Evaluating the performance and management of artificial reefs using artificial reef multimetric index (ARMI)

Abstract

Artificial reefs (ARs) have become an important tool to increase the ichthyofauna associated with artisanal and commercial fishing. Integrated evaluations of ARs are necessary to comprehend the condition and benefits of these structures. Multimetric indices (ARMIs) were developed to evaluate fish assemblages associated with artificial structures and to assess the efficiency of the AR compared to control area (CA). The AR global ranking index (ARMIr) and AR local effect index (ARMIe) include 16 metrics that represent four broad levels of the fish community: structure of fish assemblages, trophic structure, vulnerability and economic importance. Individual metrics were evaluated using a long-term dataset of fish assemblages from the AR and CA in northern Rio de Janeiro, Brazil. Bottom gillnets were used to sample the fish two times per year for 21 years after creating the reef. The ARMIr general score for the AR was 51 out of a possible 100, with scores varying from 38 to 54. The ARMIr general score for the CA was 39 out of 100, with scores varying from 35 to 47. Average ARMIe values were 12% higher for the AR in relation to the CA. Spatial-temporal comparisons of the ARMIr using generalized additive models revealed significant differences between AR and CA. Evaluations of the ARMIe scores revealed that the assemblage structure and economic importance level significantly increased over time in the AR. The proposed indices combine structural and functional levels of fish, providing a robust and sensitive method to evaluate the ecological condition of ARs and adjacent areas. The data contribute to discussions related to ARs management and provides a baseline for defining fish assemblage metrics in assessment of localities with artificial structures.