Length–weight relations (LWRs) were estimated for ten freshwater fish species such as gin-buna, Carassius langsdorfii Temminck et Schlegel, 1846; lake minnow, Rhynchocypris percnura (Pallas, 1814); Siberian loach, Barbatula toni (Dybowski, 1869); Japanese smelt, Hypomesus nipponensis McAllister, 1963; masu salmon, Oncorhynchus masou (Brevoort, 1856); rainbow trout, Oncorhynchus mykiss (Walbaum, 1792); whitespotted char, Salvelinus leucomaenis (Pallas, 1814); ninespine stickleback, Pungitius pungitius (Linnaeus, 1758); hana-kajika, Cottus nozawae Synder, 1911; and a species of goby Rhinogobius sp. Specimens were collected once a month except in the snow season from the Abashiri River basin, eastern Hokkaido, between June 2007 and November 2011. Fishes were captured by an electrofishing device (Smith–Root Inc., Model 12-b). The estimated allometric coefficient b values ranged from 2.790 (ninespine stickleback) to 3.294 (hana-kajika), and r² values ranged from 0.772 (lake minnow) to 0.994 (goby). All the LWRs were highly significant, with P < 0.001. Besides, the study provides the first estimates of LWRs for the Siberian loach, Japanese smelt, masu salmon, whitespotted char, hana-kajika, and the goby.

LWRs, gin-buna, goby, lake minnow, ninespine stickleback, hana-kajika, Siberian loach, rainbow trout

Length–weight relations (LWRs) are important for morphological comparisons between different congeneric species and populations from different geographical areas (Herath et al. 2014; Panda et al. 2016; Roul et al. 2017a, 2017b, 2018; Tran et al. 2021). Several freshwater fishes inhabit the Abashiri River basin in Hokkaido. However, the species’ primary biological parameters, such as LWRs, have been poorly studied or have not been studied at all. Hence, the presently reported study aimed to provide the first estimates of LWRs for gin-buna, Carassius langsdorfii Temminck et Schlegel, 1846 (Cyprinidae); Siberian loach, Barbatula toni (Dybowski, 1869) (Balitoridae) (Figs 1 and 2); Japanese smelt, Hypomesus nipponensis McAllister, 1963 (Osmeridae); masu salmon, Oncorhynchus masou (Brevoort, 1856) (Salmonidae); whitespotted char, Salvelinus leucomaenis (Pallas, 1814) (Salmonidae); hana-kajika, Cottus nozawae Synder, 1911 (Cottidae) (Figs 3 and 4); and a goby Rhinogobius sp. (Gobiidae). In addition, this study was intended to provide a new estimate of LWRs for alien rainbow trout, Oncorhynchus mykiss (Walbaum, 1792) (Salmonidae), exploited in eastern Hokkaido, Japan, and new estimates of LWRs for lake minnow Rhynchocypris percnura (Pallas, 1814) (Cyprinidae) and ninespine stickleback Pungitius pungitius (Linnaeus, 1758) (Gasterosteidae) inhabiting Asia.

The fishes were collected once a month except in the snow and snow-melt season from June 2007 to November 2011, from Abashiri River basin (i.e., Abashiri River, Horokama-hashiri stream, Kemichappu River, Chimikeppu River, and Tsubetsu River; 43°28′–44°01′N, 143°48′–144°16′E). All fishes were captured by an electrofishing device (Smith–Root Inc., Model 12-b). Fishes were measured in the field after being anesthetized by the clove oil (Anderson et al. 1997). In gin-buna, lake minnow, Japanese smelt, and salmonid fishes the fork length (FL) was measured while in other fishes the principal measurement was the total length (TL) and a fish measuring board with 0.1 cm accuracy was used. Total body weight (BW) was determined by an electronic balance with 0.1 g accuracy.

The length–weight relations (LWRs) for all species were calculated using the equation

log(BW) = log(a) + b log(FLorTL)

where BW is the total body weight [g], FL is the fork length [cm], TL is the total length [cm], log(a) is the intercept related to body form and b is the coefficient indicating allometric growth. The parameters of a and b were estimated by a simple linear regression after logarithmic transformation of length and weight data. Extreme outliers were removed from the regression analysis by performing a log-log plot of the length–weight pairs (Froese 2006). The 95% confidence interval (CI) of parameters a and b and coefficient of determination (r²) were estimated.

The details on length–weight relations (LWRs) of all species are given in Table 1. All the LWRs showed highly significance levels (r² > 0.772, P < 0.001). The formula of LWRs were estimated to be BW = 0.0213FL^2.9353 for gin-buna, BW = 0.0139FL^2.9953 for lake minnow, BW = 0.0076TL^2.9797 for Siberian loach, BW = 0.0089FL^2.8731 for Japanese smelt, BW = 0.0106FL^3.0397 for masu salmon, BW = 0.0117FL^2.9970 for rainbow trout, BW = 0.0121FL^2.9424 for whitespotted char, BW = 0.0119TL^2.7901 for ninespine stickleback, BW = 0.0071TL^3.2937 for hana-kajika, and BW = 0.0063TL^3.2860 for Rhinogobius sp.

Figure 1. 

Siberian loach, Barbatula toni collected from the Abashiri River, Japan.

Figure 2. 

Siberian loach, Barbatula toni collected from the Kemichappu River in the Abashiri River basin, Japan.

Figure 3. 

Hana-kajika, Cottus nozawae (16.3 cm TL, 72.7 g) collected from the Chimikeppu River in the Abashiri River basin, Japan.

Figure 4. 

Hana-kajika, Cottus nozawae collected from the Abashiri River, Japan.

In addition to the fishes mentioned in the results, the following species were collected during the investigation: lampreys (especially ammocoetes larva), Lethenteron reissneri (Dybowski, 1869) and Lethenteron camtschaticum (Tilesius, 1811), and redfins, Pseudaspius hakonensis (Günther, 1877) and Pseudaspius sachalinensis (Nikolskii, 1889), these were difficult to identify in the field and were excluded from this study.

This study was the first report to determine LWRs of Siberian loach, Japanese smelt, masu salmon, whitespotted char, hana-kajika, and Rhinogobius sp. These LWRs were not found in the FishBase (Froese R, Pauly 2022) except for Russian sea-run form of masu salmon. However, Kato (1992) reported the LWR of whitespotted char in Japan; the formula was BW = 0.01389SL^3.0181, where SL is the standard length. Besides, Kato (1991) reported the LWR of subspecies of masu salmon, O. masou ishikawai in Japan; the formula was BW = 0.00220SL^3.66. Both reports using SL were not directly comparable to this study’s results using FL. On the other hand, there are some reports of the LWRs of alien rainbow trout, Oncorhynchus mykiss, in Europe and western Asia (Esmaeili and Ebrahimi 2006; Erguden and Goksu 2008; Verreycken et al. 2011), but there has been no report from eastern Asia. In addition, the LWRs for lake minnow and ninespine stickleback were studied at Lake Baikal in Russia (IGFA 2001) and Lake Superior in the USA (Devine 2002), respectively. These LWRs of this study were the first records in Asia. Furthermore, since the LWRs of gin-buna were recorded from only one individual (IGFA 2001), the results of this study enriched the database. As for the goby, its species identity has not yet been determined, and according to Nakabo (2013), it is probably a species included in Rhinogobius kurodai (Tanaka, 1908), but R. kurodai is not listed in FishBase. These results that provide primary data for further biological research will be useful for fishery conservation in the Abashiri River basin.

We would like to express our gratitude to Yoshiyasu Machida, Yukichi Ohyama, Takufumi Tohyama, Atsumi Nakano, Yuto Takeuchi, Ryota Hashimoto, Yutaro Sera, Takenori Kayaba, Yaoki Tei, Takuma Saito, Yuichiro Yamauchi, Tomohiko Kamigama, the late Kotaro Yano, and all the people who cooperated in this study. We thank the editor, Dr Rodolfo Reyes and the anonymous reviewers for their fair review of this paper and for their helpful suggestions.