Angling to estimate the density of large round goby (Neogobius melanostomus)

We introduce an angling technique for estimating the density of the round goby (Neogobius melanostomus). Sampling is conducted from a boat that is securely anchored in a randomly selected site. By taking advantage of the aggressive nature, small size, and limited home range of the round goby, two anglers are generally able to deplete the local aggregation of gobies in a 20 min period. Density is estimated using a depletion curve and reliable estimates were produced in 76% (52/68) of field trials where round gobies were present. Relative abundance was estimable for 100% of trials. An experimental procedure indicated that refuge status (gravel or rock), density, or temperature had no effect on round goby capture efficiency using this technique (p > 0.05 in all cases). Angling is a relatively inexpensive and simple technique that is useful in providing a relative measure of the density of gobies larger than 50 mm TL, and is especially useful in situations where round gobies can evade capture or detection by other methods. Although most appropriate for sampling species with similar behavioural characteristics to the round goby, this novel sampling procedure also demonstrates that angling continues to be a useful tool for assessing fish populations.