Ten years after: a review of squidpop assays to test predation in aquatic habitats

Ten years have passed since the introduction of a standardized methodology for measuring consumption rates by animals in aquatic environments, known as “squidpops”. Its low-cost, easy-to-implement design made it an alternative for studies aiming to compare consumption rates across different scenarios. The objective of this review is to carry out a critical evaluation of squidpop studies over the past 10 years, examining the development and application, and highlighting its strengths and limitations, along with recommendations for its use in future studies. To date, 43 squidpop papers have been published, comprising 48 different studies. These studies have been conducted in different parts of the world, with North America being the region with most squidpop deployments. In general, the original setup was maintained in most studies. Squidpops were used mainly to compare consumption rates across habitats, with the results indicating that squidpop consumption is higher in complex habitats. Consumption was also compared across temperature and salinity gradients and at different latitudes, corroborating the hypothesis that predation is more intense at low latitudes. Since squidpop consumers are mainly small- to medium-sized fishes, and thus prone to being consumed by top predators, the presence of shelter and the absence of large predators often led to an increase in squidpop consumption. A trophic cascade of squidpop consumption is then hypothesized based on direct and indirect variables described in the studies analyzed. Future studies should focus on identifying consumers, primarily by combining the squidpop approach with underwater videos. Despite limitations (non-living, immobile food), squidpops have become a reliable alternative for measuring consumption rates by benthic consumers, providing valuable comparative information from local to global scales for top-down control in aquatic environments.