# First Confirmed Record of a Bull Shark in Lake Gatun, the Freshwater Body of the Panama Canal

## TL;DR

Scientists confirmed the first bull shark in Lake Gatun, a freshwater part of the Panama Canal, raising questions about its migration and potential ecological impacts.

## Contribution

This is the first confirmed record of a bull shark in Lake Gatun, offering new insights into its migration patterns and canal connectivity.

## Key findings

- A bull shark was captured 30 km from the Pacific entrance of the Panama Canal in Lake Gatun.
- DNA and morphometric analysis suggest the shark originated from the Pacific Ocean and may have pupped in low-salinity areas near the canal.
- Recent captures and a video suggest increased potential for Pacific and Atlantic bull shark populations to interact through the canal.

## Abstract

Bull Sharks are circumtropical top predators able to tolerate a wide range of salinity conditions that include freshwater. In several areas of Central America this species is known to migrate upstream in rivers and is commonly found in freshwater. The Panama Canal, an engineered system critical for global shipping, has experienced repeated marine fish incursions into Lake Gatun, the freshwater portion of the system, since it opened over 100 years ago. With increased numbers of species and abundance of these marine migrants into the system it is surprising that no credible reports of Bull Sharks have been made to date. Here we present the first confirmed report of a Bull Shark captured in Lake Gatun, 30 km from the Pacific entrance of the Canal. Analyzing its DNA barcode and vertebral morphometrics and chemistry, we were able to infer the origin (Pacific Ocean), the total length and age (120–150 cm, 2–3 year old) and likely pupping of this shark in low salinity areas adjacent to the Canal. The recent capture of more bull sharks by the artisanal fisher who collected the study shark and a video of sharks at the seaward entrance to the new Pacific locks indicates that there is the potential for increased contact between Pacific and Atlantic Bull Shark populations through the Panama Canal.

The Panama Canal, an engineered system critical for global shipping, has experienced repeated marine fish incursions into its freshwater portion since it opened > 100 years ago. With increased numbers of species and abundance of these marine migrants into the system, surprisingly, no credible reports of Bull Sharks have been made to date. Here we present the first confirmed report of a Bull Shark inside the Panama Canal, 30 km from its Pacific entrance, and analyze the potential implications of this finding.