Intra-archipelago moult dispersion of southern elephant seals at the Prince Edward Islands,southern Indian Ocean

During three summer surveys at Prince Edward Island (PEI), southern Indian Ocean (2001, 2004 and 2008), 416 southern elephant seals Mirounga leonina were inspected for identification tags. In all, 42 seals that had been tagged as weaned pups at their natal site were found on Marion Island (MI), 38 of which could be individually identified by resighting their tag numbers. The majority of the MI-tagged seals were yearlings or subadults, and all but one were hauled out at PEI for the annual moult. The attendance rate of the known individuals at their natal island during the annual moult was only 40%, based on their resighting histories. This was significantly lower than the 77 ± 6% moult attendance rate estimated for a random MI population sample drawn from the same cohorts (based on 10 000 replications). Annual resight probabilities (considering all haulout phases) was 58% per annum for the MI seals seen at PEI, and 80 ± 4% for the simulation. Seasonal and annual absences of seals from MI violate the ‘homogeneity of capture’ assumption of mark-recapture models. When multiple sightings during any year are treated as a single sighting, resights during other haulouts (e.g. breeding) compensate only partially for absences during the moult. Therefore, mark-recapture studies undertaken in archipelagos should ideally include both marking and resighting of individuals on all islands which will allow discrimination between mortality and local migration.     

Monthly mean sea level variability along the west coast of southern Africa

Principal components analysis was used to examine monthly data on sea level obtained from tide-gauge records from the west coast of southern Africa over the period 1957—1975. After a simple correction had removed the effect of local atmospheric pressure, this statistical analysis revealed the structure of nearshore ocean variability over time periods of months to years. The first principal component, accounting for over 55 per cent of the variability in monthly mean sea level, was a near uniform rise and fall everywhere along the west coast of southern Africa. The spectrum of this large-scale structure showed a strong interannual trend, which correlated well with long-term trends of temperature anomaly over the entire South-East Atlantic, and a high-frequency term, which could not be resolved at a time period of one month. The second principal component showed the contrasting response of the northern and southern sites on a seasonal scale, and it could be correlated with seasonal wind data. These results compared well with similar analysis carried out in the North Pacific Ocean.     

Review of the current distribution of southern elephant seals in the eastern South Pacific

The eastern South Pacific southern elephant seal population was extinguished by extensive hunting and the current presence of this species in this area is not well understood. We reviewed existing records from the 1900s to 2014 in the eastern South Pacific, as well as tagged seals and movement records in order to assess the potential immigration source of these individuals. A total of 409 confirmed sightings were compiled, ranging from the southern tip of South America (Cape Horn Archipelago) as far north as Ecuador, including some oceanic island groups. The evidence shows also that recolonisation of its former Pacific distribution has started, with slow population growth in three incipient pupping sites in southern Chile (south of 51°S). Although the source of all of the individuals in the growing colonies is unknown, evidence from tags and satellite tagging indicates that some seals come from subpopulations on the Peninsula Valdes and the Falkland/Malvinas Islands, although mtDNA analysis showed, preliminarily, a greater genetic relationship only with the Falkland/Malvinas Islands rookery.     

Seabirds as consumers in the southern Benguela region

Estimates of consumption of fish by breeding seabirds in the southern Benguela region converge on 50–60 × 10³ tons of food per year. Total annual avian consumption of food is approximately 15,5 × 10⁴ tons, 74 per cent being taken by species which feed on pelagic prey and most of the rest by species which frequently feed on offal at demersal trawlers. Avian consumption is similar in magnitude to that of Cape fur seals and to the catch of the commercial fishery in the southern Benguela region, but far less than consumption by snoek, squid, and, probably, sharks and jellyfish.     

Summer survey of fur seals at Prince Edward Island,southern Indian Ocean

The onshore distributions and the abundances of Antarctic fur seals Arctocephalus gazella and Subantarctic fur seals A. tropicalis were determined at Prince Edward Island during 16-20 December 2008. This repeats a survey conducted in December 2001 and extends the area surveyed to include the entire south-west coast of Prince Edward Island. Of the two colonies of Antarctic fur seals, the colony among Subantarctic fur seals north of Boggel Beach remained small, with increased numbers of Subantarctic fur seals and putative hybrids. The other Antarctic fur seal breeding colony at Penguin Beach remained free of Subantarctic fur seals and had expanded at a mean intrinsic rate of natural increase of 11.4% per year from 2001. With an estimated 810 pups, the Antarctic fur seal is still in the rapid recolonisation phase of population growth. The distribution of the more widespread and abundant Subantarctic fur seals also had increased, with several new breeding colonies along the east coast and one at Kent Crater on the west coast. The annual pup production was conservatively estimated at 14 130 pups. The mean intrinsic rate of natural increase has declined to ?0.3% per year over the last seven years, compared to the 9.3% per year between 1987/1988 and 2001/2002, and the population is in the mature phase of population growth.     

Diet of the South African fur seal (1974–1985) and an assessment of competition with fisheries in southern Africa

Almost 1 000 South African fur seals Arctocephalus pusillus pusillus were collected at sea (inshore and offshore) for examination of stomach contents and other biological parameters. The main prey of seals above the age of one year was teleost fish, of which at least 28 species were identified. Overall, 74,6 per cent of the diet was teleost fish, 16,7 per cent cephalopods, 4,8 per cent crustaceans such as shrimps, prawns, amphipods and isopods and 3,2 percent rock lobster. Within this overall dietary pattern there were marked regional differences. The importance of individual fish species in the diet was investigated from the numbers and the sizes of otoliths occurring in the stomachs, from which the identity and size classes of the prey species could be calculated. Again there were regional differences in the importance of different prey species. On the west coast of South Africa the most important species were anchovy and Cape hakes (each 23% of total diet), whereas on the south coast the important species were anchovy (17%), horse mackerel (14%), pilchard (12%) and Cape hake (14%). Off South West Africa the two dominant species were pelagic goby (52%) and horse mackerel (23%), anchovy and Cape hake constituting only 4 and 5 per cent respectively of total diet. The total annual consumption of anchovy and Cape hake by seals in South African waters was calculated at 125 000 and 120 000 tons respectively.     

Distribution,population size and conservation of the Cape gannet Morus capensis

The Cape gannet is endemic to the southern African coast where it currently breeds at six islands: Mercury, Ichaboe and Possession off South West Africa and Bird (Lambert's Bay), Malgas and Bird (Algoa Bay) off South Africa. Previously, breeding also occurred at Hollams Bird, Halifax and Seal (False Bay) Islands. Equivocal records for Marcus, Dassen and Dyer Islands are not accepted. Off South West Africa, gannets were breeding at Hollams Bird, Mercury and Ichaboe Islands at least as early as 1828, but they only occupied Halifax and Possession Islands sometime between that date and c. 1885, possibly as a result of displacement of gannets from Ichaboe Island during exploitation of accumulated guano deposits in the early 1840s. Gannets bred at Hollams Bird Island until at least 1938, but had ceased breeding at Halifax Island by 1928. Off South Africa the earliest records of breeding are 1648, 1687, 1755 and 1912 for Malgas, Seal (False Bay), Bird (Port Elizabeth) and Bird (Lambert's Bay) Islands respectively. Gannets have not been reported at Seal Island since the late 17th century. On the west coast of Africa the Cape gannet is a regular nonbreeding winter visitor as far north as 4°20′N 6°00′E, but west of 6°E it is rare. On the east coast of Africa it is a common winter visitor as far north as Delagoa Bay, but farther north it is rare. Within its normal range the Cape gannet seldom occurs farther off shore than 100 km; it hardly ever moves inland. Aerial censuses of Cape gannets at breeding islands in 1967, 1969, 1978, 1980 and 1981 are compared with an aerial census conducted in 1956 and other published estimates of abundance. Between 1956 and 1980 the estimated number of breeding pairs at all colonies decreased from c. 150 000 to c. 80 000 and numbers decreased at all three extant gannetries off South West Africa. These decreases are attributed to a greatly diminished food resource following the collapse of the South West African pilchard stock after the late 1960s. The number of gannets decreased at Bird (Lambert's Bay) and Malgas Islands between 1956 and the late 1960s but subsequently increased, trends that are related to performances of the Western Cape pilchard and anchovy resources respectively. At Bird Island (Algoa Bay) gannets were up to 3,5 times more abundant in the late 1970s than in 1956. Other marine resources located east of Cape Point have shown similar large increases in recent years. Rates of increase of gannets at islands off South Africa during the 1970s would have required an unrealistically high survival for the first year had other population parameters remained constant. It is possible that birds emigrated from the South West African Islands. Few gannets have been reported oiled, and conservation of the species seems to be mainly affected by greatly reduced prey availability and injudicious guano harvesting. Human exploitation of juvenile gannets off the West African coast is difficult to assess.     

Population Numbers of Fur Seals at Prince Edward Island,Southern Ocean

During the period 17–22 December 2001, the onshore distribution and the abundance of Antarctic fur seals Arctocephalus gazella and Subantarctic fur seals A. tropicalis were determined for Prince Edward Island. Two breeding colonies of Antarctic fur seals were located on the south-east coast of the island; the first a mixed (with Subantarctic fur seals) breeding colony with an estimated 24 pups on a vegetated promontory on the northern section of Boggel Beach, and the second, a presumably pure Antarctic fur seal breeding colony with an estimated 380 pups, at Penguin Beach. At a mean intrinsic rate of natural increase of 16.2% per year, Antarctic fur seals appear to be in the rapid recolonization phase of population growth. Breeding colonies of Subantarctic fur seals, largely found on the entire east coast, produced an estimated 15 000 pups, and the population had maintained a mean intrinsic rate of natural increase of some 9.5% per year since 1987/88.     

Estimates of phytoplankton and bacterial biomass and production in the northern and southern Benguela ecosystems

Available data on phytoplankton and bacterial abundance and production off the coasts of southern Africa (to the 500 m depth contour) have been assembled and analysed for a network analysis of carbon flow in the Benguela ecosystem. Phytoplankton carbon biomass (from measurements of chlorophyll a) in the northern Benguela (2 558 300 tons) was considerably higher than in the southern Benguela (671 420 and 516 400 tons for the West and South coasts respectively). However, overall annual production (from C¹⁴-uptake measurements) was similar, 77 416 608, 76 399 973 and 78 988 020 tons C·year^?1 respectively. Phytoplankton respiration and sedimentation losses were calculated as functions of primary production and therefore followed similar trends. From the most conservative estimates (mean bacterial biomass of 10 mg C·m^?3 and average P:B of 0,2·day^?1) bacterial biomass is 2–7 per cent of phytoplankton biomass in the northern and southern Benguela, and bacterial production is 3–5 per cent of primary production. Assuming a net growth yield of 30 per cent, bacteria would need to consume 9–15 per cent of the total primary production in order to meet their requirements for carbon consumption. Calculations based on a mean bacterial biomass of 40 mg C·m^?3 and a mean growth rate of 0,5·day^?1 in the upper 30 m of the water column show bacterial biomass to be 8–27 per cent of phytoplankton biomass and bacterial production to be 26–44 per cent of phytoplankton production. Bacterial carbon consumption requirements at these rates amount to 86–147 per cent of total primary production.     

Composition,species richness and similarity of ichthyofaunas in eelgrass Zostera capensis beds of southern Africa

This study collates published and unpublished data on the ichthyofaunas associated with beds of eelgrass Zostera capensis in eight estuaries and one lagoon in southern Africa. These macrophyte beds are utilized predominantly by small teleosts, both species which breed in the estuary and juvenile marine fish. By far the most abundant of the 97 species of fish recorded in these beds were Atherina breviceps, Gilchristella aestuaria, Liza dumerilii, Liza richardsonii and Rhabdosargus holubi. Classification grouped the ichthyofaunas of the six warm-temperate estuaries in the South-Eastern and Southern Cape at a similarity level >50 per cent. Ordination produced a similar clustering and also demonstrated that the subtropical Richards Bay and warm-temperate Mngazana estuary, together with the cold-temperate Langebaan Lagoon, were outliers. Classification and ordination showed that, within an estuary, the ichthyofaunas of dense and sparse Zostera areas were more similar than either was with those of non-vegetated areas. The species richness (R) of fish within eelgrass habitats along the southern African coast tended to decrease from north-east to south-west, a trend attributable to an attenuation in the number of tropical/subtropical Indo-Pacific species. The numerically dominant fish families in eelgrass beds in South Africa showed a greater degree of overlap with those of south-eastern Australia than with those of either southern Japan or eastern North America.     

Summer incidence of humpback whales on the west coast of South Africa

A total of 14 sightings of 25 humpback whales was recorded from temperate waters of the west coast of South Africa in summer (December–February). In addition, a 6,45 m individual (estimated age 6½ months) stranded at St Helena Bay in February 1982, and a 6,15 m individual (estimated age 4½ months) was found ensnared in the buoy line of a lobster trap off Saldanha Bay in December 1990. These records suggest that certain individuals, particularly juveniles, may not undertake the summer feeding migration. Although the 6,45 m individual was emaciated when stranded, the 6,15 m individual had been feeding on stomatopods, indicating that some individuals feed opportunistically during the summer off the west coast of South Africa.     

Survival estimates for the greater crested tern Thalasseus bergii in southern Africa

The nominate race of the greater crested tern Thalasseus bergii breeds only along the coast of the Benguela region (west coast) of southern Africa, where its population is increasing, in contrast to other species of breeding seabirds in the region which similarly depend on forage fish. Although this population’s trends are well known, its demographic parameters remain obscure. We used multi-event capture–recapture–recovery modelling to provide the first estimates of survival. The survival rate of birds older than two years was 0.93 (0.91–0.95); second-year survival was 0.93 (0.90–0.95) and first-year survival was 0.80 (0.73–0.85). A resighting of a 34-year-old bird is a new longevity record for the species. Population growth rates projected with a Leslie matrix model that included our survival estimates were very similar to estimates from annual counts of the breeding population (7–8% y^?1), suggesting that these survival estimates adequately describe the species’ demography. High survival rates have likely contributed to the species’ recent population increase in the region.     

Dynamics of water exchange and salt flux in the Macuse Estuary,central Mozambique,southern Africa

The Siberian subspecies of the red knot Calidris canutus canutus spends the non-breeding season largely in West Africa (Mauritania and Guinea Bissau), where approximately half a million occurred in the 1980s. It was a rarely seen in southern Africa in the early part of the 20th century, but there were about 12 500 in the 1970s and 1980s. The main sites were Langebaan Lagoon, Berg River Estuary, Olifants River Estuary (South Africa) and Walvis Bay Lagoon (Namibia). There was a decline in the number of red knots at Langebaan Lagoon in the 1990s, to around 20% of the number that occurred there in the 1980s. Numbers remained low in the 2000s. In addition, the percentage that remained during the austral winter (the breeding season in the Arctic) declined, and there was none during the period 2001–2009. This suggested that first-year birds, which largely comprise the austral winter population, were no longer travelling to southern Africa. The decline in numbers coincided with the decline in West Africa, but it was disproportionately larger in southern Africa. The observed pattern of change is consistent with a buffer effect, whereby southern Africa represents an extension to the range to less suitable habitat (requiring a 6 000 km extension to the migration) when the population size and competition is high in the main localities in West Africa. We are probably now witnessing the gradual decline in the number of adult birds who are fixed in their use of southern Africa as their non-breeding quarters.     

Assessing the competitive effects of marine mammal predation on commercial fisheries

Commercial fishermen in many parts of the world perceive marine mammals as competitors for a scarce resource: fish. The importance of predation by marine mammals can be evaluated crudely by considering the marine mammal as a rival fishery whose operation is constrained by physiology and energetic requirements, rather than by catch limits and gear restrictions. Evidence collected from grey seals Halichoerus grypus in the United Kingdom, southern elephant seals Mirounga leonina and beluga whales Delphinapterus leucas shows that published information on distribution, based on the location of breeding sites and sightings in shallow water, may give an unrealistic picture of foraging distribution. Studies of diet and distribution can give an impression of the static nature of the inter-action between a marine mammal and the fishery. However, it is the dynamics of the interaction which are important. A critical question to be posed is how will the consumption of a particular prey species vary with its availability to the predator?     

The dynamics of grey seals (Halichoerus grypus) off Amrum in the south-eastern North Sea — evidence of an open population

Grey seals (Halichoerus grypus) have been extinct in the south-eastern North Sea for centuries. Only in recent decades have they re-established a few colonies, the first of which was located on a group of sand bars off the German island of Amrum. Based on frequent counts from aircraft and boats in 1976–2000, and a photo-identification program in 1997, we investigated seasonal dynamics, trends in abundance, pup production, and pup survival in this population. Numbers of hauled-out seals were highest in spring, with a peak of 70–100 in late March or early April, and usually lower than 40 from late May to late January, including the winter breeding season. Both spring and summer counts indicated an average increase of 4–5% per year. Annual pup production was 3–10 in 1988–1995 and 9–13 in 1996–1999, suggesting a breeding stock of only about half the minimum total population size, i.e. 137 individually recognised seals in 1997. The estimated survival of pups until weaning seemed high enough to support autochthonous increase, and hence suggested a self-sustaining breeding stock at least until the late 1990s. Pup survival declined, however, from 95–100% in 1988–1991 to 60–70% in 1992–1999, probably due to erosion of the sand bars. From (i) the relative excess of hauled-out seals in spring, as compared to the phenology of stocks in the western North Sea, (ii) turnover and net loss of individuals during the spring and summer of 1997, as indicated by photo-ID records, and (iii) the low apparent per capita birth rate, we suggest that grey seals off Amrum split into a resident breeding stock and a similar or higher number of seals immigrating outside the breeding season. The latter may originate from larger colonies in the southern and western North Sea, and return there for breeding. In the future, grey seals currently breeding off Amrum may eventually leave the area because of deteriorating conditions. However, a decline of numbers occurring in spring and summer would not necessarily be expected, because seasonal influx from increasing stocks elsewhere in the North Sea is likely to continue.     

Characteristics of coastal trapped waves along the southern and eastern coasts of Australia

The spatial structures and propagation characteristics of coastal trapped waves (CTWs) along the southern and eastern coasts of Australia are investigated using observed daily mean sea level data and results from a high-resolution ocean general circulation model (OGCM), and by conducting sensitivity studies with idealized numerical models. The results obtained from the sea level observations show that shortterm variations, with a typical period of 1 to 2 weeks, dominate the sea level variability in the southern half of Australia. The signal propagates anticlockwise around Australia with a propagation speed of 4.5 m/s or faster in the western and southern coasts and 2.1 to 3.6 m/s in the eastern coast. Strong seasonality of the wave activity, with large amplitude during austral winter, is also observed. It turns out that the waves are mainly generated by synoptic weather disturbances in the southwestern and southeastern regions. The numerical experiment with idealized wind forcing and realistic topography confirms that the propagating signals have characteristics of the CTW both in the southern and eastern coasts. Sensitivity experiments demonstrate that the difference in the phase speed between the coasts and reduction of the amplitude of the waves in the eastern coast are attributed to the different shape of the continental shelf in each region. The structures and the propagation characteristics of the CTWs around Australia are well reproduced in OFES (OGCM for the Earth Simulator) with dominant contribution from the first mode, although meso-scale eddies may modify the structure of the CTWs in the eastern coast. It is also found that generation or reinforcement of the waves by the wind forcing in the southern part of the eastern coast is necessary to obtain realistically large amplitude of the CTWs in the eastern coast.     

Prioritising range-wide scientific monitoring of the Cape fur seal in southern Africa

The range of the Cape fur seal Arctocephalus pusillus pusillus population largely coincides with the region of the cold, nutrient-rich Benguela Current Large Marine Ecosystem (BCLME) adjoining the west coast of South Africa, Namibia and Angola. Range-wide scientific monitoring of the seal population was initiated in the 1970s to inform on population management questions related to commercial seal harvesting and seal–fishery interactions. Since the 1970s, seal-related management goals have changed, especially in South Africa where seal harvesting ceased in 1990 and government has conformed to scientific advice against the culling of seals for the intended benefit of fisheries. However, renewed impetus has been provided to seal research and monitoring through the expansion of the ‘ecosystem-based management’ concept in the region, as well as improved international cooperation in the management of marine resources. Together with wide-scale ecosystem changes in the marine environment, and forecast effects of global climate changes, this has justified the continuation and improvement of range-wide scientific monitoring of Cape fur seals. We prioritised seal monitoring based on cost, effort, and relevance to monitoring objectives that have been identified for the region, with consideration given to the conservation status of top predators, interspecific and predator-fishery interactions and the potential use of Cape fur seals as indicators of ecosystem health. An integrated approach incorporating a suite of life-history attributes of seals is recommended, useful monitoring tools are discussed and the need for coordinated monitoring effort and standardisation of sampling techniques is emphasised.     

The geographic distribution of Echiura from southern Africa

The echiuran fauna of southern Africa currently comprises two families, four genera and 16 species of which one has recently been described as new to science and four are new records for the region. The taxonomic characters distinguishing the genera are given. The zoogeographic distribution of the southern African species is outlined and discussed. Knowledge of the echiuran fauna is too scanty to throw any light on the division of the coastline into faunistic provinces.     

Coastal distribution,movements and site fidelity of right whales Eubalaena australis off South Africa, 1969–1998

Counts and photographs of right whales Eubalaena australis taken on aerial surveys of the southern coast of South Africa between 1969 and 1998 have been used to examine patterns of coastal distribution between successive 20-minute bins of longitude. Some bins had consistently higher densities of whales than others, cither of cows with calves or of unaccompanied adults. Apart from an overall increase in density, the centre of distribution shifted 40–60 minutes of longitude to the west over the 30-year period. Most (>93.4%) female calves born on the South African coast returned there to have their first calf, but only 52.9% were photographed with their first calf in the same or an adjacent bin as that of their natal year. This compares with 60.9% of multigravid females that occurred in the same or an adjacent bin as that of their previous calf, with significantly more west-ward (368) than eastward (255) shifts in distribution between calves. Approximate residence times for cow-calf pairs in the De Hoop region were 12–105 (average = 59.0 ± 3.9) days: dispersal rates were low between July and September but increased thereafter. Incidental records of coastwise movement were mainly to the west, but were probably influenced by the survey direction. Distances moved ranged from 6 to 202 km. at average speeds of 0.08–2.89 km·h^?1. Theodolite tracking of undisturbed groups of right whales from Cape Columbine produced a similar range of swimming speeds. Inter-calf movements of cows between the survey area and the coasts to both east and west indicated that the entire South African coast could be considered as one homogeneous winter assemblage area for right whales.     

Recolonisation of the Robberg Peninsula (Plettenberg Bay,South Africa) by Cape fur seals

The Cape fur seal Arctocephalus pusillus pusillus colony at Robberg Peninsula, Plettenberg Bay, on the south-east coast of South Africa, was driven to extinction by indiscriminate harvesting by the late 1800s. Seals only began to recolonise this site in the 1990s. This study describes the recolonisation process from 2000 to 2009, exploring both within- and between-year count data of seals using the site. Counts increased over the study period from <300 animals to >3 100. Generalised linear models indicated the importance of year and month in explaining variability in the counts. Withinyear variability in the counts decreased over the study period, which may be related to an increasing proportion of resident (as opposed to transient) seals in the colony. However, the colony is currently still in a transition phase with a low ratio of breeding to non-breeding animals, based on the low numbers of pups born in the colony (currently still <100 per year). The influx of seals to the Robberg area may be associated with shifts in prey availability at the ecosystem level. The colony benefits from the protection afforded by the reserve status of the Robberg Peninsula and the existence of a marine protected area adjacent to it. However, human interference associated with fishing and/or ecotourism on the peninsula may inhibit development into a substantial breeding colony. Potential interventions for the conservation and management of this colony are discussed.