Discovering the fish fauna of a lagoon from the southeast of the Yucatan Peninsula, Mexico, using DNA barcodes

Abstract

Background: Aquatic ecosystems in the tropics are typically environments with a high species richness of fishes. These systems are also among the most vulnerable in the world, threatening the overall biodiversity of tropical regions. As a first step, it is important to enumerate the species in any ecosystem to promote its conservation. This study aims to inventory the ichthyofauna in the Chile Verde Lagoon, Quintana Roo, on the Yucatan Peninsula, a system fortunately well protected in Mexico, based on faunal surveys backed up with mtDNA barcodes.

Methods: We collected larvae, juveniles, and adults of fishes in the lagoon with a variety of sampling gear targeting various life stages. Species were identified using both morphology and DNA barcodes. The abundance of species and ichthyoplankton biomass (wet weight, suction technique) were calculated from 43 samples.

Results: We collected 197 adult and juvenile fishes and 3,722 larvae, of which 306 specimens were DNA-sequenced with a success rate of 96.7%. We identified 13 families, 24 genera, and 27 species in our inventory. The species number was estimated to comprise 75% of the potential total richness using the Chao 1 richness estimator. Clupeids and gobiids accounted for 87.9% of the total abundance of fishes, and, together with cyprinodontids, also accounted for the highest ichthyoplankton biomass.

Conclusion: Adult and juvenile fishes were identified by morphology and meristic values, however larvae required DNA barcoding to identify species. The high biomass and abundance of larvae of clupeids, gobiids and cyprinodontids suggests that the Chile Verde Lagoon may be important for reproduction of these species in the region. Microgobius microlepis, a marine goby species, is reported for the first time in an inland oligohaline system. This study provides a basis for future environmental assessment and biomonitoring of the Chile Verde Lagoon in the Yucatan Peninsula of Mexico.

Keywords: Biodiversity; Diversity; Epicontinental fishes; Fish larvae; Freshwater; Quintana Roo.

Figure 1. Location of Chile Verde Lagoon in Yucatan Peninsula and sampling points.

Figure 2. Simplified neighbor-joining tree showing the species identified using the COI gene.

Figure 3. Fish species richness from four months of sampling in Chile Verde Lagoon (February to May 2022), with extrapolation to 30 samples.

For the construction of the accumulation curve, data were grouped into light trap samples, standard plankton net samples, and adult sampling gear for five sampling events.

Figure 4. Venn diagram comparing the richness collected by art sampling.

The number in bold indicates the species collected, the number in brackets is the abundance, and the number in the overlapping area indicates shared species. It should be noticed that littoral and limnetic light traps are together.

Figure 5. Developmental stages of M. microlepis larvae captured in the Chile Verde Lagoon.

(A) Larvae in preflexion; no fin rays. (B) Larvae in flexion; 1st dorsal fin rays incipient, 2nd dorsal and anal fin rays developed. (C) Settlement stage; fully developed fin rays.

Figure 6. Relationship between abundance and biomass.

(A) The blue area shows samples dominated exclusively by Gobiids and Clupeids; the intersection of green areas shows samples dominated by Gobiids, Clupeids and Cyprinodontids. (B) Behavior of ichthyoplankton biomass (dashed line) and abundance (solid line) during the sampling period. All standard deviations of ichthyoplankton biomass from each sampling event were <0.02%.