# Molecular identification based on mtDNA analysis of commercial crustaceans in the coastal Amazon: exotic species, cryptic diversity, and implications for sustainable fisheries in northern Brazil

## TL;DR

This study uses DNA analysis to identify crustacean species sold in markets in northern Brazil, revealing hidden biodiversity and exotic species that could impact sustainable fishing.

## Contribution

The study reveals cryptic diversity and exotic species in commercial crustaceans using mtDNA analysis, highlighting implications for sustainable fisheries.

## Key findings

- Molecular analysis identified 15 crustacean species, including six exotic and three recently described species.
- Two distinct lineages of Penaeus monodon were documented along the Brazilian coast.
- Generic market labels obscure biodiversity, threatening sustainable fishery management.

## Abstract

Located around the Caeté River estuary, the municipality of Bragança is one of the primary fishing hubs in the region. Several high-value crustacean species are intensively harvested in this area and are commonly sold at open-air markets. However, fishery products are often labeled with generic trade names, which hinders accurate species identification and conceals the true diversity of the exploited species.

Therefore, we conducted the molecular identification of crustacean species sold in Bragança. Samples were collected during two periods: from February to August 2017, and from September 2021 to May 2022. A total of 137 samples were analyzed, including 120 obtained from markets and 17 collected from the wild. Specimens were first identified morphologically, and two regions of the cytochrome c oxidase subunit I (COI) gene were amplified for molecular identification. Genetic analyses included haplotype determination, Basic Local Alignment Search Tool (BLAST) comparisons, phylogenetic tree construction, and species delimitation approaches.

We obtained a dataset comprising 16 commercial names and 151 DNA sequences, including 38 sequences from region I (the barcode region) and 113 sequences from region II of the COI gene. A total of 15 crustacean species, belonging to seven genera and five families, were identified. Six of these species were classified as exotic, and three were recently described in the scientific literature. Additionally, we documented the occurrence of two distinct lineages of Penaeus monodon along the Brazilian coast. Molecular species delimitation tools effectively identified all sampled taxa and revealed underestimated levels of biodiversity due to the use of generic commercial names. This issue poses a potential threat to the long-term sustainability of fishery resources and commercial fishing in northern Brazil, as it leads to biased qualitative and quantitative assessments of fishery products.