In May 2023, oceanic and atmospheric anomalies indicated El Niño conditions in the eastern Pacific, followed by coral bleaching in coral communities and reefs of Huatulco. We conducted surveys and sampled coral reef communities from late June to mid–August of 2023 to evaluate the intensity and extent of the changes associated with the warming event. From January of 2023, Huatulco experienced positive sea surface temperature (SST) anomalies; however, beginning in June, the high-temperature anomalies became extreme (>31 °C; ~2 °C above historical records). These high temperatures resulted in extensive coral bleaching in middle–late June and mortality from middle–late July (>50–93%). In addition, the area experienced significant reductions in echinoderm abundance and fish biomass. In 2023, severe bleaching affected coral systems in the Central Mexican Pacific, Gulf of Mexico, and Mexican Caribbean, making this the most devastating marine heatwave event, simultaneously impacting coral reefs across Mexico’s Pacific and Atlantic coasts.

One of the problems that arose from the meetings of the Barcode in Mexico project was the urgency of having a method in which Mexican authorities could trust for detecting shark finning. This study examined DNA barcoding as a method to identify 14 dried shark fins confiscated by the Mexican Government in two exportation shipments in Mazatlán and Manzanillo ports. Fins were DNA barcoded using the COI mitochondrial gene and provided matching sequences of six species: Prionace glauca, Carcharhinus falciformis, Carcharhinus limbatus, Alopias pelagicus, Mustelus henlei and Rhizoprionodon longurio. There is no information on DNA barcoding sharkfin trade in the Mexican Pacific and this is the first group effort with Mexican Government Agencies for the conservation of sharks.

We present the first record of the fish Leptophilypnus guatemalensis Thacker & Pezold, 2006 (Gobiiformes: Eleotridae) in the state of Chiapas, México, within the Grijalva–Usumacinta basin. Morphological and morphometrical data of 20 specimens from three localities are given.

Zameus squamulosus is a somniosid shark with a patchy world-wide distribution that has been reported throughout the Atlantic, Indian, western, north, central and south-eastern Pacific Oceans. In the Northern Gulf of Mexico Zameus squamulosus is occasionally captured by longlines in deep waters off the coast of Florida, but until now there were no records of the species in the Southern Gulf of Mexico. Four specimens of Zameus squamulosus were collected in 2004 and 2009 on the continental slope of the Gulf of Mexico. Collections were made at depths of 698 m and 701 m. These specimens constitute the first records of this species for the southern Gulf of Mexico and, as they were captured with bottom associated trawls, we infer that this species is more commonly found at the bottom ocean.