Environmental Biology of Fishes

, Volume 95, Issue 1, pp 127–146

Comparative feeding ecology of shortfin mako, blue and thresher sharks in the California Current

  • Antonella Preti
  • Candan U. Soykan
  • Heidi Dewar
  • R. J. David Wells
  • Natalie Spear
  • Suzanne Kohin
Article

DOI: 10.1007/s10641-012-9980-x

Cite this article as:
Preti, A., Soykan, C.U., Dewar, H. et al. Environ Biol Fish (2012) 95: 127. doi:10.1007/s10641-012-9980-x

Abstract

This study describes the feeding ecology of three pelagic shark species in the California Current: shortfin mako (Isurus oxyrinchus); blue (Prionace glauca); and thresher (Alopias vulpinus) sharks. Stomach contents of sharks collected from 2002 to 2008 were identified to the lowest taxonomic level and analyzed using univariate and multivariate methods. Of 330 mako sharks sampled (53 to 248 cm fork length [FL]), 238 stomachs contained 42 prey taxa, with jumbo squid (Dosidicus gigas) and Pacific saury (Cololabis saira) representing the most important prey based on the geometric index of importance (GII). In addition, 158 blue sharks were sampled (76 to 248 cm FL) and 114 stomachs contained 38 prey taxa, with jumbo and Gonatus spp. squids representing the most important prey. Lastly, 225 thresher sharks were sampled (108 to 228 cm FL) and 157 stomachs contained 18 prey taxa with northern anchovy (Engraulis mordax) and Pacific sardine (Sardinops sagax) identified as the most important prey. Overall, mako sharks had the most diverse diet based upon Simpson’s diversity index (1/D) (8.43 ± 1.16), feeding on many species of teleosts and cephalopods, followed by blue sharks (6.20 ± 2.11) which consumed a wide range of prey (primarily cephalopods), while thresher sharks were most specialized (2.62 ± 0.34), feeding primarily on coastal pelagic teleosts. Dietary overlap was lowest between blue and thresher sharks (Sørensen similarity index = 0.321 and Simplified Morisita Horn index = 0.006), and seasonal variability in diet was greatest for blue sharks (Simplified Morisita Horn index = 0.260, Analysis of Similarity (ANOSIM) p < 0.001). In addition, size class, and subregion were significant factors that affected diet of each species differently (ANOSIM p < 0.001). Despite similarities in life history characteristics and spatial and temporal overlap in habitat, diets of these three common shark species are distinct in the California Current.

Keywords

Shortfin makoBlue sharkThresher sharkCalifornia CurrentDiet analysisFeeding ecology

Supplementary material

10641_2012_9980_MOESM1_ESM.doc (114 kb)
Table S1Rarefied Richness and Simpson Diversity (1/D) results. Mean = the mean value of the index based on 100 bootstrap estimates; SE = standard error of bootstrap estimates. Indices were not calculated for those comparisons in which one of the pair had <10 samples, these are indicated with “NA”. 95% confidence intervals were generated using the following formula: mean ± 1.96*SE. Sample sizes for all rarefied richness comparisons are based on the category with the smallest sample size; sample sizes for Simpson diversity calculations incorporated all available samples. (DOC 114 kb)
10641_2012_9980_MOESM2_ESM.doc (104 kb)
Table S2Similarity results based on comparisons among species, fishing seasons, size classes, subregions and sexes. SMH = Simplified Morisita-Horn index. Indices were not calculated for those comparisons in which one of the pair had <10 samples, these are indicated with “NA”. (DOC 103 kb)
10641_2012_9980_MOESM3_ESM.doc (35 kb)
Table S3Quantitative prey composition of shortfin makos, less than 110 cm FL, in the California Current. A total of 64 stomachs containing food were examined. Prey items are shown by decreasing values of GII. See methods for descriptions of the measured values. (DOC 35.0 kb)
10641_2012_9980_MOESM4_ESM.doc (42 kb)
Table S4Quantitative prey composition of shortfin makos, 110–149 cm FL, in the California Current. A total of 125 stomachs containing food were examined. Prey items are shown by decreasing values of GII. See methods for descriptions of the measured values. (DOC 41.5 kb)
10641_2012_9980_MOESM5_ESM.doc (40 kb)
Table S5Quantitative prey composition of shortfin makos, 150 and greater cm FL, in the California Current. A total of 47 stomachs containing food were examined. Prey items are shown by decreasing values of GII. See methods for descriptions of the measured values. (DOC 40.5 kb)
10641_2012_9980_MOESM6_ESM.doc (34 kb)
Table S6Quantitative prey composition of blue sharks, less than 110 cm FL, in the California Current. A total of 34 stomachs containing food were examined. Prey items are shown by decreasing values of GII. See methods for descriptions of the measured values. (DOC 34.5 kb)
10641_2012_9980_MOESM7_ESM.doc (39 kb)
Table S7Quantitative prey composition of blue sharks, 110–149 cm FL, in the California Current. A total of 49 stomachs containing food were examined. Prey items are shown by decreasing values of GII. See methods for descriptions of the measured values. (DOC 39.0 kb)
10641_2012_9980_MOESM8_ESM.doc (36 kb)
Table S8Quantitative prey composition of blue sharks, 150 and greater cm FL, in the California Current. A total of 29 stomachs containing food were examined. Prey items are shown by decreasing values of GII. See methods for descriptions of the measured values. (DOC 36.5 kb)
10641_2012_9980_MOESM9_ESM.doc (58 kb)
Table S9Quantitative prey composition of thresher sharks, less than 167 cm FL, in the California Current. A total of 95 stomachs containing food were examined. Prey items are shown by decreasing values of GII. See methods for descriptions of the measured values. (DOC 58 kb)
10641_2012_9980_MOESM10_ESM.doc (56 kb)
Table S10Quantitative prey composition of thresher sharks, 167 and greater cm FL, in the California Current. A total of 62 stomachs containing food were examined. Prey items are shown by decreasing values of GII. See methods for descriptions of the measured values. (DOC 55 kb)
10641_2012_9980_MOESM11_ESM.doc (45 kb)
Table S11Quantitative prey composition of shortfin makos within the SBC subregion. A total of 184 stomachs containing food were examined. Prey items are shown by decreasing values of GII. See methods for descriptions of the measured values. (DOC 45.0 kb)
10641_2012_9980_MOESM12_ESM.doc (37 kb)
Table S12Quantitative prey composition of shortfin makos beyond the SBC subregion. A total of 54 stomachs containing food were examined. Prey items are shown by decreasing values of GII. See methods for descriptions of the measured values. (DOC 37.0 kb)
10641_2012_9980_MOESM13_ESM.doc (44 kb)
Table S13Quantitative prey composition of blue sharks within the SBC subregion. A total of 84 stomachs containing food were examined. Prey items are shown by decreasing values of GII. See methods for descriptions of the measured values. (DOC 35.0 kb)
10641_2012_9980_MOESM14_ESM.doc (38 kb)
Table S14Quantitative prey composition of blue shark beyond the SBC subregion. A total of 30 stomachs containing food were examined. Prey items are shown by decreasing values of GII. See methods for descriptions of the measured values. (DOC 37.5 kb)
10641_2012_9980_MOESM15_ESM.doc (58 kb)
Table S15Quantitative prey composition of thresher sharks within the SBC subregion. A total of 146 stomachs containing food were examined. Prey items are shown by decreasing values of GII. See methods for descriptions of the measured values. (DOC 58 kb)
10641_2012_9980_MOESM16_ESM.doc (45 kb)
Table S16Quantitative prey composition of thresher sharks beyond the SBC subregion. A total of 11 stomachs containing food were examined. Prey items are shown by decreasing values of GII. See methods for descriptions of the measured values. (DOC 45 kb)
10641_2012_9980_MOESM17_ESM.doc (111 kb)
Fig. S1(Supplement figure) Cumulative prey curve for mako, blue and thresher sharks (prey identified to the family-level). (DOC 111 kb)

Copyright information

© Springer Science+Business Media B.V. (outside the USA) 2012

Authors and Affiliations

  • Antonella Preti
    • 1
  • Candan U. Soykan
    • 1
  • Heidi Dewar
    • 1
  • R. J. David Wells
    • 1
  • Natalie Spear
    • 1
  • Suzanne Kohin
    • 1
  1. 1.Fisheries Resources Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric AdministrationLa JollaUSA