Rucha Karkarey is a research scholar with the Oceans and Coasts Programme at NCF. She has spent the last seven years stalking groupers (these really interesting fish) underwater, trying to understand how they are coping with climate-change. She took over our Instagram for a week, and shared stories about curious behaviours of groupers from her fieldwork in the Lakshadweep archipelago. We’re sharing them with you in this blogpost. To follow us on Instagram, click here!
Have you heard of groupers? They are the leopards of the sea! These formidable predators feed on smaller reef fish and are masters of camouflage.
Like the leopard, they are ambush predators. They stealthily stalk their prey or remain very still for the opportune moment when unsuspecting prey comes close enough. They then attack with a sudden burst of energy!
Groupers, like this stunning coral hind, are mostly found in coral reef habitats that have a mosaic of caves, columns, cracks and crevices—structures which they can use as shelters from larger predators like sharks, or to hide from prey to ambush them.
Most grouper species are long-lived. The giant grouper—one of the largest groupers—reportedly lives for over 60 years! But don’t let size fool you, even the smallest of groupers (20 cm) can live for as long as 20 years!
Many species of groupers, like the squaretail grouper, show an interesting mating strategy. When individuals from nearby reefs are ready to reproduce, they come together at a particular site, at a particular time (usually coinciding with some moon phase), to release their eggs and sperm. This is called spawning. Fertilization takes place in the water column and these fertilised eggs are dispersed by ocean currents to the deep open ocean where they develop into larvae over 2-3 three weeks. Once the larvae are big and competent enough, they swim to nearby coral reefs and populate them. After a couple of days of spawning at the aggregation site, the groupers return back to their own home ranges. These events are called spawning aggregations.
Many grouper spawning aggregations take place like clockwork—each aggregation forms at the same site and time through the year.
Scientists have long wondered what lead to the evolution of such a bizarre ‘community’ mating strategy. One of the theories suggests that because most resources in the ocean are spread over vast areas, are disconnected and unpredictable, it is difficult for solitary individuals to find mates (apparently there isn’t such a thing as ‘too many fish in the sea’!). Therefore, by forming these regular aggregations, most individuals are easily able to find mates and they can cherry-pick their mates too!
Groupers come in all sizes—from the smallest leopard hind (20 cm) to the largest Goliath groupers (larger than 1.5 m). But at all these sizes, they are just as fierce.
All of the species have a similar bulky body shape, with a large head, a large mouth with thick lips, downturned as if sporting a perpetual scowl.
In the beautiful coral reefs of the Lakshadweep archipelago, we have recorded 33 different species of groupers! These are a few of them.
My favourite among groupers is the squaretail grouper. “Of all the beautiful fish on the reef in Lakshadweep, why this frowzy creature?” you may ask. Well, here are my top three (of many many) reasons why I love this fish:
#1 Because it is a protogynous hermaphrodite, which means it is a sex-changing species—beginning its life as a female, it transforms into a male at a later stage, once it has reached a certain size!
Infact, the reef is rife with gender-benders, several fish species undertake male-females transitions, female-male transitions, and some even show reversible sex-change through their lives !
#2 Squaretail groupers form large spawning aggregations and one of the largest in the world was recorded here in Lakshadweep in early 2012!
#3 They have the most wondrously scandalous sex-lives! In this high-density aggregation in Lakshadweep, we recorded a bizarre sexual pattern. Small female squaretail groupers engage in rampant shoal spawning with eager large males. When they grow into large females, they mate sedately with a single male, away from the romping of the shoal. These large females then transform into small males, who can only hope for a single female to mate with at the aggregation site. Finally, these small males grow into large males, who can enjoy all the benefits of the shoal once again!
So, these groupers can go from: Small female—>Large female—>Small male—>Large male in the course of their lives! How fascinating is that!
Because of the predictable nature of groupers—they come together in large aggregations to spawn each year at the same time and place. As you can imagine they become highly attractive targets for commercial fishermen. By fishing at aggregation sites, fishermen can obtain bumper catches of fish in little time and with little effort. As a result, spawning aggregations wherever known, are almost always overfished.
Understandably then, when a major reproductive component of the population is fished, fewer babies feed into the next generations. This is how an aggregating species dramatically begins to decline in just a few years.
Up until 2013, there used to be relatively low fishing pressure on Lakshadweep’s reefs as offshore tuna was the economic mainstay of fishermen.
However, since 2013, with tuna stocks fluctuating and becoming increasingly unpredictable, fishermen started turning towards fishing for nearshore coral reef fish, which was a far more predictable resource.
Predatory fish like sharks, groupers and snappers, usually become the first targets in an emerging reef fishery. And when commercial fishing starts overlapping with fish spawning aggregations, as it did with the once ‘pristine’ squaretail grouper aggregation in 2013—the damage can be irreversible.
Without proper management and regulation of this burgeoning reef fishery, the squaretail grouper spawning aggregation hardly stood a chance, and were severely threatened.
Groupers have not previously been a commercial or preferred food species for locals in the Lakshadweep.
When they learnt that this is the largest squaretail grouper aggregation in the world, they were filled with a sense of pride.
Our team spoke to the local islanders about the potential danger to groupers from unregulated aggregation-fisheries in 2013, and they immediately came forward to protect these spawning aggregations.
In 2013, after learning of the threats facing the squaretail grouper (they call it the ‘kokka chammam’ or ‘spotted grouper’), the Panchayat, after numerous consultations with local fishermen drafted a letter to the Fisheries Department of Lakshadweep, requesting for the establishment of seasonal fishing closures during the spawning period.
The Lakshadweep administration responded in a timely manner to declare a seasonal fishing closure on the coral reef during the squaretail grouper spawning season between December-April (which is when these groupers spawn) in the island of Bitra. The fishing closure is binding for five days of the month when the groupers are aggregating to spawn on the coral reef. For the remaining days, fishing activity can resume as usual. During this fishing closure, the lagoons are open to fishing so that people can meet their daily fish requirements.
Since that historic moment in 2014, the fisheries order has been repeated every year, for four years with high compliance.
The island people have turned into guardians of the squaretail grouper, ensuring that no fishing takes place on the coral reef during the closure periods.
Despite all these efforts, the squaretail grouper is not completely out of danger yet.
Our team continues to track a frightful trend of decline in the squaretail grouper aggregating population in the Lakshadweep.
This is mainly because of the overall increase in reef fishing pressure in the archipelago and the changing aspirations of Lakshadweep fishermen who are growing more interested in the export trade.
The seasonal fishing closure appears to have redistributed the fishing effort, such that fisheries are now targeting groupers during non-aggregation periods and in locations other than where these groupers aggregate to spawn.
The groupers who are safe during the spawning period thanks to the fishing closure, are potentially still being harvested once they make their way back to the reef after spawning.
Apart from seasonal fishing closures to protect spawning aggregations, we need measures that directly control what and how much is being harvested—either through having a regulations on how many groupers can be caught or what size individuals can be caught.
This seems like a daunting approach to design and implement, but in an effort to conserve their beloved ‘kokka-chammam’, the Islanders have an infectious sense of hope and willingness.
In the coming years we hope to better understand the sustainable limits to harvesting fish like these sex-changing groupers, which are ecologically and economically important coral reef fish.