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Map of the Benguela region, showing place-names mentioned in the text.

Map of the Benguela region, showing place-names mentioned in the text.

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Article
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This review provides a historical overview of human activities in the Benguela and documents their effects on marine animal life. Considered are the activities of conventional industrial and inshore fisheries but also nonfishery activities, such as mariculture, regulation of river flow, introduction of marine invasive species, marine contruction an...

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Context 1
... the purposes of this review the Benguela region ( Figure 1) is defined as extending from Cape Agulhas in the south to the Namibian-Angolan border (17˚S) in the north, a distance of some 2500 km. These boundaries also mark the approximate biogeographical transition zones between the cool-temperate biota of the Benguela and those of the warm-temperate South Coast Province of South Africa to the east and the more subtropical Angolan region to the north ( Emanuel et al. 1992, Branch & Griffiths 1988. ...
Context 2
... a whaling intensity was clearly nonsustainable, and by 1915 catches had crashed to less than 200 ( Figure 4). Thereafter the industry largely switched to other species (blue, fin, and sei whales especially), and by 1963 (when humpback whales were finally given protection by the International Whaling Commission (IWC)) only a handful were being taken annually by the sole surviving land station at Donkergat in Saldanha Bay (Figure 1). Curiously, episodic whaling off Gabon (1934Gabon ( -37, 1949) was reasonably successful, suggesting that the humpback whales passing Saldanha Bay may represent a different component of the population, possibly one feeding to the east of the continent, off Queen Maud Land. ...
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... the period 1844-95 it has proved possible to reconstruct the annual harvest of guano from Namibia (but not from South Africa) using records of guano imported to and exported from several countries (Van Sittert & Crawford 2003). Accurate records of guano harvests are available since 1901 1907 1913 1919 1925 1931 1937 1943 1949 1955 1961 1967 Year Number (10 ) 0 100 200 300 400 500 600 700 1871 1877 1883 1889 1895 1901 1907 1913 1919 1925 1931 1937 1943 1949 1955 1961 1967 Year Number (10 ) 1892 for South Africa and 1896 for Namibia ( Figure 10). The guano harvest was decreased in some years by heavy, unseasonable rains and in others by the periodic scarcity of fish (Hutchinson 1950). ...
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... in 1931, platforms to attract seabirds to breed and to deposit guano were constructed along the coast of northern Namibia between Walvis Bay and Cape Cross. Guano is still collected annually at these platforms ( Figure 10). The main producers of seabird guano in the Benguela system are Cape gannets Morus capensis at six islands and Cape cormorants Phalacrocorax capensis at the platforms and most islands. ...
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... 1956, they bred at Dassen Island, where they were left relatively undisturbed. The population in the Western Cape had been reduced to about 30 pairs between 1930 and 1956, but following cessation of persecution, it increased to 504 pairs in 1993 ( Crawford et al. 1995a) and 603 pairs in 2000 ( Figure 11). ...
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... sources of food have been used especially by great white pelicans, Cape gannets, kelp gulls, Hartlaub's gulls Larus hartlaubii , and some of the nonbreeding visitors to the Benguela system (Ryan & Rose 1985). The populations of great white pelicans and kelp gulls increased in the Western Cape in the past two decades (Figure 11). This was probably a response to the lifting of controls on these populations. ...
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... catches of anchovy off South Africa have been in the region of 230,000 t yr -1 and have varied between 40,000 t in 1996 and 596,000 t in 1987. A time series of pelagic landings by major species is given in Figure 12. ...
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... catch records from this fleet indicate that the sardine catches reported during the 1960s must be regarded as a minimum (Boyer & Hampton 2001). After 1968, the Namibian pelagic fishery experienced a decline in landings to around 625,000 t in 1972, followed by slightly increased catches for a few years, before another abrupt collapse in the early 1980s ( Figure 12). These collapses have been primarily attributed to overfishing, although poor sardine recruitment resulting from adverse environmental conditions exacerbated the decline. ...
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... then catches have rarely exceeded 50,000 t and have declined to zero following the anomalous environmental event recorded in the mid-1990s. Overall, it can be seen that landings by pelagic fisheries in the Benguela ecoregion have fluctuated 10-fold over the period 1950-2001, between 185,000 t and 1.9 million t, with a long- term average of 770,000 t ( Figure 12). Peak landings were made in the decade 1965-75, primarily by the Namibian purse-seine fleet (80% of total pelagic landings in 1968 and 1969). ...
Context 10
... of scale deposits in sediments from upwelling systems suggests that these population fluctuations, or regime shifts as they have become called, are a natural phenomenon that occurred in the absence of fishing ( Schwartzlose et al. 1999). Estimates of anchovy and sardine stock size in the Southern Benguela, derived initially from fishery-dependent data, but more recently from fishery-independent surveys, corroborate the catch data ( Figure 13). Off South Africa, anchovy replaced sardine as the dominant small pelagic species following the collapse of the sardine population. ...
Context 11
... dominance lasted from 1965 until the mid-1980s, after which a steady increase in the sardine population resulted in populations of approximately equal size during the latter half of the past decade. Estimates of Namibian sardine biomass indicate that the stock collapsed from more than 11 million t in 1964 to well below 1 million t by the mid-1970s, and the population has not attained more than 500,000 t since ( Figure 13). Unfortunately, biomass estimates for Namibian anchovy are not available. ...
Context 12
... fishing by Japan and Spain in the early 1960s showed that catch rates were higher off Namibia than off South Africa ( Gordoa et al. 1995). This resulted in the expansion of the fishery into Namibia waters, an increase in the foreign distant-water fleets, and a rapid escalation of hake landings, reaching over 1 million t by 1972 ( Figure 14). This rapid escalation of fishing effort prompted the establishment of the International Com- mission for the Southeast Atlantic Fisheries (ICSEAF) in 1972. ...
Context 13
... the next few years ICSEAF introduced a minimum mesh size of 110 mm, a system of international inspection, and allocated quotas to member countries. South Africa declared a 200-nautical mile exclusive economic zone on November 1, 1977, and excluded all but a small amount of foreign effort, thereby reducing the hake catches off South Africa ( Figure 14). South Africa then embarked on a rebuilding strategy for the Cape hake resource by setting conservative annual catch limits. ...
Context 14
... international fishery off Namibia was managed by ICSEAF until independence in 1990. The newly recognised nation then declared a 200-nautical mile EEZ and excluded all foreign fishing effort, resulting in a dramatic drop in hake catches ( Figure 14). Since 1990 there has been a perceived gradual recovery of the hake resource and an increase in hake catches. ...
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... minimum marketable size for hake was certainly greater in the early days of the fishery than today, resulting in a higher proportion of discards. The "official" hake catch statistics ( Figure 14) prior to 1972 were thus increased by 39% in accordance with a decision made by ICSEAF in 1978(Andrew 1986). In the 1980s the hake fishing industry was forced to develop a market for small hake because of the depleted nature of the resource. ...
Context 16
... quantities of adults are taken in bottom trawls and adults in spawning condition have been observed during research cruises to the west coast. (Note that the horse mackerel landings shown in Figure 14 include catches taken by midwater trawl off the south coast of South Africa.) It is generally assumed that the horse mackerel resource off the west coast of South Africa was a southern extension of the large Namibian resource. ...
Context 17
... species such as white steenbras Lithognathus lithog- nathus, elf Pomatomus saltatrix, kob Argyrosomus inodorus, white stumpnose Rhabdosargus glo- biceps, yellowtail Seriola lalandi and galjoen Dichistius capensis contributed over 90% to the total beach-seine catch at Muizenberg (False Bay) around the turn of the century (Lamberth 1994). The contribution of these species to net catches has, however, decreased substantially since then, and Liza richardsonii made up over 77% of the total mass landed by the period 1977-87 ( Figure 15). Despite legislation introduced in 1974 preventing the targeting of linefish by net fishers, illegal net fishers still land in the region of 150 t yr -1 . ...
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... these are accurate (figures are not rounded off), the recorded catches for a 33-yr period provide a valuable insight into the net fishery in St. Helena Bay at the time. A drastic reduction in annual catches occurred, with an average annual catch prior to 1900 of approximately 102 t (calculated from a conversion ratio of five adults kg -1 and eight juveniles kg -1 ), declining to only 16 t thereafter, a 85% decrease ( Figure 16). It appears likely that the observed decline was due to the high fishing effort by both estuarine and marine net fishers. ...
Context 19
... the decline in the St. Helena Bay catch for this period, the total Liza richardsonii landings for the region as a whole (Figure 17) rose to 1775 t for the period 1927-31 (Marine and Coastal Management, unpublished data), substantially more than the 259-323 t recorded for 1898-1900(Gilchrist 1899, 1900, 1901). The total catch for the period 1974-99 appears to show a sustained decline since 1987-99 ( Figure 17). ...
Context 20
... the decline in the St. Helena Bay catch for this period, the total Liza richardsonii landings for the region as a whole (Figure 17) rose to 1775 t for the period 1927-31 (Marine and Coastal Management, unpublished data), substantially more than the 259-323 t recorded for 1898-1900(Gilchrist 1899, 1900, 1901). The total catch for the period 1974-99 appears to show a sustained decline since 1987-99 ( Figure 17). These data, however, are based on compulsory catch returns by net fishers. ...
Context 21
... catches of the six main target species over three periods for which adequate data are available are shown in Figure 18. Catches in the Western Cape, which are dominated by snoek, have increased dramatically over the past century, whereas those on the Southwestern Cape, which are made up of a more diverse mixture of species, have declined over the same period. ...
Context 22
... catches of snoek can be analysed in a number of ways: in terms of total domestic and foreign catch, capture location, or method of capture. Total annual catches from the Benguela ( Figure 19A) increased markedly from 5000-19,000 t in 1960-77 to 26,000-82,000 t in 1978-90 with the influx of foreign trawlers in 1978, and then dropped again to 12,000-25,000 t following their withdrawal in 1991. The proportion of the catch made in Namibian waters (Northern Benguela) rose commensurately from 10-20% to 40-80% during the period of foreign involvement, and then declined to 5-9% after they were excluded ( Figure 19B). ...
Context 23
... annual catches from the Benguela ( Figure 19A) increased markedly from 5000-19,000 t in 1960-77 to 26,000-82,000 t in 1978-90 with the influx of foreign trawlers in 1978, and then dropped again to 12,000-25,000 t following their withdrawal in 1991. The proportion of the catch made in Namibian waters (Northern Benguela) rose commensurately from 10-20% to 40-80% during the period of foreign involvement, and then declined to 5-9% after they were excluded ( Figure 19B). Looking at the method of capture ( Figure 20), handline catches of snoek in the Southern Benguela during the 20th century, despite high interannual variation, demonstrate some noteworthy trends. ...
Context 24
... stocks have been identified within the Benguela ecosystem: Meob Bay to Cape Frio (Kirchner & Holtzhousen 2001) and Cape Point to Cape Agulhas (Griffiths 1997a). Although annual yield from the Southwestern Cape stock declined by 40% during the 20th century, CPUE dropped by at least 90% (Table 1 and Figure 21). This evidence of severe overexploitation is further supported by an estimated spawner biomass per recruit ratio of as little as 8% of pristine and an instantaneous fishing mortality rate threefold that of natural mortality (Griffiths 1997b). ...
Context 25
... geelbek is a predatory sciaenid that attains a weight of 15 kg and feeds almost exclusively on sardines and anchovy ( Griffiths and Hecht 1995). Once the most important linefish of the South- western Cape (Figure 18), catch rates in this region declined by more than 95% during the 20th century. Although geelbek caught in the Southwestern Cape form part of a single South African stock, similar declines in CPUE throughout its range confirm the severe stock depletion (Griffiths 2000). ...
Context 26
... to the warm-temperate waters of South Africa, this sparid reef fish is the second most important linefish of the Southwestern Cape ( Figure 18). Recent tagging studies suggest that carpenter of the western and central Agulhas Bank comprise a single stock ( Griffiths and Wilke 2002). ...
Context 27
... the commercial fishery for west coast rock lobster, Jasus lalandii, has extended from Sylvia Hill, north of Luderitz, to Cape Hangklip in False Bay (Figure 1). The species occurs over a wide depth range, from intertidal rock pools to a few hundred metres depth, the depth of occurrence extending deeper in the southern than in the central and northern parts of the range. ...
Context 28
... anthropocentric view of rivers, that water running down them to the sea is wasted, has led to overmanipulation for water supply of all west-and southwest-flowing rivers of the subcon- tinent. As a result, rivers that historically contributed to estuarine and inshore coastal processes, especially the Orange-Vaal, the Cape Olifants, the Great Berg, the Palmiet and the Breede (Figure 1), either no longer flow or flow at greatly reduced volumes and in a greatly regulated manner, due to overabstraction and the construction of water supply reservoirs and interbasin water transfer schemes (IBTs). The situation has become so serious that a number of recent Global International Water Assessment (GIWA) workshops have identified human manipulation of water resources and overutilisation as the single most important threat to the ecological functioning of the region ( Prochazka et al. 2001, Davies 2002. ...
Context 29
... samples from unmined areas were compared with samples from areas mined at different times in the past, providing a quasi-time series of recovery after mining. The change in community composition and species diversity was immediate (within 1 month) due to mortality from gravel extraction (Figure 31). This was followed by a period of deterioration (up to 19 months) due to the slow reaction time of the benthos to disturbance. ...
Context 30
... capital invested in inshore fishing more than tripled from £1.1 million in 1944 to £3.7 million by 1947 and was used to modernise vessels, plants and machinery (Skaife 1948). The FDC provided separate capital infusions for housing and boat loans, the former to secure cheap black labour and the latter to create a white boat-owning class in the inshore fisheries (Van Sittert 1992, 2002). ...

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... These papers summarize the work done in the region until this date, and we have drawn extensively on them for the general description of the system. Since then, additional reviews have appeared in a number of outlets, including those by Griffiths et al. (2004), Field and Shillington (2005) and Shannon et al. (2006). ...
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... Fishing methods include demersal and midwater trawling, purse seining and long-lining, plus line fishing for a number of other species (Crawford et al. 1987, Griffiths et al. 2004DAFF 2014). Purse seining is responsible for the largest percentage of the catch We are not considering either handlining or the inshore fishery although these are important socio-economically, especially along the west coast of South Africa (Griffiths et al., 2004). ...
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... Studies in the Benguela upwelling system provide another example of the potential complexity of climate change effects through interaction with other factors (Checkley et al., 2009). In the northern Benguela, populations of sardines (Sardinops sagax) and anchovies (Engraulis encrasicolus) have remained collapsed since their overexploitation, 45 years ago ( Griffiths et al., 2004), threatening species of top predators, such as the community of seabirds specialised on small pelagic fishes (Crawford, 2007). Environmental anomalies involving unusual low oxygen events are thought to have prevented the return of small pelagics (Cury and Shannon, 2004). ...
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Tuna catches represent a major economic and food source in the Pacific Ocean, yet are highly variable. This variability in tuna catches remains poorly explained. The relationships between the distributions of tuna and their forage (micronekton) have been mostly derived from model estimates. Observations of micronekton and other mid-trophic level organisms, and their link to regional oceanography, however are scarce and constitute an important gap in our knowledge and understanding of the dynamics of pelagic ecosystems. To fill this gap, we conducted two multidisciplinary cruises (Nectalis1 and Nectalis2) in the New Caledonian Exclusive Economic Zone (EEZ) at the southeastern edge the Coral Sea, in 2011 to characterize the oceanography of the region during the cool (August) and the hot (December) seasons. The physical and biological environments were described by hydrology, nutrients and phytoplankton size structure and biomass. Zooplankton biomass was estimated from net sampling and acoustics and micronecton was estimated from net sampling, the SEAPODYM ecosystem model, a dedicated echosounder and non-dedicated acoustics. Results demonstrated that New Caledonia is located in an oligotrophic area characterized by low nutrient and low primary production which is dominated by a high percentage of picoplankton cyanobacteria Prochlorococcus (>90%). The area is characterized by a large-scale north-south temperature and salinity gradient. The northern area is influenced by the equatorial Warm Pool and the South Pacific Convergence Zone and is characterized by higher temperature, lower salinity, lower primary production and micronekton biomass. The southern area is influenced by the Tasman Sea and is characterized by cooler temperature, higher salinity, higher primary production and micronekton biomass. Interactions between the dynamic oceanography and the complex topography creates a myriad of mesoscale eddies, inducing patchy structures in the frontal area. During the cool season, a tight coupling existed between the ocean dynamics and primary production, while there was a stronger decoupling during the hot season. There was little difference in the composition of mid-trophic level organisms (zooplankton and micronekton) between the two seasons. This may be due to different turn-over times and delays in the transmission of primary production to upper trophic levels. Examination of various sampling gears for zooplankton and micronekton showed that net biomass estimates and acoustic-derived estimates compared reasonably well. Estimates of micronekton from net observations and the SEAPODYM model were in the same range. The non-dedicated acoustics adequately reproduced trends observed in zooplankton from nets, but the acoustics could not differentiate between zooplankton and micronekton and absolute biomasses could not be calculated. Understanding the impact of mesoscale features on higher trophic levels will require further investigation and patchiness induced by eddies raises the question of how to best sample highly dynamic areas via sea experiments.
... Potential impacts include construction of seawalls, jetties and railway embankments directly into the intertidal zone, as well as a myriad of more subtle human impacts, including: ducting of storm water onto the shore; increased pollution levels; enhanced levels of exploitation of select species for food or sport; trampling; disturbance of avian predators, etc. Many of these impacts are discussed by Griffiths et al. (2004) and Griffiths and Mead (2011), but few have been quantified in the Cape Town region specifically (but see Bally and Griffiths 1989, van Herwerden and Ryan et al. 2009, for studies on impacts of trampling, human utilisation patterns of beaches, and plastic debris, respectively). ...
... Both these reports thus suggest that densification of kelp took place in Hermanus between 1920 and 1939. The establishment of kelp beds in this region would have had profound ecological and economic implications, since kelp is intimately associated with abalone and other economically important species that have subsequently become pivotal to the economy of this region, and is also now commercially exploited as a source of food in abalone culture (Griffiths et al. 2004; Rothman et al. 2006). Indeed, dense kelp beds are thought to change the entire pattern of energy flow in coastal ecosystems in this region (Field and Griffiths 1991). ...
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Repeat photography was used to illustrate long-term changes occurring in coastal habitats in the Western Cape, South Africa. Historic images were sourced from books and theses, the public and subject specialists, and repeat photographs were then taken from the same perspectives. Visible changes could be categorised into four types: (1) changes in species’ ranges; (2) biological invasions; (3) sea level changes; and (4) direct engineering impacts. In terms of range changes, the images depict a progressive easterly spread of the cold-water kelp Ecklonia maxima and parallel easterly contraction of the warmer-water mussel Perna perna, both evidence for declining water temperatures along the South-West Coast. Since c. 1980 most shores have also become conspicuously invaded by the alien Mediterranean mussel Mytilus galloprovincialis, while those on the West Coast have also been visibly invaded by the more-recently introduced Pacific barnacle Balanus glandula. No changes in vertical zonation due to changing sea levels could be detected, despite suitable images being available. Construction along the shore has radically altered the appearance of the shoreline in urban areas. Repeat photography thus proved a useful tool for both detecting and dramatically illustrating historic changes over the past century. These changes have altered substantially both the appearance and ecological attributes of many rocky shores in this region.