On the relation between schools, clusters of schools, and abundance in pelagic fish stocks

Petitgas, Pierre; Reid, David G.; Carrera, Pablo; Iglesias, M.; Georgakarakos, S.; Liorzou, B.; Massé, Jacques

doi:10.1006/jmsc.2001.1130

Cited by 63 publications

(53 citation statements)

References 20 publications

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“…The 'echo integration by shoal' process was employed (Scalabrin & Massé 1993, Petitgas et al 2001, Guillard et al 2004), which did not take into consideration the individual fish but rather the structure of fish schools, employing the echo types defined above. Graphical measure corrections on fish schools were carried out according to Johannesson & Losse (1977).…”

Section: Methodsmentioning

confidence: 99%

Schooling behaviour of small pelagic fish: phenotypic expression of independent stimuli

Brehmer¹,

Gerlotto²,

Laurent³

et al. 2007

Mar. Ecol. Prog. Ser.

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We compared echo sounder measurements of fish schools on Venezuelan and Senegalese coastal shelves. In both areas Sardinella aurita was the predominant aggregative species; the stocks are known to be genetically independent. Persistent school typology is described by analysing 7 acoustic surveys in Venezuela and comparing with pioneer observations in Senegal. The echo types encountered in both countries were comparable, with S. aurita and their associated species having comparable schooling behaviour. School morphology appears to be more related to species than to global characteristics of their ecosystems, as fish school descriptors were similar for both stocks. Nevertheless, S. aurita may adopt different school morphologies. Differentiation between day and night fish schools was mainly due to morphological variables, as determined by fractal dimension. Echo types were different between day and night in both Venezuela and Senegal. This analysis shows that several independent parameters can influence school morphology. However, although schooling behaviour is temporally highly variable, it shows several constant, typical 2D morphological structures, i.e. echo types. The observation of small pelagic fish schools occurring during the night is not unusual according to the literature, although a strict diurnal schooling behaviour, with scattering during the night, is often reported. Schooling behaviour appears to be a phenotypic expression depending on biotic and abiotic stimuli, intrinsic characteristics and motivation.

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Section: Methodsmentioning

confidence: 99%

Schooling behaviour of small pelagic fish: phenotypic expression of independent stimuli

Brehmer¹,

Gerlotto²,

Laurent³

et al. 2007

Mar. Ecol. Prog. Ser.

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“…To test different environmental conditions in consecutive years, the years 2001 to 2003 were chosen after the analysis of satellite data spanning two decades, the 1990's and 2000's. The data sets revealed that 2001 was an exceptionally warm year, particularly in summer, with strong stratification mainly because of reduced wind stress in the winter of -2001(McQuatters-Gollop et al, 2008Buongiorno Nardelli et al, 2010). The year 2002 was average in terms of temperature distribution and 2003 was remarkably cold when compared to the mean conditions, with significantly higher wind stress (McQuatters-Gollop et al, 2008).…”

Section: Design Of Simulationsmentioning

confidence: 99%

“…Georgia's fishing fleet is much smaller (CastillaEspino et al, 2014) and Georgian fishery enterprises hire a limited number of Turkish purse seiners each year. The fact that anchovy aggregate to form dense schools when overwintering makes them specifically vulnerable to exploitation and potential overexploitation (Auckland and Reid, 1998;Petitgas et al, 2001). …”

Section: An Overview Of the Black Sea Anchovy Fishery Characteristicsmentioning

confidence: 99%

Understanding the Impact of Environmental Variability on Anchovy Overwintering Migration in the Black Sea and its Implications for the Fishing Industry

2017

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Black Sea anchovy (Engraulis encrasicolus) undertake extensive overwintering migrations every fall from nursery grounds to warmer overwintering areas located on the south-eastern coast of the Black Sea. During migration and particularly upon arrival at the Anatolian coast, they support an important fishery and valuable source of income for the regional community. Black Sea anchovy have undergone significant stock fluctuations partly related to climatic conditions; for example, migrating anchovy schools arrived late or failed to arrive at the Anatolian coast when fall temperatures increased. It is therefore of importance to understand the conditions required for successful overwintering migration and explore different migration routes. This study invokes a Lagrangian modeling approach applied to satellite derived circulation and temperature data as a first attempt to model anchovy migration dynamics in the Black Sea. This modeling approach takes the influence of the physical environment into account, while the quality of overwintering grounds, adaptive, schooling, and homing behavior is neglected. The model is used to investigate the possible influence of interannual and seasonal variability of temperature and surface currents, as well as the influence of migration behavior on the success of anchovy overwintering migration for both the Black Sea and Azov Sea anchovy. The results of the present work show the possibility that overwintering anchovy fished along the Turkish Eastern Anatolian coast may not exclusively originate from the northwestern shelf, but mainly from the eastern Black Sea basin. Migration pathways are identified for both Black Sea and Azov Sea anchovy, which are of importance for the national fisheries efforts of riparian countries. The modeling results are in agreement with general patterns of anchovy migration given in the literature indicating that the physical environment may be a major factor in shaping general migration patterns. Simulation results are used to hypothesize about alternatives to previously determined migration routes and provide potential reasons that explain the inability of the Bulgarian anchovy fishery to recover. Results show that the intensity and timing of autumnal cooling, coupled with current Guraslan et al.Environmental Impact on Anchovy Overwintering Migration strength, can be of significant importance in determining annual and seasonal variability of migration success. Considering the need for fisheries management to account for the variability in fishable overwintering anchovy stocks a modeling approach as developed in the current study may provide such a tool.

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“…These species form either pure or mixed schools (Bakun & Cury 1999) and may adjust their spatial extension to maintain constant density within schools (Petitgas et al 2001). The organization of schools into clusters has already been described for many stocks (Freon & Misund 1999, Petitgas et al 2001 and references therein), and is probably related to the patchiness of the environment (Schneider 1989, Swartzman 1991. Within a cluster of schools the spatial distribution can be very heterogeneous.…”

Section: Introductionmentioning

confidence: 94%

Effect of coastal topography on the spatial structure of the populations of small pelagic fish

Giannoulaki¹,

Machias²,

Koutsikopoulos³

et al. 2003

Mar. Ecol. Prog. Ser.

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Acoustic data from 6 research surveys (4 in summer and 2 in winter) in the Aegean and Ionian Seas (eastern Mediterranean Sea) were analyzed to examine the effect of coastal topography on the spatial structure of populations of small pelagic fish using geostatistical techniques (omnidirectional and exhaustive variograms). The effect of topographic characteristics related to depth and the degree of land enclosure on the spatial structure of fish populations (as expressed by several parameters calculated from omnidirectional and exhaustive variograms) was studied by multiple regression analysis. The estimated autocorrelation range of omnidirectional variograms indicated that fish formed meso-scale to large-scale patches, but it was not significantly related to any of the area characteristics examined. The nugget effect was negatively correlated with mean bottom depth. Parameters related to anisotropy, calculated from the exhaustive variograms, did not show any consistent pattern related to the geographical characteristics of the area studied. Geometric descriptors of the exhaustive variograms provided a more detailed picture of the underlying spatial continuity, indicating the effect of the enclosure index (stronger in summer) and the size of the area (stronger in winter) on the spatial structure of fish populations. The organization of fish into clusters of schools was heterogeneous in closed sub-areas during both seasons and, for a given degree of enclosure, they were more homogeneous in small-sized sub-areas than in large sub-areas. These results suggest that the environmental spatial heterogeneity mainly affected the way schools were organized into aggregations rather than the maximum size of the area occupied by these aggregations.KEY WORDS: Small pelagic fish · Spatial structure · Degree of enclosure · Exhaustive variograms Resale or republication not permitted without written consent of the publisher

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On the relation between schools, clusters of schools, and abundance in pelagic fish stocks

Cited by 63 publications

References 20 publications

Schooling behaviour of small pelagic fish: phenotypic expression of independent stimuli

Schooling behaviour of small pelagic fish: phenotypic expression of independent stimuli

Understanding the Impact of Environmental Variability on Anchovy Overwintering Migration in the Black Sea and its Implications for the Fishing Industry

Effect of coastal topography on the spatial structure of the populations of small pelagic fish

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