Has fishing pressure caused a major shift in the distribution of South African Sardine?

ICES CM 2006/B:11 Has fishing pressure caused a major shift in the distribution of South African Sardine? Janet C Coetzee, Carl D van der Lingen, Tracey Fairweather and Laurence Hutchings A major shift in the distribution of South African sardine (Sardinops sagax) has resulted in a significant mismatch in fishing effort versus fish abundance in recent years. The fishery for sardine started on the west coast during the 1940s, and processing capacity there increased rapidly together with large increases in annual landings to the early 1960s, after which the fishery collapsed due to overfishing. Since the inception of conservative management practices in the 1980s the population has steadily increased, and currently supports catches similar to pre-collapse levels. Since 2001, however, the bulk of the sardine population has been situated on the south coast, far away from processing facilities. Fishing effort has increased substantially on the south coast, particularly during the past three years, reflecting the decline in abundance of sardine on the west coast. Three hypotheses explaining the change in distribution of sardine have been proposed; the first that intensely localized (i.e. west coast) fishing pressure depleted the west coast part (or sub stock) of the population; the second that the shift was environmentally induced following a reduction in productivity on the west coast; and the third that successful south coast spawning and recruit survivorship contributed disproportionately more towards the bulk of recruitment, and that progeny spawned in that region now dominate the population and exhibit natal homing. These first of these hypotheses is evaluated, and management implications of the shift discussed. Keywords: sardine, distribution, spatial dynamics, fishing effort, environment, management, biological indicators Contact author: Janet C. Coetzee: Marine and Coastal Management, Department of Environmental Affairs and Tourism, Private Bag X2, Rogge Bay, 8012, South Africa.[tel: +27 21 4023176, fax: +27 21 4217406, email: jcoetzee@deat.gov.za] Introduction Sardine (Sardinops sagax) is a major component of a valuable commercial pelagic purseseine fishery which has been in operation since the 1940s off the West Coast of South Africa (Crawford 1980). Intensive exploitation during the first years of the fishery led to rapidly increasing annual catches of sardine through the 1950s with a peak at around 400 000 tons in 1962. This unregulated high exploitation level was unsustainable and lead to a subsequent drastic decline in catches and eventual collapse of the fishery by the end of the 1960s. Catches of sardine remained low during most of the 1970s, averaging at around 80 000 tons annually and decreased even further during the 1980s (average of 40 000 tons annually). Following the initiation of a fishery-independent programme of

acoustic surveys to estimate pelagic fish abundance in 1983 (Hampton 1987, 1992; Barange 1999) a stock rebuilding strategy which included setting and enforcement of an annual total allowable catch (TAC) based on the results of these surveys was implemented during the mid 1980s. Subsequent recovery of the sardine stock to levels similar to those estimated prior to exploitation has been attributed to this conservative management policy (Cochrane et al. 1998). Catches of sardine have averaged above 200 000 tons since 2001 following a period of exceptional recruitment between 2001 and 2003. The distribution and movements of South African sardine at different life stages is not well understood but has essentially been assumed to be similar to that of anchovy. for which patterns have been well established (Crawford 1980, 1981; Shelton and Hutchings 1982; Armstrong et al. 1985; Shelton 1986; Hampton 1987; Hutchings et al. 1998). The distributional range of sardine extends from the northern border of South Africa at the Orange River off the west coast to Richard s Bay on the north-east coast (Beckley and van der Lingen 1999). The bulk of the adult biomass has however been confined to the lower west coast and Agulhas Bank area as far east as Port Alfred during most of the period for which we have observations. Adult sardine concentrate predominantly on the western Agulhas Bank (WAB) during their major spawning season in spring and late summer (Crawford 1980; Crawford et al. 1980; Armstrong et al. 1985, 1987, 1988, 1991; Hampton 1987, 1992; Shelton 1986; van der Lingen and Huggett 2003; Miller et al. 2006). Ichthyoplankton is transported west and north towards the west coast nursery ground by a jet current associated with a strong thermal front between cold upwelled water and warm oceanic water flowing northward along the shelf-edge of the Cape coast (Shelton and Hutchings 1982; Nelson and Hutchings 1987; Fowler and Boyd 1998; Miller et al. 2006). A return migration of juveniles southwards along the west coast is initiated during late summer/early autumn, with recruitment to the adult population on the Agulhas Bank occurring during autumn and winter (Hutchings 1992; Hutchings et al. 1998; Barange et al. 1999; Hutchings et al. 2002). While a significant quantity of sardine recruits has also been observed at times on the south coast during annual recruitment surveys conducted during winter (Barange et al. 1999; Beckley and van der Lingen 1999), west coast recruitment remains dominant. A mechanism for south coast recruitment which relies on local retention of eggs and larvae rather than transport to the west coast nursery ground has recently been established (Lett et al. 2006; Miller et al. 2006) and suggests that sardine may be able to optimize their reproductive strategy by selecting between spawning areas (van der Lingen et al. 2001; Miller et al. 2006). Evidence also exists which indicates that sardine are fairly unspecific in selection of their spawning habitat (van der Lingen et al. 2001; Twatwa et al. 2005), which may partly explain the observed pattern in sardine spawning where shifts between west coast spawning and east coast spawning have occurred frequently in the past (van der Lingen et al. 2001) Adult sardine are generally targeted for canning, although some juveniles are caught as by-catch in the anchovy recruitment fishery on the west coast. During the early years of the fishery, most of the fishing effort was concentrated on the west coast (Crawford 1980; Barange et al. 1999) where sardine were abundant for most of the year, resulting in

intensive development of infrastructure related to fish processing centered around the harbour at St. Helena Bay. During the 1960s and 1970s there was an expansion of the fishing ground for sardine southwards and eastwards as far as Cape Agulhas on the WAB (Crawford 1981). More recently there has been an increase in fishing effort further east (van der Lingen et al. 2005; Fairweather et al. 2006a), particularly in the Mossel Bay area, following an observed shift in the distribution of sardine towards the east. The area west of Cape Agulhas (which incorporates the west coast, the southwest coast and the WAB) contained the bulk of the sardine biomass during the 1980 s and early 1990 s (Barange et al. 1999). Although a gradual increase in the proportion of sardine in the area east of Cape Agulhas has been noted since 1995, the majority of sardine were located on the WAB up to 1999, when for the first time since the start of the acoustic survey program sardine biomass east of Cape Agulhas exceeded that to the west. This distribution pattern has persisted since, and has severe cost and logistical implications for the fishery and management of the stock as there is a mismatch between the location of sardine availability and fish processing facilities as well as between fish abundance and fishing effort. Several hypotheses have been suggested which could explain the observed change in the distribution of sardine from the WAB to the central and eastern Agulhas Bank (van der Lingen et al. 2005). These include local depletion of fish stocks on the west coast and WAB following higher levels of exploitation in the west compared to the east, environmentally induced changes in distribution of sardine spawners as a result of optimal spawning habitat selection (van der Lingen 2001), and that successful south coast spawning and recruit survivorship contributed disproportionately more towards the bulk of recruitment, and that progeny spawned in that region now dominate the population and exhibit natal homing. The aim of this paper is to evaluate the first of these hypotheses, which is related to fishing effort and local depletion, with data currently available and to discuss the management implications of the sardine distributional shift. Methods Acoustic and catch data collection Two acoustic surveys have been conducted annually to estimate the biomass and determine the distribution of small pelagic fish species off South Africa since 1984. The total adult biomass is estimated in November each year between Hondeklip Bay and Port Alfred, while recruitment is estimated in May between the Orange River in the north and Port Alfred in the east (see Figure 1). In recent years, survey effort towards the east has increased substantially during both surveys as a result of a more eastward distribution of both sardine and anchovy spawners. The surveys are conducted along a series of prestratified, randomly spaced, parallel transects, designed to obtain unbiased estimates of stock size and sampling variance (Jolly and Hampton 1990; Barange et al. 1999).

Data on the location, mass, and species composition of landed catches is collected by fisheries inspectors and/or monitors at designated landing points along the coast. Commercial catches are sampled at field stations adjacent to factories where the majority of the catch is landed for processing: data on species and size composition and biological characteristics have been collected routinely since 1953. Biological data collected includes measurements of caudal length (CL), mass, sex, gonad mass and macroscopic gonad maturity stage (Fairweather et al. 2006a). Individual landings are assigned a length frequency using the nearest (in space and time) sample length frequency, and catch length frequencies are raised according to their relative contribution to total catch in order to generate monthly and annual Raised Length Frequency (RLF) tables. Spatial analysis of survey and catch data Suggestions that sardine spawning is divided between two recruitment systems, with the west coast and western Agulhas Bank part of a west coast system, and the remaining spawning areas part of an Agulhas Bank system (Lett et al. 2006; Miller et al. 2006) implies that a division of the continental shelf at Cape Agulhas to aid east/west comparisons is plausible (Figure 1). In this context, spatial statistics relating to survey distribution patterns, catch distributions, and biological indicators have been compared between the west coast system and the Agulhas Bank system. In addition, to investigate temporal trends in distribution of sardine catches and distribution, comparisons have been made between earlier years (prior to 2000) and later years (after 2000) as these periods coincide with periods of west coast system and Agulhas Bank system domination, respectively. The surface area occupied by the sardine population during each survey was computed by projecting the contoured density surface onto a plane and calculating the positive area of the projection in squared degrees. The relationship between latitude and distance is constant, whereas that of longitude varies with the cosine of latitude. Conversion of squared degrees to squared nautical miles was therefore according to: 2 A ( nm ) = 60 (60 cos( latitude)), where latitude is the mean latitude of the shelf area, here taken as 35 S. Results The total biomass of sardine increased gradually from under 50 000 tons in 1984 to around 2.5 million tons in 2000 (Figure 2), and whilst consecutive years of very good recruitment pushed the total biomass up to record levels above 4 million tons in 2002, recent poor consecutive recruitments have however led to a decline in adult biomass to around 1 million tons. Composite maps showing the distribution and relative abundance of sardine during periods of different biomass levels (low = 0-33.3 percentile; medium =33.3-66.6 percentile; and high = 66.6-100 percentile) are presented in Figure 3. The importance of the area west of Cape Agulhas, particularly the WAB but at times also further up the west

coast, as a sardine refuge during periods of low biomass is clearly evident, with only low density distributions observed further east (Figure 3a). At medium biomass levels the WAB area remains the preferred area for sardine and the distribution in this region is expanded slightly northward and southward from that observed during periods of low biomass (Figure 3b). The area occupied east of Cape Agulhas is also expanded significantly compared to that at low levels of biomass. At high biomass the WAB remains important, but the area east of Cape Agulhas now supports most of the sardine biomass (Figure 3c). There also seems to be a consistent separation between sardine found west and east of Cape Agulhas, with overlap in this area between the two parts of the population occurring only at very high biomass levels. The increase in the area occupied by sardine at higher biomass is confirmed when calculating the area occupied by sardine as a function of biomass (Figure 4). Whereas the rate of increase was higher at low biomass (less than 1000 000 tons) than at high biomass, more variability in the area occupied at high biomass was evident compared to low biomass. Further investigation into the changes in area occupied by the western and eastern part of the population in relation to the biomass east and west of Agulhas revealed that the relationship between area and biomass was mostly driven by a rapid expansion of the area occupied by the eastern part of the population. Expansion of the area occupied by sardine in the western area was much slower in comparison, and the relationship between area occupied and biomass not as strong as for the area east of Cape Agulhas (Figure 5). When comparing the biomass found east and west of Cape Agulhas (Figure 6) it is evident that the contribution of the biomass west of Cape Agulhas to the total biomass was larger than that of the biomass east of Cape Agulhas up until 1998. In 1999, a large increase in the biomass east of Cape Agulhas relative to that west of Cape Agulhas caused a shift in the distribution of sardine to the Central and Eastern Agulhas Bank. Further increases in the biomass of sardine after 1999 were mainly as a result of increased biomass east of Cape Agulhas, and the importance of the western part of the population diminished. Distribution of fishing effort over the same time period as survey data reveals that as the biomass of sardine and hence the TAC increased, increased catches were taken mostly from the area west of Cape Agulhas (Figure 7). The amount of sardine caught east of Cape Agulhas only increased from 2001 onwards, although remaining small in comparison with landings made to the west of Cape Agulhas until 2005, when for the first time since the start of the fishery catches east of Cape Agulhas exceeded those made west of Cape Agulhas. The relative exploitation level (catch as a function of biomass from the November survey in the previous year) east and west of Cape Agulhas shows a striking difference between the two areas (Figure 8). While the overall exploitation level for the total population averaged at around 10 % of the biomass during the period from 1987 to 2005, the exploitation level in the area west of Cape Agulhas increased substantially, particularly after 1999 and reaching 32 % in 2002. The exploitation level has remained high in the area west of Cape Agulhas and only recently has there been a slight increase in the level of exploitation east of Cape Agulhas.

Investigation of the length frequency structure of the western and eastern part of the population from November survey data shows that the sardine west of Cape Agulhas (Figure 9a) are represented mainly by 2 age classes, namely those fish that recruited to the population during the year (modal length 12 cm) and those that recruited during the previous year (modal length 16 cm). Very few older fish (>18 cm) are present in this area during the period between 1998 and 2005. Also evident is that the increase in biomass on the western part was mainly due to very strong recruitment from 2001 to 2003, resulting in a large number of two-year old fish in this area between 2002 and 2004. Subsequent low recruitment since 2004 has halted the increase in biomass west of Cape Agulhas and the number of fish remaining in this area has decreased substantially. Comparisons with the length frequency of the catches (apart from the recruits taken as part of the by-catch with the anchovy fishery that are <11 cm) landed throughout the year in the area west of Cape Agulhas (Figure 9b), indicates that most fish landed during this period were larger fish (>16 cm). This implies a greater level of exploitation on larger fish, particularly those >18 cm. The length frequency structure of fish found east of Cape Agulhas during November surveys (Figure 10a) is generally broader than that found west of Cape Agulhas and consists of a high number of larger fish (>18 cm). Also evident from this length structure is the increase in the number of particularly older fish as the biomass east of Cape Agulhas increased. A relatively large number of 1 and 1+-year old fish (10-14 cm and 14-16 cm respectively) are also found in this area. A comparison with the length frequency of the catches landed east of Cape Agulhas (Figure 10b), confirms the dominance of older fish in this region, and clearly shows the increase in catches over time in this region. Further investigation of the origin of the relatively large number of 1 and 1+-year old fish east of Cape Agulhas was warranted, given that recruitment of sardine measured in May each year was largely associated with the west coast and WAB (Figure 11). For most years, including years prior to those shown, recruitment east of Cape Agulhas was small in comparison to that west of Cape Agulhas, and also does not seem to be related to the relative abundance of sardine found west and east of Agulhas during the November survey of the previous year. Three years stand out, however, in which the relative importance of recruitment east of Cape Agulhas was high (1999, 2000 and 2003); these are also years in which the number of 1 and 1+ -year old fish found in November in the area east of Cape Agulhas was also high. Discussion The Operational Management Procedure (OMP) used in the assessment and management of the sardine population off the coast of South Africa currently assumes a single population of sardine and does not consider spatial aspects of the distribution or fishing effort. Recently, however, the observed eastward shift in the sardine stock as evidenced from acoustic surveys and changes in fishing patterns (Fairweather et al.

2006a) have led to the development of several hypothesis which might explain the underlying cause of the distributional change (van der Lingen et al. 2005). At the same time, the pelagic fishing industry is facing huge logistical and cost burdens as a result of having to transport a substantial portion of the landed sardine catch by road from a harbour on the south coast (Mossel Bay) to the processing factories situated on the west coast, and the change in sardine distribution has also resulted in the fishery being unable to fill the TAC in recent years (Figure 7). This is not an ideal situation, and while no compelling explanation has as yet been put forward for the cause of the eastward shift apart from a reduction in productivity on the west coast in 2001, work is already underway to revise the OMP in order to take into account the possible existence of two separate sardine stocks (i.e., a west stock and an east stock ). In the light of the OMP revision, the data put forward in this paper were analysed with the intention of highlighting spatial differences in the distribution of sardine in relation to fishing effort, and to provide insights into the possible causes of the perceived shift in distribution of sardine. Evidence of an increase in the area occupied by sardine as a function of increasing biomass is in accordance with the well know expansion and contaction of range occupied by small pelagic fish populations as their abundance increases or decreases (MacCall 1990). While Barange et al. (1999) did not observe this trend in an earlier analysis, their speculation that the range of abundance and spatial coverage at that time was not extensive enough to enable the observations of trends in degree of spatial coverage to be made seems feasible. Since their work, a fourfold increase in the biomass of sardine has been witnessed while at the same time the area occupied by sardine has been shown to vary threefold. Importantly, the major change in the degree of spatial coverage has been due to the increase in the size of the eastern part of the stock, which at times of low biomass was very small. The large increase in biomass of the sardine stock found east of Agulhas is possibly due to several factors; i.e, low relative exploitation rate, increased productivity relative to the western part of the population due to increased reproductive output (increased fecundity of larger fish, temperature effects on hatching, etc) and successful local recruitment on the east coast. The presence of a growing number of large sardine east of Cape Agulhas, particularly since 1999, may be indicative of a larger contribution to east coast recruitment due to retention in that area, particularly during winter, rather than the reliance on transport of eggs and larvae to the west coast during the summer spawning season. This in turn has led to a larger number of recruits either being retained east of Cape Agulhas in certain years, or to the return of fish to the area in which they were spawned east of Cape Agulhas. This may be the most important contributor to the dramatic increase in sardine biomass in the area east of Cape Agulhas. Diminished relative biomass in the area west of Cape Agulhas is probably due to higher than average exploitation levels on sardine west of Cape Agulhas. Based on these analyses it is possible to say that the perceived eastward shift in the sardine population is a result of an increase in the size of the eastern part of the population and the associated expansion in area occupied by this portion of the stock.

Furthermore, higher than average exploitation on the western part of the stock has exacerbated the situation. Spatially-explicit management strategies whereby the population is either managed as two separate stocks with independent recruitment mechanisms or whereby fishing effort and size selectivity of catches is managed in relation to available biomass must be and is being considered as a matter of urgency. It is, however, not known if a reduction in fishing effort west of Cape Agulhas will lead to an increase in biomass in this region, as much of the life history strategy of sardine is still poorly understood. Acknowledgments Members of the offshore surveys group of Marine and Coastal Management are acknowledged for their help in the collection and analysis of the acoustic survey data. Field station staff and Jan van der Westhuizen are thanked for collection and extraction of the commercial landings data. References Armstrong, M. J., Shelton, P. A. and R. M. Prosch 1985 Catch-based assessments of population size variability of pelagic fish species exploited in ICSEAF Division 1.6. Colln scient. Pap. int. Commn SE. Atl. Fish. 12(1): 17 29. Armstrong, M. J., Berruti, A. and J. Colclough 1987 Pilchard distribution in South African waters, 1983 1985.In The Benguela and Comparable Ecosystems. Payne,A. I. L., Gulland, J. A. and K. H. Brink (Eds). S. Afr. J. mar.sci. 5: 871 886. Armstrong, M. J., Chapman, P., Dudley, S. F. J., Hampton, I. and P. E. Malan 1991 Occurrence and population structure of pilchard Sardinops ocellatus, round herring Etrumeus whiteheadi and anchovy Engraulis capensis off the east coast of southern Africa. S. Afr. J. mar. Sci. 11: 227 249. Barange, M., Hampton, I. and B. A. Roel 1999 Trends in the abundance and distribution of anchovy and sardine on the South African continental shelf in the 1990s, deduced from acoustic surveys. In Benguela Dynamics: Impacts of Variability on Shelf- Sea Environments and their Living Resources. Pillar, S. C., Moloney, C. L., Payne, A. I. L. and F. A. Shillington. S. Afr. J. mar. Sci. 19: 367 391. Beckley, L.E. and C.D. van der Lingen 1999 Biology, fishery and management of sardines (Sardinops sagax) in southern African waters. Mar. Freshw. Res. 50, 955 978. Cochrane, K. L., Butterworth, D. S., De Oliveira, J. A. A. and B. A. Roel 1998 Management procedures in a fishery based on highly variable stocks with conflicting objectives: experiences in the South African pelagic fishery. Revs Fish Biol. Fish. 8: 177 214.

Crawford, R. J. M. 1980 Seasonal patterns in South Africa s Western Cape purseseine fishery. J. Fish Biol. 16(6): 649 664. Crawford, R. J. M., Shelton, P. A. and L. Hutchings 1980 Implications of availability, distribution and movements of pilchard (Sardinops ocellata) and anchovy (Engraulis capensis) for assessment and management of the South African purse-seine fishery. Rapp. P-v. Réun. Cons. perm. int. Explor. Mer 177: 355 373. Fairweather, T.P., van der Lingen, C.D., Booth, A.J., Drapeau, L., and J.J. van der Westhuizen 2006a Indicators of sustainable fishing for South African sardine (Sardinops sagax) and anchovy (Engraulis encrasicolus). Afr. J. mar. Sci 28(3/4): Fairweather, T.P., Hara, M., van der Lingen, C.D., Raakjaer Nielsen, J., Shannon, L.J., Louw, G.G., Degnbol, P. and R.J.M. Crawford 2006b The knowledge base for management of the capital-intensive fishery for small pelagic fish off South Africa. Afr. J. mar. Sci 28(3/4): Fowler, J. L. and A. J. Boyd 1998 Transport of anchovy and sardine eggs and larvae from the western Agulhas Bank to the West Coast during the 1993/94 and 1994/95 spawning seasons. In Benguela Dynamics: Impacts of Variability on Shelf-Sea Environments and their Living Resources. Pillar, S. C., Moloney, C. L., Payne, A. I. L. and F. A. Shillington (Eds). S. Afr. J. mar. Sci. 19: 181 195. Hampton, I. 1987 Acoustic study on the abundance and distribution of anchovy spawners and recruits in South African waters. In The Benguela and Comparable Ecosystems. Payne, A. I. L., Gulland, J. A. and K. H. Brink (Eds). S. Afr. J. mar. Sci. 5: 901 917. Hampton, I. 1992 The role of acoustic surveys in the assessment of pelagic fish resources on the South African continental shelf. In Benguela Trophic Functioning. Payne, A. I. L., Brink, K. H., Mann, K. H. and R. Hilborn (Eds). S. Afr. J. mar. Sci. 12: 1031 1050. Hutchings, L. 1992 Fish harvesting in a variable, productive environment searching for rules or searching for exceptions? In: Payne, A.I.L., Brink, K.H., Mann, K.H., Hilborn, R. (Eds.), Benguela Trophic Functioning. S. Afr. J. Mar. Sci. 12: 297 318. Hutchings, L., Barange, M., Bloomer, S.F., Boyd, A.J., Crawford, R.J. M., Huggett, J.A., Kerstan, M., Korrûbel, J.I., De Oliveira, J.A.A., Painting, S.J., Richardson, A.J., Shannon, L.J., Schuelein, F.H., van der Lingen, C.D. and H.M. Verheye 1998 Multiple factors affecting South African anchovy recruitment in the spawning, transport and nursery areas. In: Pillar, S.C., Moloney, C.L., Payne, A.I.L., Shillington, F.A. (Eds.), Benguela Dynamics. Impacts of Variability on Shelf-Sea Environments and their Living Resources. S. Afr. J. mar. Sci., 19 : 211 225.

Hutchings, L., Beckley, L.E., Griffiths, M.H., Roberts, M.J., Sundby, S. and C.D. van der Lingen 2002 Spawning on the edge: spawning grounds and nursery areas around the southern African coastline. Mar. Freshw. Res. 53: 307 318. Jolly, G. M. and I. Hampton 1990 A stratified random transect design for acoustic surveys of fish stocks. Can. J.Fish. aquat. Sci. 47(7): 1282 1291. Lett, C., Roy, C., Levassuer, A., van der Lingen, C.D. and C. Mullon 2006 Simulation and quantification of concentration and retention processes in the southern Benguela upwelling ecosystem. Fish. Oceanog. 15(5): 363-372. MacCall, A. D. 1990 Dynamic Geography of Marine Fish Populations. Seattle; University of Washington Press: 153 pp Miller, D.C.M., Moloney, C.L., van der Lingen, C.D., Lett, C., Mullon, C. and J.G. Field 2006 Modelling the effects of physical-biological interactions and spatial variability in spawning and nursery areas on transport and retention of sardine Sardinops sagax eggs and larvae in the southern Benguela ecosystem. J. Mar. Sys. 61(3-4): 212-229. Nelson, G. and L. Hutchings 1987 Passive transportation of pelagic system components in the southern Benguela area. In: Payne, A.I. L., Guiland, J.A., Brink, K.H. (Eds.), The Benguela and Comparable Ecosystems. S. Afr. J. Mar. Sci. 5: 223 234. Shelton, P.A. and L. Hutchings 1982 Transport of anchovy, Engraulis capensis Gilchrist, eggs and early larvae by a frontal jet current. J. Cons. Int. Explor. Mer 40: 185 198. Shelton, P. A. 1986 Fish spawning strategies in the variable southern Benguela Current region. Ph.D. thesis, University of Cape Town: [vi] + 327 pp. Twatwa, N.M., van der Lingen, C.D., Drapeau, L., Moloney, C.L. and J.G. Field 2005 Characterising and comparing the spawning habitats of anchovy Engraulis encrasicolus and sardine Sardinops sagax in the southern Benguela upwelling ecosystem. Afr. J. Mar. Sci. 27(2): 487-499. van Der Lingen, C. D. and J. A. Huggett 2003 The role of ichthyoplankton surveys in recruitment research and management of South African anchovy and sardine. In The Big Fish Bang. Proceedings of the 26th Annual Larval Fish Conference. Browman H. I. and A.B. Skiftesvik (Eds). Bergen, Norway; Institute of Marine Research: 303 343. van der Lingen, C.D., Hutchings, L., Merkle, D., van der Westhuizen, J.J., and J. Nelson 2001 Comparative spawning habitats of anchovy (Engraulis capensis) and sardine (Sardinops sagax) in the southern Benguela upwelling ecosystem. In: Kruse, G.H., Bez, N., Booth, T., Dorn, M., Hills, S., Lipcius, R.N., Pelletier, D., Roy, C., Smith, S.J., Witherell, D. (Eds.), Spatial Processes and Management of Marine Populations. University of Alaska Sea Grant, AK-SG-01-1158 02, Fairbanks, USA, pp. 185 209.

van der Lingen, C.D., Coetzee, J.C., Demarcq, H., Drapeau, L., Fairweather, T.P. and L. Hutchings 2005 An eastward shift in the distribution of southern Benguela sardine. GLOBEC Int. Newsl. 11: 17-22.

Figure 1. Map of South Africa showing the location of places mentioned in the text, the continental shelf (the 100m and 200m isobaths are shown) and the Agulhas and Benguela currents. The west coast system in this paper is defined as extending from Cape Agulhas westward and northwards, the Agulhas bank system is defined as the area east of Cape Agulhas (from Fairweather et al. 2006b).

4500 4000 November - Total biomass May - recruitment 80 70 Total sardine biomass (000 tons) 2 3500 3000 2500 2000 1500 1000 500 60 50 40 30 20 10 0 0 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 Recruitment (billions) 2 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 Figure 2. Annual estimates of total sardine biomass measured in November and sardine recruitment measured in May since 1984.

30 200m Hondeklipbaai 31 32 33 Doringbaai Lambert's Bay Cape Columbine Low Biomass Port Alfred East London Port St Johns 34 35 Cape Town Cape Agulhas Mossel Bay Port Elizabeth 36 37 Sardine density (g.m -2 ) 1 to 10 10 to 25 25 to 50 50 to 100 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 30 31 32 33 200m Hondeklipbaai Doringbaai Lambert's Bay Cape Columbine Medium Biomass East London Port Alfred Port St Johns 34 35 Cape Town Cape Agulhas Mossel Bay Port Elizabeth 36 37 Sardine density (g.m -2 ) 1 to 10 10 to 25 25 to 50 50 to 100 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 30 31 32 33 200m Hondeklipbaai Doringbaai Lambert's Bay Cape Columbine High Biomass Port Alfred East London Port St Johns 34 35 Cape Town Cape Agulhas Mossel Bay Port Elizabeth 36 37 Sardine density (g.m -2 ) 1 to 10 10 to 25 25 to 50 50 to 100 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Figure 3. Composite density maps derived from November survey data for periods of low, medium, and high sardine biomass.

Area occupied (square nm) 25000 20000 15000 10000 5000 90 89 91 87 92 86 88 y = 396.8x 0.482 R 2 = 0.8654 96 95 93 94 05 97 99 98 00 01 04 03 02 0 0 1000 2000 3000 4000 5000 Spawner Biomass (000 tons) Figure 4. The total area occupied by sardine as a function of biomass from November survey data. 20000 Area occupied (square nm) 15000 10000 5000 0 West of Agulhas East of Agulhas 0 500 1000 1500 2000 2500 3000 3500 Spawner Biomass (000 tons) Figure 5. Comparison of the area occupied by sardine in relation to biomass east and west of Cape Agulhas.

West of Agulhas East of Agulhas 4500 4000 3500 3000 2500 2000 1500 1000 500 0 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 Biomass (000 tons) Figure 6. Acoustic biomass measured east and west of Cape Agulhas during November surveys. TAC and Catch (000 tons) 500 450 400 350 300 250 200 150 100 50 0 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 West of Agulhas East of Agulhas TAC 2003 2004 2005 Figure 7. Annual Total Allowable Catch (TAC) and actual landed catches taken by commercial fisherman east and west of Cape Agulhas.

35 30 West of Agulhas East of Agulhas Exploitation level (%) 25 20 15 10 Average exploitation level for whole population 5 0 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 Figure 8. Exploitation level (annual catch/biomass in November of the previous year) east and west of Cape Agulhas.

(a) Length frequency in November west of Cape Agulhas (b) Length frequency of the catch taken west of Cape Agulhas Figure 9. Length frequency of sardine measured west of Cape Agulhas from November survey data (a) and from commercial catches (b).

(a) Length frequency in November east of Cape Agulhas (b) Length frequency of the catch taken east of Cape Agulhas Figure 10. Length frequency of sardine measured east of Cape Agulhas from November survey data (a) and from commercial catches (b).

70 60 West of Agulhas East of Agulhas Recruitment (Billion Fish) 50 40 30 20 10 0 1998 1999 2000 2001 2002 2003 2004 2005 2006 Figure 11. Recruitment measured during May since 1998 for the area west and east of Cape Agulhas.