Length-weight relationships for 17 fish species in the Luanhe River Estuary, Bohai Sea, northern China

Length-weight regressions (LWR, W = a × Lb) of 17 coastal fish species from the Luanhe River Estuary in northern China are presented in this study. A total of 7354 samples from 11 families were measured and weighed. The slope (b) values for LWR ranged from 2.572 in Acanthogobius ommaturus to 3.6581 in Engraulis japonicus. The median value was 3.114 in Platycephalus indicus, although 50% of the values ranged between 2.9451 to 3.2965 for the entire data set.


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Estuarine areas are extremely important areas in the life cycle of some fish species. 30 These ecosystems provide food, shelter, and spawning grounds for varieties of marine 31 organisms. The Luan River is a sediment-laden water course on the northern shore of 32 Bohai Bay, China [1]. The estuary of the Luan River is a famous fishing ground and 33 nursery area for marine organisms within Bohai Bay. This area is recognized as an 34 important feeding and breeding location for migratory species [2][3][4][5]. 35 Length-weight regressions (LWR) are an important tool for the proper exploitation 36 and management of fish populations[6]. Length and weight data for fish are needed to 37 estimate growth rates, age structure, and other population dynamics [7]. This information 38 is commonly used in the ecosystem modeling approach [8] to calculate the production to 39 biomass ratio (P/B) of different functional groups, taking into account that for more 40 precise weight estimates it is advisable to make use of local values. In addition, LWR 41 allow life history and morphological comparisons between different fish species, or 42 between fish populations from different habitats and/or regions [9]. Biological scientists 43 often estimate fish weight in the field using LWR [10].

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Prior to this study there was LWR data available for fish species in the Luanhe River 45 Estuary and this study provides the first LWR references for 17 fish species from this 46 area. This study aimed to provide information that could be used for the management of 47 the Luanhe River fishery grounds. The LWR data will be made available through the 48 Fishbase Database[11], so that they can be used by other researchers. 49 50

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The field survey was approved by the Institute of Oceanology, Chinese Academy of 53 Sciences. 54 This study was carried out in the Luanhe River Estuary between longitude E 118°5 5 57'-119 09' and latitude N 39 03'-39 15'. The estuary is subject to irregular, semidiurnal length of a single crab pot was 8 m, and five were connected together at the survey 65 station, giving a total length of 40 m. Trawling was carried out at a speed of 2 knots and 66 the mouth of the net was 2.5 m long. 67 After hauling, fish samples were immediately transported to the laboratory in Hebei 68 Provincial Research Institute for Engineering Technology of Coastal Ecology 69 Rehabilitation. Specimens were identified to the species level. Scientific names for each 70 species were checked in Fishbase [11]. The standard length (L) of each specimen was 71 measured to the nearest 0.1 cm using a 30-cm ruler. Fish body weight for all specimens 72 was weighed to the nearest 0.01 g using an electric balance (CR-5000WP, Custom, 73 Japan).

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LWR were calculated using the equation [12]. The relationships = × 75 between the length and weight of the specimens were calculated by least-square linear 76 regressions applied to logarithmic transformed data combined as[13]: 77 log = log + × log 78 Where 'W' is fish body weight (g), 'L' is fish standard length (cm), 'a' is the initial 79 growth coefficient and 'b' is the growth coefficient. The statistical significance level of 80 R 2 was estimated in LWR fitted by least-squares regression. Only extreme outliers 81 attributed to errors in data collection were omitted from the analyses. 82 The application of these regressions should be limited to the observed length ranges. 83 These estimated parameters can be treated as mean annual values for the species in our 84 study. 85 The 95% confidence interval, CI of b was computed using the equation: Where is the standard error of b. 88 89

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A total of 7354 individuals belonging to 17 species (11 families) were recorded in 92 this study. The species, family, sample size (N), length range (cm) and weight range (g), 93 length-weight relationship parameters a and b, 95% confidence interval for b, the 94 coefficient of determination (R 2 ) are presented in Table 1. Linear regressions of log 95 transformed data were highly significant (P<0.05) for all analyzed species. The most 96 abundant species sampled was Chaeturichthys stigmatias (N=2483). The best represented 97 family was Gobiidae with 4 species recorded. 98 The coefficients of determination (R 2 ) ranged from 0