey Plover, but greatest for cryptic species such as Ringed Plover and for species which formed a minority in mixed flocks such as Curlew Sandpiper and Little Stint. Variability of surveys within years and between years is also considered. Turnstones and Sanderlings were the most abundant waders in summer. Of the Palaearctic waders, Turnstones, Grey Plovers, Sanderlings, Greenshanks and Whimbrels overwintered. In contrast, ...