Effects of stomach content and gonad mass on length–weight relationships and condition indices in fish species with different body shapes

Hasan Cerim; Özgen Yilmaz; Sercan Yapici; İsmail Reis; Ozan Soykan; Bahadır Önsoy; Anıl Gülşahin; Ferhat Yalgın

doi:10.26881/oahs-2026.1.16

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Effects of stomach content and gonad mass on length–weight relationships and condition indices in fish species with different body shapes

Oceanological and Hydrobiological Studies

Volume 55 (2026): Issue 2 (June 2026)

By: Hasan Cerim, Özgen Yilmaz, Sercan Yapici, İsmail Reis, Ozan Soykan, Bahadır Önsoy, Anıl Gülşahin and Ferhat Yalgın

Open Access

|Jun 2026

Figures & Tables

Distribution of TL (A) and total body weight (B) among the studied species. Boxes represent interquartile ranges, horizontal lines indicate medians, and whiskers show the range of observed values. TL, total length.

LWR of the studied species based on different weight types. Lines represent fitted power models for gutted weight (F), total body weight (TW), and gonad-adjusted weight (TWG). LWR, length–weight relationships.

Sensitivity of statistical significance to increasing simulated GSI values in D. annularis. Red points indicate the approximate GSI thresholds at which statistical significance (p < 0.05) was reached for the respective comparisons. GSI, gonadosomatic index.

LWR parameters for each species under different weight definitions_

Species	Weight type	N	TL_min – TL_max	TW_min – TW_max	a	b	SE (b)	95% CI (b)	R²	Growth type
B. boops	TW	37	10.2–16.1	9.12–30.41	0.0098	2.9181	0.134	2.6454–3.1908	0.931	I
	TWG			9.58–31.93	0.0103	2.9181	0.134	2.6454–3.1908	0.931	I
	F			8.48–29.45	0.0095	2.9038	0.132	2.6355–3.1720	0.932	I
C. linguatula	TW	62	5.5–19.9	1.17–63.16	0.0062	3.0578	0.046	2.9666–3.1491	0.986	I
	TWG			1.21–65.18	0.0064	3.0578	0.047	2.9619–3.1498	0.987	I
	F			1.14–59.84	0.0063	3.0279	0.043	2.9413–3.1145	0.987	I
D. annularis	TW	60	9.2–15.0	11.37–61.46	0.01	3.2113	0.085	3.0416–3.3810	0.961	A+
	TWG			13.12–70.92	0.0115	3.2113	0.085	3.0416–3.3810	0.961	A+
	F			10.7–56.74	0.0097	3.1928	0.078	3.0360–3.3496	0.966	A+

Sample size and morphometric characteristics of the studied fish species_

	N	TL_min - TL_max	TL_mean	S.D.	S.E.	TW_min – TW_max	TW_mean	S.D.	S.E.
D. annularis	60	9.2–15.0	11.65	1.24	0.16	11.37–61.46	27.68	10.03	1.29
B. boops	37	10.2–16.1	12.35	1.35	0.22	9.12–30.41	15.53	5.25	0.86
C. linguatula	62	5.5–19.9	12.71	2.71	0.34	1.17–63.16	16.91	12.32	1.56

Pairwise comparisons of Fulton’s condition factor (K) among different weight definitions for each species_

Species	Comparison	Mean K values	p-value	Difference
B. boops	F vs TW	0.749 vs 0.7989	p = 0.0017	Significant (p < 0.05)
	F vs TWG	0.749 vs 0.8389	p < 0.001	Significant (p < 0.05)
	TW vs TWG	0.7989 vs 0.8389	p = 0.0167	Significant (p < 0.05)
C. linguatula	F vs TW	0.6734 vs 0.7153	p < 0.001	Significant (p < 0.05)
	F vs TWG	0.6734 vs 0.7382	p < 0.001	Significant (p < 0.05)
	TW vs TWG	0.7153 vs 0.7382	p = 0.0278	Significant (p < 0.05)
D. annularis	F vs TW	1.559 vs 1.680	p < 0.001	Significant (p < 0.05)
	F vs TWG	1.559 vs 1.938	p < 0.001	Significant (p < 0.05)
	TW vs TWG	1.680 vs 1.938	p < 0.001	Significant (p < 0.05)

Paired comparisons of mean body weights (F, TW, and TWG) across species_

Species	Comparison	Mean weights (g)	p-value	Difference
B. boops	F vs TW	14.55 vs 15.53	0.412	No
	F vs TWG	14.55 vs 16.31	0.136	No
	TW vs TWG	15.53 vs 16.31	0.512	No
C. linguatula	F vs TW	15.83 vs 16.91	0.615	No
	F vs TWG	15.83 vs 17.45	0.451	No
	TW vs TWG	16.91 vs 17.45	0.796	No
D. annularis	F vs TW	25.66 vs 27.67	0.251	No
	F vs TWG	25.66 vs 30.78	0.000764	Significant
	TW vs TWG	27.67 vs 30.78	0.0015	Significant

Stomach fullness distribution (%) of the studied species_

Stomach fullness	D. annularis (%)	B. boops (%)	C. linguatula (%)
Empty	58.3 (n = 35)	78.4 (n = 29)	90.3 (n = 56)
Trace	0.0 (n = 0)	0.0 (n = 0)	0.0 (n = 0)
Quarter full	8.3 (n = 5)	2.7 (n = 1)	0.0 (n = 0)
Half full	20.0 (n = 12)	18.9 (n = 7)	0.0 (n = 0)
Three quarters full	1.7 (n = 1)	0.0 (n = 0)	0.0 (n = 0)
Full	11.7 (n = 7)	0.0 (n = 0)	9.7 (n = 6)

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DOI: https://doi.org/10.26881/oahs-2026.1.16 | Journal eISSN: 1897-3191 | Journal ISSN: 1730-413X

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Language: English

Page range: 227 - 238

Submitted on: Apr 9, 2026

Accepted on: Jun 11, 2026

Published on: Jun 30, 2026

Published by: University of Gdańsk

In partnership with: Paradigm Publishing Services

Publication frequency: 4 issues per year

Keywords:

Fulton’s condition,

internal organ,

gonadosomatic index,

weight-based estimations

Related subjects:

© 2026 Hasan Cerim, Özgen Yilmaz, Sercan Yapici, İsmail Reis, Ozan Soykan, Bahadır Önsoy, Anıl Gülşahin, Ferhat Yalgın, published by University of Gdańsk
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

Volume 55 (2026): Issue 2 (June 2026)

Effects of stomach content and gonad mass on length–weight relationships and condition indices in fish species with different body shapes

Figures & Tables

Figure 1

Figure 2

Figure 3

Figure 4

LWR parameters for each species under different weight definitions_

Sample size and morphometric characteristics of the studied fish species_

Pairwise comparisons of Fulton’s condition factor (K) among different weight definitions for each species_

Paired comparisons of mean body weights (F, TW, and TWG) across species_

Stomach fullness distribution (%) of the studied species_

Paradigm

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