The Bay of La Paz is the largest coastal water body in the Gulf of California with an approximate area of 2,635 km2. It is situated on the southeastern coast of the state of Baja California Sur, 180 km north of the mouth of the Gulf. While the Bay of la Paz isn’t in itself a marine protected area, it does incorporate a number of areas that hold some form of protection under national law. The area to the south of the bay encompasses a protruding sandbar known as the El Mogote, a marine refuge for whale sharks with an active management plan for ecotourism activities with this species.

Project overview:

The Bay La Paz has diverse marine megafauna, such as sharks, turtles, whales, dolphins, and sea lions. It is also a nursery area for several species of sharks, like the sharpnose, scalloped hammerhead and whale sharks. Shark nurseries are in coastal areas, where females give birth to their pups. These areas play the role as refuge for the neonates and juvenile sharks, where there is abundance of prey and protection from predators. The Bay of La Paz is also home to our whale shark monitoring program. This species is known to seasonally aggregate in the coastal waters of the Bay.

Overarching goals:

- Understand seasonality and population size of newly born (neonates), juveniles, pregnant females of sharpnose, scalloped hammerhead and whale sharks in the Bay of La Paz

- Determine the population dynamics, seasonality and site fidelity of these sharks in the Bay of La Paz

- Characterize the feeding behaviors of the species through fine-scale data logging and the application of machine learning algorithms

- Understand the habitat use and migratory movements of the species through acoustic and satellite telemetry techniques

- Determine the dietary preference of whale sharks in the Bay of La Paz and the importance of different prey items

Activities:

1. Conventional tagging. Spaghetti tags are placed on sharpnose and scalloped hammerhead sharks. This type of tag is affixed to the base of the first dorsal fin to estimate the population size through recaptures.

2. Ultrasonic tagging. We affix ultrasonic transmitters on different species of sharks. We use ultrasonic tags, which emit a specific code that is recorded by acoustic receivers (listening stations). The transmitters are placed externally in the base of the dorsal fin with a Hawaiian sling used for spearfishing by SCUBA or free divers. Transmitters are also put internally in the intraperitoneal cavity through capture and a small surgery.

3. Listening stations. The stations consist of an underwater receiver VR2W (Vemco Ltd) that records acoustic pulses from the ultrasonic tags in a maximum range of 500 m. The stations are placed at depths between 20 and 40 meters at shark aggregation sites. We have 10 listening stations distributed in the Bay.

4. Satellite tagging. Satellite transmitters are designed to track the large-scale movements and behavior of fish and sharks. These transmitters are equipped with light, temperature, depth and accelerometer sensors, that either archives data in an onboard memory or transmits during deployment. We are deploying satellite transmitters in scalloped hammerhead sharks.

5. Genetics and isotopic signals. We collect skin biopsies for genetic and isotopic analysis to determine connectivity and habitat preference between the different species and life stages.

Whale shark activities:

1. Photo ID. Unlike many other species of sharks, the skin patterns that juvenile whale sharks exhibit remain unchanged as they mature. Present research techniques by means of photo-identification of the individual skin markings of sharks shows that they can be individually identified from one another, offering a non-invasive approach to investigate population structure of the species. Further information is collected via standard photographic means such as the health and status of the shark, though general observations and injury classification analysis, as well as the association of different marine fauna to whale sharks.

2. Whale shark tagging. The use of external acoustic telemetry coupled with satellite telemetry allows us to understand the fine scale habitat use and the large-scale migratory movements of whale sharks in this region. A wide variety of instruments have been used, such as external towed tags, daily diary data loggers, acoustic transmitters and three-dimensional accelerometers that record a variety of behavioral information.

3. Whale shark diet. Routine sampling in the Bay and its available prey items, together with biochemical studies of the sharks allows us to determine dietary preferences and understand if any differences are apparent with sex or maturity of our sharks. In addition, modern data logging instruments that record fine-scale behaviors of the animals that are attached to sharks aid us to build behavioral models of the different foraging behaviors.

Other institutions participating in this Project:

- Centro Interdisciplinario de Ciencias Marinas-IPN

- Centro de Investigaciones Biológicas del Noroeste

- Instituto de Ciencias del Mar y Limnología, Unidad Mazatlán, UNAM’

- University of California, Santa Cruz

Species under investigation: