The control of invasive species is of major importance for ecological conservation, and there is a need for more effective techniques and approaches to control these species, especially in open habitats. Two types of activities were conducted to control the population of largemouth bass (Micropterus salmoides) in Lake Izunuma-Uchinuma, Japan. The first activity was a lake wide catch using set nets deployed all along the lakeshore beginning in 2001. The second activity, beginning in 2004, focused on catches during the spawning season over spawning sites, distributed along lakeshore segments with sandy substrates. The efforts of both activities were similar (involving about 140 people/year) (Fig. 1). From 2001 to 2003, the catch per unit of fishing effort (CPUE) of largemouth bass using set nets increased; however, CPUE decreased dramatically after catches at the spawning sites started (Fig. 2). The numbers of nests spawned, larvae, and adults of largemouth bass also decreased after the start of spawning site catches. In 2010, the CPUE of other fish species, whose numbers had decreased due to predation by largemouth bass, recovered to the same number as before the expansion of largemouth bass (Fig. 2). Capturing largemouth bass at the spawning sites was an effective approach to controlling this species and conserving fish communities in the lake.

Fig. 1. Volunteer people "Bass Busters" eradicating the blackbass checking the artificial spawning bed (left) and sweeping the bass larvae/juveniles by scoop net (right).

Fig. 2. Stock trends in the blackbass (left) and small cyprinid fish (right). The bass declined since 2004 when reproduction suppression started (1). Small cyprinid fish stock collapsed because of the bass predation (2), but suddenly recovered around 2009 in response to the bass eradication activities (3).

Journal
Management of Biological Invasions 12:997–1011

Doi
10.3391/mbi.2021.12.4.13