Length-weight relationships and length-frequency analysis varying with seasons for fish community in the Luanhe River Estuary, Bohai Sea, northern China

Abstract

The Luanhe River Estuary in the Bohai Sea in northern China is an important nursery and good fishing grounds for many marine organisms, including fish. Length-weight relationship （LWR） of fish is an important indicator for the proper fishing and management of fish populations. This study was conducted to obtain LWRs for fish species distributed there. From December 2016 to August 2017 at one-month intervals and from July 2016 to November 2017 at two-month intervals, using crab pots, trawl nets and bottom trawl nets, a total of 7,593 individuals belonging to 32 species in 20 families were obtained and their length and weight were measured. The most abundant species was Chaeturichthys stigmatias （N = 2, 487）. Lengthweight relationships （W = a × Lb） were obtained for the 17 fish species for which sufficient individuals were available for statistical analysis. Linear regression of log-transformed data was highly significant for all analysed species （p ＜ 0.05）, with LWR slope b values ranging from 2.57 for Synechogobius ommaturus to 3.66 for Engraulis japonicus. The b values of 50% of the total species ranged between 2.95 and 3.30. The LWR information could be used to manage fish stocks not only in the Luanhe River Estuary but also in other estuarine fisheries.