Forecasts of recruitment in South African anchovy from SARP field data using a simple deterministic expert system

Painting, SJ; Korrûbel, J. L.

doi:10.2989/025776198784126926

Cited by 9 publications

(11 citation statements)

References 7 publications

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“…Several studies have incorporated these (and other) factors into models that attempt to predict recruitment success of anchovy in the southern Benguela region (e.g. Cochrane and Hutchings 1995;Painting and Korrûbel 1998;Miller and Field 2002).…”

Section: Introductionmentioning

confidence: 99%

Impact of environmental factors on survival of larval and juvenile Cape anchovy Engraulis encrasicolus (G.) in the southern Benguela upwelling region, determined from hatchdate distributions: implications for recruitment

Wilhelm¹,

Painting

Field

et al. 2005

Mar. Freshwater Res.

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March larval and May juvenile Cape anchovy of the unusually strong 1999/2000 year-class were collected off South Africa. Age estimates were obtained from daily increment counts on otoliths using light microscopy for March larvae (14–70 mm standard length, SL, n = 193, 92% success rate), and scanning electron microscopy for May juveniles (52–110 mm SL, n = 80, 22% success rate). Differences between March and May hatchdate distributions were related to the prevailing temperatures. March larval hatchdate distributions showed slight modes in October/November 1999 and January/February 2000, each a month later than May juvenile hatchdate distributions (September/October and November/December). Thus, mortality rates of larvae hatched after mid-December seem to have been higher. Large areas of warm water (19–26°C sea surface temperature) on the Agulhas Bank, mid-November 1999 to March 2000, indicated conditions conducive to spawning and reduced offshore advection of spawning products. A period of strong upwelling, March to May 2000, is likely to have increased availability of planktonic food for older larvae; also causing offshore dispersal of younger larvae and food patches required by these, possibly leading to starvation mortality of younger larvae during strong upwelling. The critical period thus seemed to be later than at first-feeding.

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Section: Introductionmentioning

confidence: 99%

Impact of environmental factors on survival of larval and juvenile Cape anchovy Engraulis encrasicolus (G.) in the southern Benguela upwelling region, determined from hatchdate distributions: implications for recruitment

Wilhelm¹,

Painting

Field

et al. 2005

Mar. Freshwater Res.

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“…Previous attempts to forecast anchovy recruitment in the southern Benguela have mainly followed 2 different approaches: the establishment of empirical relationships between environmental or biological variables and recruitment strength , and the development of expert systems , Painting & Korrûbel 1998. Some of the environmental relationships were conflicting, and none withstood the 'test of time', although the expert system approach shows considerable promise.…”

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confidence: 99%

“…A number of theories addressing likely sources of egg and larval mortality, and hence recruitment success, have been developed over the previous century; these have been comprehensively reviewed by Anderson (1988) and Cole & McGlade (1998). It is now generally recognised that no single factor or event is responsible for determining year-class strength, and concepts that integrate a number of processes influencing recruitment are gaining prominence, such as the optimal environmental window (OEW) theory of Cury & Roy (1989) and Bakun's (1996) triad hypothesis, which suggests that enrichment, concentration, and retention are important processes influencing the recruitment success of coastal pelagic fishes.Previous attempts to forecast anchovy recruitment in the southern Benguela have mainly followed 2 different approaches: the establishment of empirical relationships between environmental or biological variables and recruitment strength , and the development of expert systems , Painting & Korrûbel 1998. Some of the environmental relationships were conflicting, and none withstood the 'test of time', although the expert system approach shows considerable promise.…”

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confidence: 99%

Modelling the transport success of anchovy Engraulis encrasicolus eggs and larvae in the southern Benguela: the effect of spatio-temporal spawning patterns

Huggett¹,

Fréon²,

Mullon³

et al. 2003

Mar. Ecol. Prog. Ser.

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Recruitment success of anchovy Engraulis encrasicolus in the southern Benguela is thought to depend largely on the passive transport of eggs and larvae from their warm-water spawning area, located in the southern part of their distribution range (Agulhas Bank), to their cold-water nursery grounds located 500 km away on the west coast of South Africa. In order to test this hypothesis, the output of a 3D hydrodynamic model was coupled to a particle-tracking model, allowing the quantification of different factors such as the timing and precise location of spawning activity, the frequency of spawning activity within a month, the level of aggregation of the spawning stock, and the interannual variability of transport due to mesoscale processes. Results from the model indicate that spawning season and area have a major effect on transport success. The most favourable period for spawning was September to March, peaking in November, and the western Agulhas Bank was the most favourable spawning area. A low success rate of passive transport to the core inshore nursery area in the model suggests that additional processes such as swimming or advection are required for larvae to reach this area. In general, there was good agreement between observed spawning patterns and the optimal temporal and spatial strata where particle transport was most successful, suggesting that the spawning strategy of anchovy is mainly the result of an adaptation to the circulation patterns in the region. Nonetheless, some discrepancies were observed between the success of transport and actual spawning patterns, and temperature may also be an important factor to take into consideration to fully explain how this originally temperate species is able to survive in an area of highly contrasting temperatures.KEY WORDS: Individual-based model · Transport success · Anchovy · Ichthyoplankton · Recruitment · Reproductive strategy · Southern Benguela · Engraulis encrasicolus Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 250: [247][248][249][250][251][252][253][254][255][256][257][258][259][260][261][262] 2003 total purse-seine fishery catch (Barange et al. 1999). Catches during the 1950s and early 1960s were dominated by adult sardine, peaking at ~400 000 t in 1961-62, but declined to <100 000 t by 1967 ). This collapse was followed by a rapid increase in catches of anchovy, which replaced sardine as the dominant species during the 1970s and 1980s (Crawford et al. 1987). In addition to these decadalscale fluctuations in abundance, direct acoustic estimates of pelagic fish abundance since 1984 (Hampton 1987, Barange et al. 1999) have indicated considerable annual variability in recruitment of both sardine and anchovy, particularly the latter (Fig. 1). Estimated variations in anchovy recruitment were 5-fold during the period 1984 to 1999 and increased to nearly 20-fold after 2 yr of exceptional recruitment in 2000 and 2001. Recruitment of pelagic fish is the net result of a continuous series of l...

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“…Each variable was assessed against its threshold value (Fig. 4) in order to derive a decision table (Table 2) on which the forecasts (hindcasts, Table 3) were based (see Painting and Korrûbel, 1998). Of the three possible categories of BAR (Table 3), those considered to be useful to management in setting the initial TAC's are only `likely' and `very likely'.…”

Section: Resultsmentioning

confidence: 99%

Environmental and biological monitoring for forecasting anchovy recruitment in the southern Benguela upwelling region

Painting¹,

Hutchings²,

Huggett³

et al. 1998

Fisheries Oceanography

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Environmental and biological sampling and monitoring have been carried out in the southern Benguela since 1988. The overall goal of this research is to investigate environmental factors affecting anchovy recruitment and to develop the ability to forecast anchovy recruitment from year‐to‐year using field data obtained during the spawning season (August to March). Sampling was conducted at three different temporal and spatial scales: during annual (November) broad‐scale hydro‐acoustic surveys to determine spawner biomass on the entire spawning ground and in the core transport and recruitment areas; during monthly surveys in the core spawning, transport and recruitment regions over two entire spawning seasons (1993/94 and 1994/95); and during weekly sampling (since 1995) along a single transect downstream from the spawning area. Annual surveys provide the best spatial coverage, but are inadequate for representing environmental conditions and anchovy spawning success over a prolonged season. Weekly sampling provides the best temporal coverage, but logistical constraints restrict information to a limited portion of the spawning area and a reduced number of variables. Monthly surveys provide intermediate coverage in time and space, but are expensive and labour‐intensive. Forecasting anchovy recruitment has been based on two different approaches: the establishment of empirical relationships, and the development of rule‐based expert systems. Forecasts from deterministic expert systems have compared well with final estimates of recruitment strength, and indicate that environmental and biological variables may be used in a structured way to forecast anchovy recruitment.

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Forecasts of recruitment in South African anchovy from SARP field data using a simple deterministic expert system

Cited by 9 publications

References 7 publications

Impact of environmental factors on survival of larval and juvenile Cape anchovy Engraulis encrasicolus (G.) in the southern Benguela upwelling region, determined from hatchdate distributions: implications for recruitment

Impact of environmental factors on survival of larval and juvenile Cape anchovy Engraulis encrasicolus (G.) in the southern Benguela upwelling region, determined from hatchdate distributions: implications for recruitment

Modelling the transport success of anchovy Engraulis encrasicolus eggs and larvae in the southern Benguela: the effect of spatio-temporal spawning patterns

Environmental and biological monitoring for forecasting anchovy recruitment in the southern Benguela upwelling region

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