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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.
White-breasted cormorants Phalacrocorax [carbo] lucidus breed around South Africa's coast and at inland localities. Along the coasts of the Northern, Western and Eastern Cape provinces, numbers breeding were similar during the periods 1977–1981 (1 116 pairs at 41 localities) and 2008–2012 (1 280 pairs at 41 localities). Along the coast of KwaZulu-Natal (not counted in 1977–1981), 197 pairs bred at nine localities in 2008–2012, when the overall number breeding around South Africa's coastline was about 1 477 pairs. Between the two study periods, numbers decreased in the Northern and Western Cape provinces following the loss of several breeding localities, but they increased in the Eastern Cape. In the Western Cape, however, numbers were stable east of Cape Agulhas and at nine well-monitored West Coast localities that were surveyed from 1978 to 2012. White-breasted cormorants breed throughout the year, with breeding at some localities more seasonal than at others and the timing of peaks in breeding varying at and between localities. In the vicinity of Saldanha Bay/Langebaan Lagoon (Western Cape), in Algoa Bay (Eastern Cape) and in northern KwaZulu-Natal, it is likely that birds moved between breeding localities in different years, although breeding often occurred at the same locality over several years. Human disturbance, presence of predators, competition for breeding space and occurrence of breeding by other waterbirds may influence movements between colonies. Securing sufficient good habitat at which white-breasted cormorants may breed will be important for conservation of the species. The species may breed at an age of 4 years, possibly younger. The bulk of their diet around South Africa's coast consists of inshore marine and estuarine fish species that are not intensively exploited by humans.  相似文献   

3.
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   

4.
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   

5.
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   

6.
The jackass penguin, endemic to southern Africa, is the only member of the Sphenisciformes now breeding in Africa. Its breeding distribution extends from Sylvia Hill, South West Africa (Namibia), to Bird Island, Algoa Bay, South Africa. The non-breeding range extends from Sette Cama, Gabon, to Inhaca Island, Moçambique. Jackass penguins do not usually occur far off shore. The minimum total breeding population in 1978/79 was estimated to be approximately 134 000 birds. Numbers halved between 1956 and 1978 alone as a result of collapses in the South and South West African pilchard populations. Numerical decreases at Possession and Dassen Islands were particularly severe. Prior to 1956 numbers had also decreased, primarily because of large collections of eggs. Sealing activities and guano harvests may also have influenced trends. Only colonies at the periphery of the breeding distribution have increased numerically in recent times, and such increases appear to be related to the availability of suitable prey. Although the species breeds in captivity and is unlikely to become extinct, its continued survival in the wild probably relies on the continued good state of the pelagic fish resources.  相似文献   

7.
The bulk ore carrier Apollo Sea sank south-west of Dassen Island off western South Africa in June 1994, oiling approximately 10 000 African penguins Spheniscus demersus, most of which were collected from Dassen Island. A total of 4 076 de-oiled penguins was released with flipper bands. From 1994 to 2005, follow-up research using re-sighting and capture-mark-recapture methods indicated that about 73% of the de-oiled penguins observed back at Dassen Island attempted to breed, and were thus successfully restored into the breeding population. For de-oiled breeders, the median interval between their first recorded sighting and first recorded breeding attempt was 11 months, indicating a short-term delay in restoration. At least 45% of the de-oiled breeders were still being re-sighted five years after their release, and a minimum of 4% survived into their ninth year. These results represent the most successful restoration estimates anywhere in the world. The proportion of de-oiled juvenile penguins re-sighted back at Dassen Island and recorded breeding was lower than that of birds in adult plumage. De-oiled non-breeders spent significantly more time along the shore and less time within breeding colonies than de-oiled breeders. The mean proportion of de-oiled breeders that abstained from breeding each year during the study period was greater than expected. There was a negative relationship between breeding and subsequent survival and breeding, suggesting a cost of reproduction for de-oiled birds.  相似文献   

8.
Diets of male and female West Coast rock lobster Jasus lalandii in South Africa were compared across a large size range of 10–85 mm carapace length (CL). The diets of male rock lobsters were compared between two different depths, different seasons, across the moult cycle, and among eight sites along the South-Western Cape coast. There was no significant difference in diet between male and female rock lobsters for any of the size-classes examined. Male rock lobsters showed large differences in diet between small and large size-classes. The diet of small lobsters (<75mm CL) consisted of a wide range of species, which included, in order of importance, coralline algae, barnacles Notomegabalanus algicola, sponges and ribbed mussels Aulacomya ater. However, prey items rich in inorganic material were not dominant in their diet, as had been predicted. By contrast, large rock lobsters (>80mm CL) fed on few species, and fish and ribbed mussels were their most abundant prey items. There were some dietary differences between individuals captured at 20 m and those collected at 50 m, but these differences were less marked than between the two sampling sites (the Knol and Olifantsbos). There was seasonal variation in diet at the Dassen Island and Olifantsbos sites. Cannibalism was highest during the moulting periods. Gut fullness varied seasonally at Dassen Island, and was consistently high at Olifantsbos. However, the proportion of the population feeding showed marked seasonal trends at both sites, tracking the commercial catch per unit effort of rock lobster. Ribbed mussels were a ubiquitous and dominant component of the diet at the eight sites sampled. However, south of Dassen Island, black mussels Choromytilus meridionalis were scarce in the diet of rock lobster and sponges predominated. Gut fullness was lowest at the northernmost sites.  相似文献   

9.
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   

10.
On 23 June 2000, the bulk ore carrier MV Treasure sank off western South Africa between Dassen and Robben islands, which individually currently support the largest and 3rd largest colonies of African penguins Spheniscus demersus. Subsequently, more than 19 000 penguins were oiled, almost twice the previous highest number of seabirds oiled during a single event in southern Africa (10 000 penguins after the sinking of the Apollo Sea in June 1994). About 19 000 oiled penguins were collected for cleaning and care and about 150 oiled adults died in the wild. Some 19 500 unoiled penguins were caught at Dassen and Robben islands and relocated to Port Elizabeth, 800 km to the east, to remove them from waters affected by the oil. Of all penguins caught, which amounted to 20% of the total species population, less than 2 000 died within the first month, considerably less than in the Apollo Sea spill. This can be attributed to improved transport of penguins and the rapid arrival at rescue centres of experts able to administer emergency care. However, resources were severely extended and mortality would probably have been considerably higher had large numbers of birds not been removed from the area affected by the oil. Many relocated birds returned to their home islands within a month of being released, but considerable disruption of pair bonds is expected to result from mortality, different periods in captivity and disruption of moult cycles. This is likely to result in decreased breeding success. Recruitment to colonies will also be reduced by substantial loss of chicks and eggs. Although more than 3 000 orphaned chicks were collected for captive rearing, an estimated 4 000 died at the islands before they could be rescued. Up to 20% of bank cormorants Phalacrocorax neglectus at Robben Island, the 3rd largest colony of the species in South Africa, died. There was low success in catching oiled cormorants and in saving those that were caught. Of 53 grown birds of four species of cormorant that were oiled and caught, only 17 survived. Captive rearing of bank cormorant chicks, which it was feared may have been orphaned, proved more successful. Spilt oil had minor impact on gulls, terns and shorebirds in the region.  相似文献   

11.
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   

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.
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.  相似文献   

14.
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   

15.
Cape fur seals Arctocephalus pusillus pusillus were estimated to kill some 6 000 Cape gannet Morus capensis fledglings around Malgas Island in the 2000/01 breeding season, 11 000 in 2003/04 and 10 000 in 2005/06. This amounted to about 29%, 83% and 57% of the overall production of fledglings at the island in these breeding seasons respectively. Preliminary modelling suggests this predation is not sustainable. There was a 25% reduction in the size of the colony, the second largest of only six extant Cape gannet colonies, between 2001/02 and 2005/06. There has been a large increase in predation by Cape fur seals on seabirds around southern African islands since the mid-1980s, coincidental with both an increase in the seal population, altered management of the islands and an altered distribution of prey for gannets and seals. At Malgas Island, most gannet fledglings were killed between 10:00 and 18:00, the period when most are in the water around the island, from mid-January to mid-March, the main fledging period. The Cape gannet is classified as Vulnerable.  相似文献   

16.
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   

17.
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   

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.
African penguins Spheniscus demersus live in the Benguela and western Agulhas ecosystems off southern Africa. Their numbers decreased throughout the 20th century from at least 1.5 million to about 0.18 million adults, although different regional trends were apparent. They feed to a large extent on shoaling epipelagic fish, notably anchovy Engraulis capensis and sardine Sardinops sagax, and regional trends in the abundance of penguins are associated with trends in the abundance and distribution of these prey fish. Many first-time breeders emigrate from colonies where feeding or other conditions at the time are unfavourable to more favourable breeding localities. This has led to both the extinction and formation of colonies. Food now may limit colonies at relatively small sizes, a fact attributable to industrial fisheries reducing the densities of forage fish. African penguins share their habitat with several other predators, with which they compete for food and breeding space. One of these, the Cape fur seal Arctocephalus p. pusillus, increased through the 20th century to 1.5 – 2 million animals at its close. Reported observations of predation by fur seals on seabirds have increased in recent decades and threaten the continued existence of small colonies of penguins. Stochastic modelling suggests that colonies of 10 000 pairs have a 9% probability of extinction in 100 years, so smaller populations should be regarded as "Vulnerable". However, in a period of prolonged food scarcity off southern Namibia, the regional population decreased from more than 40 000 pairs in 1956 to about 1 000 pairs in 2000, and many colonies numbering less than 1 000 pairs became extinct. The minimum viable population for African penguins is currently considered to be >40 000 pairs, likely of the order of 50 000 pairs, a figure equivalent to its level in 2000. The chance of survival of the species through the 21st century is tenuous.  相似文献   

20.
The distributional ranges of Cape anchovy Engraulis encrasicolus and Natal anchovy Stolephorus holodon presently overlap at their eastern and western extremes, respectively, off South Africa’s east coast. These species might become more strongly sympatric as a consequence of changed distributions caused by climate change, possibly leading to intensified interspecific competition for trophic and other resources. A comparative analysis of the trophodynamics of the two species, which set out to assess elements of current niche partitioning between them, was conducted through morphological, dietary and stable-isotope analyses of specimens caught off South Africa’s east coast. Cape anchovy have larger gillraker spacing, gain the majority of their dietary carbon from large (>3 000 µm total length) planktonic crustaceans and occupy a higher trophic level than Natal anchovy, which have smaller gillraker spacing and gain the majority of their dietary carbon from planktonic crustaceans of two size classes (900–1 400 µm and 2 800–3 200 µm total length). These results indicate an element of trophic partitioning between the two species that will mitigate against interspecific competition.  相似文献   

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