Ecological Archives M085-005-A1

John R. Morrongiello and Ronald E. Thresher. 2015. A statistical framework to explore ontogenetic growth variation among individuals and populations: a marine fish example. Ecological Monographs 85:93115. http://dx.doi.org/10.1890/13-2355.1

Appendix A. Supplementary results: Age-class specific fish length ~ otolith radius relationships.

The use of otolith increment data to reconstruct growth histories assumes otolith growth is proportional to somatic growth (Campana 1990, Francis 1990). The best way to test this assumption is to compare otolith increment measurements with length or weight data derived from mark–recapture studies (Campana 2001), but unfortunately this kind of data is often not available, or of appropriate temporal resolution, for this purpose. Therefore, the assumption is commonly tested and quantified by correlating otolith size to fish size (e.g., Baumann et al. 2013), although this typically further assumes a constant linear relationship between the two parameters (Campana 1990, Günther et al. 2012). We tested the assumption that otolith increments are a proxy for somatic growth for tiger flathead in two ways. First, overall, bigger fish (in length) had wider otoliths (β = 21.912 (± 0.194) fish cm.otolith mm-1; linear regression, n = 6113, R² = 0.677, p < 0.001). This relationship is consistent with the hypothesis, but could also result from an age effect rather than growth per se, whereby bigger (older) fish have more annual increments and thus wider otoliths. Hence, second, we tested for age class-specific relationships between otolith radius and fish size. In each of the sixteen age classes with adequate sample sizes (n ≥ 10; age classes 2–17 years), larger fish had wider otolith radii (all significant (p < 0.05) bar age 17, with an average R² of 0.217 (range 0.086–0.422); Table A1). The relatively low amount of variance accounted for within each age class is likely to reflect sample sizes, measurement errors, nonlinearities in the relationship and the limitation of using only body length (as opposed to girth, depth or weight) as an index of somatic growth (e.g., Günther et al. 2012).

Table A1. Results of linear regressions for age class-specific relationships between fish length (cm) and otolith radius (mm) for tiger flathead, pooled across zones.

age class

sample size

intercept

slope (radius)

R²

P value

overall (2–28)

6113

11.047

21.914

0.677

<0.001

2

816

12.706

17.297

0.184

<0.001

3

1110

20.727

11.938

0.142

<0.001

4

1205

19.508

14.717

0.231

<0.001

5

758

22.227

12.903

0.185

<0.001

6

769

26.249

10.463

0.129

<0.001

7

575

26.852

10.605

0.110

<0.001

8

279

29.017

9.936

0.086

<0.001

9

171

23.836

14.833

0.172

<0.001

10

116

29.764

11.6000

0.087

0.001

11

116

31.466

10.307

0.088

0.001

12

58

31.594

10.059

0.075

0.037

13

47

6.309

25.597

0.390

<0.001

14

33

13.787

21.437

0.258

0.003

15

17

13.243

21.228

0.422

0.005

16

18

17.934

19.336

0.359

0.009

17

10

37.295

8.040

0.097

0.382

 

Literature cited

Baumann, H., S. J. Sutherland, and R. S. McBride. 2013. Longitudinal length back-calculations from otoliths and scales differ systematically in haddock. Transactions of the American Fisheries Society 142:184–192.

Campana, S. E. 1990. How reliable are growth back-calculations based on otoliths? Canadian Journal of Fisheries and Aquatic Sciences 47:2219–2227.

Campana, S. E. 2001. Accuracy, precision and quality control in age determination, including a review of the use and abuse of age validation methods. Journal of Fish Biology 59:197–-242.

Francis, R. I. C. C. 1990. Back-calculation of fish length: a critical review. Journal of Fish Biology 36:883–904.

Günther, C. C., A. Temming, H. Baumann, B. Huwer, C. Moellmann, C. Clemmesen, and J.-P. Herrmann. 2012. A novel length back-calculation approach accounting for ontogenetic changes in the fish length - otolith size relationship during the early life of sprat (Sprattus sprattus). Canadian Journal of Fisheries and Aquatic Sciences 69:1214–1229.


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