Underwater clam rental sites are located and used to produce hard clams of all sizes from small clams to gills. Clam production or aquaculture can be a risky business due in part to unwanted marine intruders. Among them, subtle and very mobile rays.
The Indian River Lagoon is one of the main sites used for hard clam (Mercenaria mercenaria) farming operations along Florida’s Atlantic coast. Clam fishermen anecdotally report seeing rays in clam leases and suspect that their interaction could damage aquaculture equipment and crushed clams. After all, some species of rays are equipped with powerful jaws and plate-like teeth that make them highly efficient miners.
Inspired by clammer’s reports, researchers from Florida Atlantic University’s Harbor Branch Oceanographic Institute and collaborators used passive acoustic telemetry to measure interactions between two highly mobile animals, white eagle rays (Aetobatus narinari) and cownose rays (Rhinoptera spp.) on a lease of oysters. . and four other Sebastian sites, including the Sebastian Inlet and the mouth of the St. Sebastian River.
Because visual observations can be difficult and unpredictable, this technique enabled the researchers to observe tagged rays in the wild over a two-year period.
“We wanted to understand how often and when stingrays visit clam leases, how long they stay there, and whether it’s seasonal or year-round,” said Matt Ajemian, PhD, senior author, associate research professor and director of the study. From the Fisheries Ecology and Conservation Laboratory at FAU Port Branch. “We tagged it and put it on its way and recorded 17,014 unique visits to leases derived from 38 different rays.”
Study results published in Plus one, offering both good news and bad news to the speakers. The rays have spent more time at the clam rental locations than has been reported or suspected, but that’s not necessarily where they like to hang out. For example, the white eagle ray spent only 6.2% of its time near clam rental sites and the cownose ray 13.2%.
Predicting when and when stingrays will visit clam leases has also been complex because it depends on the species, time of day, season, and even certain environmental conditions. Although used less frequently when compared to other reference receiving sites, both types of rays showed longer visits at clam rental sites than some of the sites considered and were periodically monitored within clam rental areas for extended periods of time.
The longest continuous durations in the northern and southern clam rentals were 387.5 minutes and 207.1 minutes, respectively. This shows that rays can stay within these areas for hours at a time, making it more likely that they will interact with clam rentals and possibly hunt for them.
Brianna Cahill, author of the interview, said: “Since 84 percent of all visits were from white eagle rays and their visits were much longer at night, this information suggests that the observed interactions with clam leases are likely to be underestimated, given that Most oyster operations happen during the day.” , a graduate of FAU Harbor Branch Marine Sciences and Oceanography, and a research technician at Stony Brook University.
“The results of our study justify the need to continue monitoring mobile predators in the area, including more studies to assess their behaviors such as foraging at clam rental sites.”
Cownose rays and white eagle rays have different migration patterns, but either way their tendency to move may limit their impact on interlopers.
“Another good news for clam lovers is that stingrays did not use clam rental sites year-round, and their visits varied seasonally, with far fewer spottings and visits during the summer months,” Ajemian said. “This suggests that clams only need to deploy protections against predators, if necessary, for part of the year.”
Findings from the study also highlight the need to understand whether clam leases are located within the rays’ natural foraging habitat and whether rays actively interact with clam leases or whether they are attracted to other organisms nearby.
“It is possible that rays feed on other organisms attracted to clams at clam rental sites, as bivalve aquaculture farms are known to alter community structure and attract a wide variety of predatory snails, which may be an alternative attraction,” Cahill said. Cownose ray and white eagle match their diets.”
Brianna V. Cahill et al, Visitation patterns of two medium radial hatcheries in oyster aquaculture leases at Indian River Lagoon, Florida, Plus one (2023). DOI: 10.1371/journal.pone.0285390
the quote: Crushed Clams, Roaming Rays: Acoustic Tags Reveal Predator Interactions (2023, May 15) Retrieved May 15, 2023 from https://phys.org/news/2023-05-05-clams-roaming-rays-acoustic-tags. html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without written permission. The content is provided for informational purposes only.