Accurate resource assessment requires experience in a territorial fish

Although the relationship between resource-holding potential and contest dynamics is well studied, how the value of a contested resource influences aggressive interactions has received far less attention. Questions about how animals assess a contested resource, and whether they can update their assessments of resource value during a contest require additional testing. To address this issue, we conducted a series of experiments using an invasive, territorial fish, the round goby, Neogobius melanostomus. We used this species to investigate the impact of resource quality on contest dynamics, and to test how animals gather information on resource value. First, we found that fish preferred an enclosed shelter (‘high quality’) to an open shelter (‘low quality’). Despite this preference for high-quality shelter, fish fought equally hard for both high- and low-quality shelters in staged resource contests when they had no prior experience with the resource. However, when fish were given prior experience, contests over high-quality shelters began faster and had more aggressive acts than contests over low-quality shelters. Interestingly, when the value of the resource in the contest was switched from their prior experience, the fish seemed unable to fully update their appraisal of resource value, and contest dynamics were not strictly driven by the previous or current resource value. Round goby may therefore have a limited ability to update their appraisal of resource value when engaged in a contest. Together, our findings demonstrate that fish adjust their aggressive effort to reflect resource value, but previous experience with the resource is required to assess the resource efficiently.