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1.
During 2008–2012, the number of crowned cormorants Phalacrocorax coronatus breeding in South Africa was c. 1 900 pairs, compared to 1 700 pairs for 1977–1981. Numbers at 10 islands in the Western Cape province fluctuated around a level of 1 100 pairs from 1991/1992 to 2011/2012, 300 more than from 1978/1979 to 1990/1991. These increases are attributable to the discovery of more colonies and an increased frequency of counting at the 10 islands after 1990/1991. The overall number of crowned cormorants breeding in South Africa is thought stable in the long term. Crowned cormorants feed mainly on small, inshore fish species that are not harvested by humans. Clinidae dominated the diet at 10 colonies adjoining the open sea, whereas Gobiidae contributed most food of birds at three colonies in a lagoon. The stability of the crowned cormorant population contrasts with decreases of some other seabirds endemic to southern Africa that feed primarily on prey that is exploited by fisheries. The crowned cormorant population decreased in the Northern Cape and small numbers initiated breeding at colonies to the east of Cape Agulhas at the turn of the century, but most of the population continues to breed to the west of Cape Agulhas. In some instances the availability of suitable breeding habitat may limit numbers breeding.  相似文献   

2.
Numbers of Cape cormorants Phalacrocorax capensis breeding in South Africa decreased by nearly 50% from approximately 107 000 pairs in 1977–1981 to 57 000 pairs in 2010–2014. Although four colonies had >10 000 pairs in 1977–1981, there was just one such colony in 2010–2014. Almost all the decrease occurred after the early 1990s off north-west South Africa, between the Orange River estuary and Dassen Island. South of this, the number breeding in the two periods was stable, with some colonies being formed or growing rapidly in the 2000s. The proportion of South Africa’s Cape cormorants that bred south of Dassen Island increased from 35% in 1977–1981 to 66% in 2010–2014, with the opposite situation observed in the north-west. This matched a shift to the south and east in the distributions of two of the Cape cormorant’s main prey species, anchovy Engraulis encrasicolus and sardine Sardinops sagax. In 2014, an apparent scarcity of prey in the north-west resulted in Cape cormorants attempting to take bait from hooks of fishing lines over an extended period, a behaviour not previously recorded. The number of Cape cormorants breeding in the south may be constrained by the absence of large islands between Dyer Island in the west and Algoa Bay in the east. If so, it may be possible to bolster the southern population through the provision of appropriate breeding habitat, such as platforms, or restricting human disturbance at suitable mainland cliff breeding sites.  相似文献   

3.
Many top predators in the Benguela ecosystem feed on prey species targeted by commercial fisheries. Their roles as indicators of the state of exploited prey resources, as competitors with commercial fisheries for resources, and as susceptible to impact from commercial fishing on those resources are briefly considered. Trends in the occurrence of anchovy Engraulis capensis and pilchard Sardinops ocellatus in the diet of Cape gannets Morus capensis off South Africa's west coast are related significantly to survey estimates of the abundance of these fish species, and they provide useful confirmation of those estimates. In the 1980s, anchovy decreased in the diet of Cape gannets, but pilchard increased. In both the northern and southern portions of the Benguela system, groundfish were thought to eat most (66–73%) of the total quantity of cephalopods and vertebrates consumed by predators and man in the 1980s. South African fur seals Arctocephalus pusillus pusillus, predatory pelagic fish and man removed roughly equal amounts, with squids, seabirds and cetaceans having a smaller impact. In the 1980s, man and seals removed about two million tons live mass more than in 1930. Indices of the rate of natural mortality of anchovy and pilchard attributable to Cape gannets are not related to biomass of the prey species. That for anchovy was high in 1989 when a poor anchovy year-class was formed. Decreased abundance of anchovy led to poor breeding by Cape cormorants Phalacrocorax capensis in 1989 and 1990. A model linking the Cape cormorant population with anchovy is used to explore the impact of possible exploitation strategies for anchovy on Cape cormorants.  相似文献   

4.
Numbers of gentoo penguins Pygoscelis papua and Crozet shags Phalacrocorax [atriceps] melanogenis breeding annually at Marion Island, one of South Africa's Prince Edward Islands in the South-West Indian Ocean, were strongly correlated over 19 split-years from 1994/1995 to 2012/2013. Both species decreased between the mid-1990s and the mid-2000s, exhibited a partial recovery in the late-2000s and then decreased to their lowest recorded levels in 2012/2013. In both instances, the partial recoveries in the late-2000s were associated with improved breeding success. At a colony of gentoo penguins, breeding success was negatively correlated with the date of arrival of adults to breed. Gentoo penguins and Crozet shags are demersal feeders in inshore waters around Marion Island and there is considerable overlap in the composition of their diets. Therefore, trends in their populations may be driven by food availability, which is likely to be influenced by benthic production around the island. We propose that, in South Africa, and based on the current assessment, the Crozet shag, which elsewhere breeds only at the Crozet Islands, is now Critically Endangered, and the more widely ranging gentoo penguin is Endangered.  相似文献   

5.
Roving creel surveys and aerial surveys of shore-angling were undertaken as part of a national investigation into linefishing in South Africa. Shore patrols utilized a random stratified sampling procedure to collect catch-and-effort data, and a questionnaire provided information on fishing effort, angler demographics, economics and attitudes towards current regulations. A total of 1 677 patrols, covering 19 616 km, was conducted between April 1994 and February 1996, during which period 9 523 anglers had their catches checked and 4 490 were interviewed. A further 16 497 km were covered by aerial surveys, when 22 609 anglers were counted. From the aerial surveys, angler densities were highest on the KwaZulu-Natal coast (4.65 anglers·km?1), followed by the Southern Cape coast (2.29 anglers·km?1), the Eastern Cape coast (0.36 anglers·km?1) and the West Coast (0.12 anglers·km?1). Catch rates varied from 1.5 kg·angler?1·day?1 on the Southern Cape coast to 0.45 kg·angler?1·day?1 on the KwaZulu-Natal coast. Total effort was estimated at 3.2×106 angler days·year?1 and the total catch was estimated at 4.5×106 fish·year?1 or 3 000 tons·year?1. Targeted species varied regionally, with elf Pomatomus saltatrix (29%) being the most sought after species on the KwaZulu-Natal coast, kob Argyrosomus japonicus (18%) on the Eastern Cape coast and galjoen Dichistius capensis on the Southern Cape coast (30%) and along the West Coast (50%). The catch composition by mass was dominated by P. saltatrix on the KwaZulu-Natal coast (29%), the Eastern Cape coast (26%), and on the Southern Cape coast (56%) and by white stumpnose Rhabdosargus globiceps (40%) on the West Coast. Although anglers generally supported the regulations currently governing the linefishery, the questionnaire results showed that knowledge and compliance of them was poor. A low level of law enforcement was found, except for in KwaZulu-Natal. Management of the linefishery is discussed in relation to the findings of this study.  相似文献   

6.
Four species of penguin breed regularly at South Africa's Prince Edward Islands: king penguin Aptenodytes patagonicus, gentoo penguin Pygoscelis papua, macaroni penguin Eudyptes chrysolophus and southern rockhopper penguin E. chrysocome. In December 2008, it was estimated that some 65 000 pairs of king penguins were incubating eggs at Marion Island, the larger of the two islands in the group, and 2 000 pairs at Prince Edward Island. At Marion Island from 1987 to 2008, there was no long-term trend in numbers of king penguin chicks that survived to the end of the winter period, but there was considerable fluctuation in chick production in the 1990s. It was roughly estimated that on average 88% of king penguin chicks survived the winter period (from April to September/October). Numbers of gentoo penguins at Marion Island decreased from more than 1 300 pairs in the mid-1990s to fewer than 800 pairs in 2003, and then increased to almost 1 100 pairs in 2008 as breeding success improved. Between 1994/1995 and 2008/2009, numbers of macaroni and southern rockhopper penguins at Marion Island decreased by about 30% and 70% respectively. In 2008/2009, some 290 000 pairs of macaroni penguins bred at this island, mostly in two large colonies where there was a progressive decrease in the density of nests. At both these colonies, decreases in numbers breeding followed outbreaks of disease. Inadequate breeding success has influenced the decreases of macaroni and rockhopper penguins. In 2008/2009, some 42 000 pairs of southern rockhopper penguins bred at Marion Island and 12 000 pairs of macaroni penguins and 38 000 pairs of southern rockhopper penguins at Prince Edward Island.  相似文献   

7.
Once one of the most numerous seabirds of the Benguela upwelling system, the population of Cape cormorants Phalacrocorax capensis has decreased by 60% in the past three decades and the species is listed as Near Threatened. Declines in prey availability and/or abundance brought about by recent changes in the distribution of pelagic fish stocks and industrial purse-seine fishing are hypothesised to be a key driver of seabird population decreases in the southern Benguela. We investigated the foraging behaviour of breeding Cape cormorants by deploying GPS and temperature–depth recorders on 24 breeding adults from three islands off the coast of South Africa, two of them to the north of Cape Point and a third farther south on the western Agulhas Bank. This provided the first measures of foraging dispersal by a cormorant in the Benguela system, and enabled a comparison of foraging behaviour between birds from these islands. Foraging trips of Cape cormorants lasted between 17 min and >7 h, at a maximum distance of between 2 and 58 km away from their colony. Foraging effort was significantly greater for birds from farther north off the West Coast in terms of trip duration, distance travelled, number of dives and time spent flying compared to those from the southernmost island (Dyer), which is probably a response to low prey availability in the north. Coastal reserves that exclude pelagic fishing from inshore feeding grounds around Cape cormorant breeding colonies may result in increased local prey availability, which would benefit Cape cormorant populations.  相似文献   

8.
This study investigated whether the current lateral boundary for estuaries in South Africa, i.e. the estuarine functional zone (EFZ), includes all estuarine habitats. The EFZ covers 173 930 ha in 304 estuaries/outlets nationally. Field surveys and analysis of available aerial images showed that 82 (12 956.70 ha) of these estuaries (26%) had estuarine habitats occurring outside of this boundary. As a result of mapping scale, the National Vegetation Map does not represent habitats that are associated with small estuaries (approximately 50% of South Africa's estuaries). For estuaries in the Western and Eastern Cape provinces, most habitats have been lost due to urban development, whereas in subtropical areas (northern Eastern Cape and KwaZulu-Natal), cultivation has removed estuarine habitat. Although delineation of boundaries can be complicated by landcover changes, the estuarine lateral boundary in Cape estuaries could be identified based on sediment characteristics (moisture content, organic content, electrical conductivity), groundwater characteristics (salinity, conductivity and depth) and plant species. The delineation of the EFZ needs to be consistent, inclusive of all estuarine physical and biological processes, and cost-effective to identify so that it can protect estuarine habitats.  相似文献   

9.
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.  相似文献   

10.
Populations of the African penguin Spheniscus demersus have decreased dramatically over the past century, due in part to competition for food with commercial fisheries, and the species is now endangered as a result. Economic arguments are used to favour fisheries over the needs of penguins, but penguins have direct value to the South African economy thanks to penguin-based tourism at several breeding colonies. We estimated the value of African penguins at the most important tourist site for African penguins: Boulders on the Cape Peninsula, South Africa. As a mainland colony close to Cape Town, Boulders is accessible to large numbers of visitors; gate revenues in 2009/2010 alone were R14.5 million (US$2 million). A zonal travel-cost analysis revealed an average consumer surplus among Cape Town residents of some R20 per visit. Penguin-based tourism thus forms an integral part of the R25 billion Western Cape tourism sector. Given that the future survival of this valuable resource is dependent, among others, on the availability of sufficient prey, competition with South Africa's purse-seine fishing fleet should be limited through management strategies that lessen the potential effects of fishing on prey available at the local scale.  相似文献   

11.
The red seaweed genus Asparagopsis Montagne (Bonnemaisoniales) contains two widely introduced species that are considered notorious seaweed invaders worldwide, Asparagopsis armata and A. taxiformis, both characterised by heteromorphic, diplo-haplontic life histories. To uncover cryptic introductions of Asparagopsis along the South African coastline and identify ‘Falkenbergia’ isolates (i.e. tetrasporophytic life-history phase morphologically identical between species), the mitochon-drial cox2–3 spacer was sequenced from gametophytes of Asparagopsis taxiformis from Scottburgh, KwaZulu-Natal, on the East Coast, Knysna Lagoon on the South Coast and from tetrasporophytes, otherwise unidentifiable to species level, collected from False Bay near Cape Town on the South-West Coast and Tsitsikamma on the South Coast. Only tetrasporophytes of the temperate Asparagopsis armata were encountered from the Cape Peninsula (Cape Town) probably as far east as to Port St Johns, Eastern Cape province. This is considered an introduced species, and was first collected at Kommetjie (Cape Peninsula) in 1935. Gametophytes of the warm-temperate to tropical A. taxiformis were first collected at Reunion Rocks near Durban in 1984; the KwaZulu-Natal material studied here belongs to an Atlantic Mediterranean cryptic lineage. This taxon is an ecological dominant in some intertidal and shallow subtidal areas in northern KwaZulu-Natal, and is thus considered ‘introduced’ and ‘invasive’. In contrast, A. taxiformis gametophytes, collected in Knysna Lagoon in 2008, clustered with individuals of Indo-Pacific lineage 2. The latter is considered a major invasive lineage in the western Mediterranean, but at present is categorised as introduced in South Africa. This study provides molecular evidence of three independent, cryptic introductions in South Africa, one of them probably very recent, and this is discussed with respect to potential vectors responsible for transport.  相似文献   

12.
Pelagic gobies Sufflogobius bibarbatus were numerically the most important prey of jackass penguins Spheniscus demersus. Cape cormorants Phalacrocorax capensis and bank cormorants P. neglectus sampled at islands off the South West African coast during the period 1978–1982. These three seabirds feed on small gobies near the surface and some of them can also dive sufficiently deep to catch larger gobies. Their populations at islands north of Lüderitz, where gobies are abundant, have been increasing. Cape gannets Morus capensis feed only on large gobies that are infrequently at the surface, and the gannet population off South West Africa has shown a large decrease since the collapse of the pilchard Sardinops ocellata resource in the late 1960s and early 1970s. In the intense perennial upwelling system situated between 22 and 27°S gobies are believed to have partially replaced pilchards during the 1970s. Both pilchards and gobies are able to feed on large diatoms of the genera Chaetoceros and Delphineis, which dominated the inshore phytoplankton in the early 1970s when biomass levels of both pilchards and gobies were low.  相似文献   

13.
Knowledge of population distribution and movement is crucial for the conservation and management of shark species occurring in coastal waters. From 1984 to 2009, 641 scalloped hammerheads Sphyrna lewini, 1 342 smooth hammerheads Sphyrna zygaena and 1 352 unspecified hammerheads Sphyrna spp. were tagged and released along the east coast of South Africa, with recapture rates of 1.9%, 1.5%, and 0.7% respectively. Maximum and average distance moved was 629 km and 147.8 km (95% CI = 33.0–262.7 km) for S. lewini and 384 km and 141.8 km (95% CI = 99.1–184.5 km) for S. Zygaena respectively. The majority of sharks (68% S. lewini, 74.1% S. zygaena and 33.5% Spyrna spp.) were tagged in the Transkei region, with the largest number tagged in Port St Johns. Across regions, most tagged sharks were >50–100 cm precaudal length (PCL), except in Transkei where more sharks >100–150 cm PCL were tagged. In the Western Cape, Southern Cape and Eastern Cape, few sharks were tagged during the autumn/winter months, whereas in KwaZulu-Natal and Transkei sharks were tagged throughout the year. Large-scale directional movements observed may have been migrations in response to seasonal sea surface temperature changes. We identify coastal locations in Transkei that are of importance to juvenile and subadult hammerhead populations year-round.  相似文献   

14.
Although the size distribution of larvae and early juveniles of the saury Scomberesox saurus scombroides in continental shelf waters off the Cape Province, South Africa, is consistent with a south-north passive dispersal by known currents, the size of late juveniles and adults increases from north-west to south-east. Occurrence of these stages is highly seasonal: they are found in summer off the Western Cape and mainly from late summer to winter in Algoa Bay in the Eastern Cape, possibly reflecting longitudinal migration. Large numbers of late juveniles and adults are often found downstream of upwelling plumes off the Western Cape when warmer waters lie close inshore. They are sometimes taken in purse-seines in association with adult round herring Etrumeus whiteheadi and pilchard Sardinops ocellatus. Important predators of late juvenile and adult saury are fast-moving, surface-feeding species: yellowfin tuna Thunnus albacares, Cape gannet Morus capensis and Cory's shearwater Calonectris diomedea. Cape gannets consume an estimated 2 277–6 044 tons of saury annually in South African waters. Predator diets provide important time-series of occurrence, abundance and length-frequency distributions of late juvenile and adult saury.  相似文献   

15.
From 1987 to 2005, numbers of African penguins Spheniscus demersus breeding in South Africa's Western Cape Province increased by about 50%. Numbers decreased at the four northernmost colonies in the region: Lambert's Bay and the three colonies in Saldanha Bay, although at Jutten Island the decrease is inferred from an estimate for 1987, derived from interpolation. Numbers also decreased at Geyser Rock and Dyer Island on the South Coast. At five colonies between Saldanha Bay and Dyer Island there were large increases. At a sixth colony in that region, Seal Island, where Cape fur seals Arctocephalus pusillus pusillus limit breeding space, numbers remained stable. At two colonies that were initiated in the early 1980s, Robben Island and Boulders, increases were initially rapid (>20% per annum) and matched growth of the South African stock of sardine Sardinops sagax. Strong growth at Dassen and Vondeling islands, between Robben Island and Saldanha Bay, was observed from about 1996–2002, when there was a large increase in the biomass of pelagic fish off South Africa. Increases at colonies between Saldanha Bay and Boulders slowed after 2002, whereas the colony at Dyer Island stabilised at that time. In 2003, a new colony was initiated east of Dyer Island at De Hoop Nature Reserve. These latter trends followed an eastward shift in the distribution of sardine. Small penguin colonies may act as foci for growth in a period when the distribution of prey is changing. Hence, it is important that they be maintained, especially those that, if lost, would increase the isolation of regional populations. Some of the small colonies are less susceptible to oil spills than colonies in the proximity of harbours, and for that reason also are important.  相似文献   

16.
During November 1978, Cape cormorants Phalacrocorax capensis at Mercury Island, off South West Africa (Namibia), consumed practically exclusively pelagic gobies Sufflogobius bibarbalus. The mean number of fish per regurgitation was 52 with a mean caudal length of 48 mm and an estimated mean mass of 1.7 g. The estimated mean original mass of stomach contents was 75 g. These Cape cormorants took significantly smaller pelagic gobies than did bank cormorants P. neglectus sampled concurrently at the same locality.  相似文献   

17.
The annual movement of South African sardine Sardinops sagax up the east coast of South Africa, known as the ‘sardine run’, was investigated using data from aerial surveys for the period 1988–2005 and compared with remotely sensed sea surface temperature (SST) and chlorophyll a data. Sardine sighting rates were highest within the Waterfall Bluff Bight off the Eastern Cape Coast, where conditions appeared to be most favourable. Sardine and predator sightings decreased significantly northwards of Mdoni on the KwaZulu-Natal (KZN) coast, whereas the proportion of nearshore sightings increased. The causal mechanism for this inshore concentration is suggested to be the influx of warm Agulhas Current water from the Durban Eddy that forces sardine shoreward. Cape gannet Morus capensis, common dolphin Delphinus capensis and sardine distributions were associated, and there was an association between SST and sardine and predator distributions. There was a marked increase in bottlenose dolphin Tursiops aduncus sightings upon commencement of the sardine run, with these dolphins being consid-ered to be a ‘migratory’ stock that enters KZN waters every winter.  相似文献   

18.
This paper reports on growth of the Boulders colony of African penguins Spheniscus demersus from inception in 1985 to the present. More than 900 pairs now breed there. Growth of the colony slowed in 1995 and 1996 and reversed in 1998, coinciding with periods of low abundance of Cape anchovy Engraulis capensis off South Africa. In December 1996, penguins were excluded from a portion of land where they had formerly bred. They responded by increasing the density of their nests in other areas and expanding their area of breeding longshore. These patterns indicate that food and not space are currently controlling colony growth rate. Much of the colony growth probably results from immigration of first-time breeders from other colonies. Of immigrants, 70–80% may be from Dyer Island to the south-east, where numbers of penguins have decreased. Boulders also is frequently visited by penguins from other colonies, and by rehabilitated birds.  相似文献   

19.
The Ilha dos Tigres of Angola is the only sandy island off the coast of the 2 000km-long Namib Desert and it remains the least known coastal wetland on a desert coast rich in shorebirds. Two surveys of the Baia dos Tigres region in 1999 and 2001 indicated a rich wetland bird diversity consisting of 25 species, with a total of 11 000 birds, at a density of 33 birds km?1 of beach. We established breeding by three species of seabirds — two cormorants and the great white pelican Pelecanus onocrotalus — and confirmed northward range extensions for two of these species. The region supports seven regionally threatened Red Data birds. Several threatened marine turtles occur at the nearby Cunene River mouth, and given the possibility that turtles and other Red Data birds may breed at Ilha dos Tigres, it is recommended that it should become an integral part of the Iona National Park on the adjacent mainland.  相似文献   

20.
Cape fur seals Arctocephalus pusillus pusillus were harvested to extirpation on the Robberg Peninsula, Plettenberg Bay, on the south-east coast of South Africa, between the 17th and early 20th centuries. Seals returned to Robberg in small numbers during the early 1990s and their numbers subsequently increased. We studied the diet of this increasing population using faecal (scat) sampling to determine: the species composition and size of prey in the diet of Cape fur seals at Robberg; to explore temporal variation in the diet; and to investigate the potential for competition between seals and the fisheries around Plettenberg Bay. Of the 445 scats collected, 90% contained hard prey remains and 15 teleost prey species were represented in the 3 127 otoliths that could be identified. The seals’ most important prey species in terms of numerical abundance, frequency of occurrence and mass in the diet, were anchovy Engraulis encrasicolus, sardine Sardinops sagax, horse mackerel Trachurus capensis, sand tongue-fish Cynoglossus capensis and shallow-water hake Merluccius capensis (in decreasing order of importance for numerical abundance). The proportion of anchovy in the diet increased during the study period (2003–2008), whereas the proportion of sardine decreased. The estimated average annual consumption of sardine by seals was higher than the average annual catch made by purse-seine fisheries in this area, suggesting resource competition between seals and purse-seiners, especially in the light of continuing growth of seal numbers in the area. However, direct competition between seals and linefisheries appeared to be minimal. Scat sampling of Cape fur seals holds potential to serve a useful and cost effective indicator of temporal changes in sardine abundance.  相似文献   

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