NASSAU, BAHAMAS — New research recommends banning all industrial and recreational parrotfishing and establishing complete no-take policies inside all Marine Protected Areas (MPAs) to forestall further declines within the species largely liable for stopping algae from overtaking coral reefs in The Bahamas.
The new study published within the journal, Diversity is authored by Dr Krista Sherman, Maya Gomez, Thomas Kemenes, and Dr Craig Dahlgren of the Perry Institute for Marine Science (PIMS).
Dubbed “nature’s lawnmowers”, parrotfish are vital for maintaining resilient coral reefs that protect coastlines, provide food, and support livelihoods. Nevertheless, in The Bahamas, parrotfish are increasingly being targeted and up to now, no fishery regulations have been implemented.
Using fish data, collected over nine years of reef surveys, marine scientists examined the status of parrotfish across different reefs around New Windfall and Rose Island. Their goal was to find out whether parrotfish populations have modified over time and if these changes are related to increased fishing pressure.
PIMS scientists found “a 59 percent decrease in the typical density of parrotfish overall, with significant declines occurring in three parrotfish species: Striped, Redband, and Greenblotch.”
“Notably, we also found significant changes in parrotfish size composition over time, with a shift to smaller size fish and the entire loss of enormous adults, greater than 40 cm (15 inches) across all 26 reef sites. This finding has vital implications for not only the survival of parrotfish populations but additionally their ability to keep up key ecosystem processes on Bahamian coral reefs,” said Dr Sherman, lead writer, and PIMS’ senior scientist.
Researchers fear that significant declines in parrotfish populations on top of threats reminiscent of coral bleaching, oil spills, hurricanes, and stony coral tissue loss disease, may further stress local coral reefs.
In reality, data have shown macroalgal coverage on reefs around New Windfall is growing. Macroalgae, or large aquatic photosynthetic plants, covered anywhere from 18 to 38 percent of coral reefs between 2011—2014. By 2019, that number had jumped to 42 percent.
“Parrotfish populations in The Bahamas have typically been amongst essentially the most abundant within the Caribbean, but these latest results display around 58 percent of the reefs surveyed are actually lower than regional values, with significant declines occurring in a number of parrotfish species,” said Dr Sherman.
“To make matters worse, large parrotfish are known to be more practical at grazing, that is, removing macroalgae than smaller fish. So, the loss of those large herbivores has implications for the condition or health of coral reefs habitats.”
Along with coral restoration efforts, researchers say responsible fishing practices are needed to keep up a healthy distribution of parrotfish if the nation desires to protect its coral reefs and the livelihoods of fishers that depend upon them.
Other countries within the Caribbean, including Belize, Bonaire, and Turks & Caicos, have already introduced fishery regulations – size limits, bans or catch limits – to conserve their parrotfish populations.
“Our results highlight the importance of monitoring and emphasize the urgency of implementing science-based strategies to sustainably manage the fishery and protect these ecologically essential herbivores, that are vital components of coral reefs,” Dr Sherman noted.
PIMS researchers say the study provides a benchmark to observe potential changes to parrotfish populations and will help measure the effectiveness of any new fishery regulations.
