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Extracting an otolith from the head of a Great Barracuda (Sphyraena barracuda) Photo: Pete Oxford

How old is that fish? You’d be surprised.

Extracting an otolith from the head of a Great Barracuda (Sphyraena barracuda) Photo: Pete Oxford

Extracting an otolith used to age the fish from the head of a Great Barracuda (Sphyraena barracuda) Photo: Pete Oxford


An increasing number of studies are revealing that fish are far older than we ever thought. You may ask why this important: sound management of a fishery requires a good understanding of how quickly (or slowly) individual fish in a species grow, at what age they begin to reproduce, and how long they live. These factors represent some of the most basic biological information required to understand the status of a population and or species, because we need to ensure that enough fish are able to replace themselves before they are removed from the sea. A study that seeks to answer these questions is known as an age and growth study. As great variability in growth occurs across populations and within a same species, age and growth studies should be conducted for every distinct population of a species that is subject to fisheries.

Before an age and growth study can be conducted, we need to figure out how to age the fish. How do we do that? Well, as fish grow, seasonal variation in temperatures cause differences in growth rates, with fish growing more quickly when the water is warmer and food more abundant than during the cooler months. These differences in seasonal growth form annual ‘bands’ in calcified structures within fishes’ bodies, and otoliths are one such type of structure. Otoliths are mineralized structures located in the fish’s inner ear, which enable accurate sensing of body orientation to gravity. By carefully extracting the pair of otoliths from two capsules near the top of a fish’s head, we hold the key to the life history of that individual fish. In order to view the annual bands, and therefore age the fish, a variety of methods may by used, but most involve cutting these delicate structures in half through the center, and counting the bands using a microscope. The fish’s age is then linked to its weight, length, sex and reproductive condition at the time of capture. Once we’ve collected otoliths from hundreds of fish, these data will not only give us the growth rates and ages at maturity for the population, but can indicate important factors such as natural mortality and the species overall risk of over-exploitation by fisheries. Determining the age of fish is a tedious but relatively simple process, and the growth rate of a fish’s body has been found to be generally proportional to the temperature of their environment.


Evan Cuevas measures a barracuda prior to removing the otoliths. Photo: Rachel Graham/MarAlliance


A remarkably recognizable and yet poorly studied species that we frequently encounter during our fieldwork is the great barracuda (Sphyraena barracuda). This charismatic, predatory fish species can often exceed 1 meter (3.3 ft) in length, and in fact can grow as large as 1.8m (5.94ft)! Popular as a food and sport fish, great barracuda are often targeted by fishers throughout the tropics, and surprisingly the fishery is currently unmanaged throughout most of its range. Equally surprising is the lack of scientific studies on this important species. In order to remedy this glaring deficit, we have collected measurements and samples from 290 great barracuda throughout the primary reefs of the MesoAmerican Reef (Mexico, Belize and Honduras), to create the needed age and growth study for this species.

Our study will significantly improve understanding of how great barracuda age and grow, and will provide important information in the development of local, national and regional management strategies for this commonly captured fish. Already we are finding that the fish we see are older than we expected, with barracuda of moderate size easily reaching 19 years of age. This gives us something to think about when assessing whether the populations of a fish we consider common can withstand the increasing fishing effort recorded worldwide.

“We’re gonna need a better BRUV”


“Wait, WAIT…WHAT WAS THAT?… go back… go back…!”. This is a familiar cry when we are reviewing footage from our underwater camera traps. Through this sneaky peep show of sorts we have made countless discoveries of big fish and other marine wildlife and their preferred habitats. And this work has been critical to understand the diversity and abundance of large marine wildlife and reveal hotspots for specific species, notably those threatened with extinction and in more dire need of conservation attention.

Compared to our terrestrial counterparts, we marine conservation scientists often struggle to work with a limited toolkit in our quest to study wildlife. Camera “trapping”, originally developed to capture images or video of rarely encountered terrestrial species and a key component in censuses, has recently exploded onto the marine stage. The miniaturization of technology and vastly reduced costs of underwater cameras, notably the ubiquitous GoPro, has enabled just about anyone to spy on fish. Commonly known as Baited Remote Underwater Video or BRUVs, these installations were developed in the 90s and are now commonly used in shallow marine projects as a non-invasive means of assessing fish diversity and abundance.

With limited means at our disposal and a desire to make the installations as cheap and easy to make as possible we built our first units in 2012 to conduct the first Belize Barrier Reef census of large marine wildlife. Randomly placed on coral fore-reefs, patch reefs and lagoon areas we found several hotspots for sharks, rays, turtles and big snappers and groupers that we have integrated into our conservation strategies. These surveys have notably highlighted Lighthouse Reef Atoll as being Belize’s site with the highest abundance and density of large marine wildlife. Initially built with PVC pipes with a design pioneered by Ben Fitzpatrick, we found that continual breakages forced us to move to metal frames in 2015. Bulky and taking up precious space on the small boats we use for our work, we also found these far too heavy for our incipient deep-water shark work that required us to drop and retrieve BRUVs by hand to over 500 meters.

It was at this point that we declared in a parody of the iconic film Jaws that “we are going to need a better BRUV!”. Cue the sound of trumpets as one of our volunteers, Sam Owen, came to our technological rescue. Self-effacing and incredibly ingenious, a literal Jacques of all trades and staff at the Royal Albert Museum in Edmonton Canada, Sam has helped us to function in several of our project sites by ensuring that our technology works. He took on our “Build a Better BRUV” challenge and created a streamlined, lightweight and collapsible unit that can easily be transported to our various study sites. Recently tested in Honduras, we were thrilled at the ease of deployment and retrieval, and have gained several new fisher ambassadors for the work that we do. And just what did we see you dare to ask? Well…you will just have to stay tuned for that nugget of info. And it’s worth the wait to see what our “box of chocolate” camera traps reveal. We just never know what we’re gonna get on the videos as we push the science and conservation envelope beyond the shallow seas and into the nearly unknown deep-sea realm of our Barrier reef.

How are our fish doing? Monitoring can help answer the question


Exson Flores, a traditional fisher from Honduras, surveys the coral reefs for large fish over the course a transect kilometer. Photo: Rachel Graham/MarAlliance


Significant gaps of information exist globally on sharks and rays, collectively known as elasmobranchs, and this is proving a challenge to conservation efforts. The MesoAmerican Reef region (Mexico, Belize, Guatemala and Honduras) is no exception. Honduras is one of 15 countries worldwide that declared its waters a “shark sanctuary”, which bans shark fishing and the commercialization of their meat and derivatives. Unfortunately, with limited enforcement and an unknowing public, shark fishing continues largely unabated in Honduras to date. To create the necessary baseline to identify changes in populations and inform the public about the large animals that ply their seas, we conducted the first large-scale marine megafauna monitoring project in the Caribbean of Honduras. The surveys monitor large animals (megafauna), including sharks and rays, and also sea turtles and big finfish (barracudas, snapper and groupers). Our methods are standardized, which allows us to compare results among countries and sites. We usually use three methods: Baited Remote Underwater Videos (BRUVs), in-water snorkel transects and scientific longlines. This year we were able to complete broad training in capture and release techniques with traditional fishers from several communities, and for the first time sharks were caught and tagged in Honduras!

A snorkeler adjusts a BRUV as it descends to the seafloor to record fish/shark abundance. Photo: Rachel Graham/MarAlliance


Since many sharks are very long lived (think of the Greenland shark that reaches over 400 years old!) and like us humans take many years to reach sexual maturity,  it will take several years of monitoring to determine if there are any changes occurring in the populations of these large animals. However, we can compare our results with other surveys throughout the region to get an idea of the health of Honduras’s marine megafauna. We are also already seeing some common trends, especially in Roatan. Greater abundance and diversity of finfish exist within protected areas with enforcement and more sightings of sharks in areas with less human activity – areas that actually do not necessarily coincide with protected area boundaries. This is not surprising, as studies have shown that sharks are most abundant in remote and little fished areas.

A rarely encountered small juvenile tiger shark (Galeocerdo cuvier) was the first captured and tagged shark in Honduras. Photo: Patric Lengacher/MarAlliance.


Although we did not catch as many sharks as we would have wished for on our scientific longline, our star capture was a juvenile tiger shark (Galeocerdo cuvier). This was an unexpected surprise, especially for our partner fishers, many of whom had never seen, let alone handled a tiger shark, a species often feared for its reputation as a voracious predator. Seeing the fishers’ enthusiasm and excitement for the capture and subsequently the release of an often feared animal gives us great hope that perceptions and behaviours can change in the shark’s favour. We can’t wait to expand this training and work to more communities and link the monitoring into our already popular Kids Meet Sharks program in Honduras.

The Deep: A new frontier for shark science


Standing on the veranda of our Belize based office, we can readily see the Belize Barrier Reef with its jagged coral reef crest, and beyond this line of coral and waves, the open sea. What many people don’t realize is that the reef shelf drops rapidly from a shallow 15 meters to over 1,000 m depth within a stone’s throw of the reef, and this is literally mare incognita (or unknown seas).

This proximity to deep waters and ease of access becomes highly relevant to fisheries management as near-shore coastal fish and fisheries are declining globally, and fishers are increasingly moving into the deeper waters in a bid to maintain their catch and meet the rising demand for seafood. Yet the deep sea environment is very little known throughout the world, and especially in the western Caribbean. Despite our lack of knowledge of this ecosystem, fisheries continue to develop in the deep sea. In the MesoAmerican Reef Region (MAR), almost nothing is known about the species that inhabit the waters deeper than 150 m (500 feet). In fact, we don’t even have a full catalogue of the deep-sea shark species that are in the MAR. To counter this paucity of data, MarAlliance is currently conducting research on the species that inhabit the deeper waters of the MAR to determine which species inhabit this region and which might be vulnerable to overexploitation from fishing.

Deep-sea sharks are remarkably well adapted to their environments, with many possessing large eyes, specialized teeth, and spiracles for pumping water over their gills in low oxygen environments. Upon capture, these sharks undergo a bit of a shock, moving from up to 500 m (1,200 ft) to the surface in under five minutes: not only are they exposed to extreme light conditions, but undergo a change in temperature from as little as 11°C (52°F) to 29°C (84°F).

We knew from other researchers’ studies that many deep sea sharks have extremely fatty livers and are therefore more buoyant than their coastal counterparts. Because of this, some species may have a difficult time swimming back down to depth after they are brought to the surface. We found that while smoothhound and night sharks swim rapidly back to the deep quickly after release, the bigeye sixgill sharks make a more meandering descent. Gulper sharks appear to have the hardest time, being both extremely buoyant and rather sluggish.

So we aim to get them back into the deep as quickly as possible.  Using a method commonly applied to finfish that we discovered also works well with sharks: a lead weight with a barbless hook attached to a line takes the shark down to depth very quickly. After a few trials, we feel like we have nearly perfected our technique, which we were able to use to successfully release a gulper shark on our last sampling trip.

As we have expanded our deep-sea shark research project in the MesoAmerican region, while working with the handful of traditional deep sea fishers to teach them monitoring techniques, we have also added to the number of species we are encountering. We now have a catalogue of seven species, a list that we are adding to with every major expedition we make. The deep is a new frontier that is both threatened by expanding fisheries, but also represents a region of new discoveries that keep us on our scientific toes.

Emerging Wildlife Conservation Leader


Building skill sets and knowledge and then applying them is what moving conservation forward is all about. Gabriela Ochoa, affectionately known by all as Gaby, is an enthusiastic conservationist focusing on sharks, rays and turtles and our National Coordinator for Honduras who has been keen to build her professional skills.

After much finger-gnawing, she received the great news that was awarded a place to pursue a masters at the University of Exeter’s top rated Center for Ecology and Conservation and simultaneously received a spot in the prestigious Emerging Wildlife Conservation Leader program. Spanning two years, this international program builds the capacities of young conservationists that have been identified as future leaders in their field.

Taking part in EWCL would not have been possible without the generous support of the World Wildlife Fund.
We look forward to Gaby applying the many lessons learnt to our program in Honduras as the programs unfold.

Networking fishers across ocean basins 


When Evan Cuevas grew up in the small un-electrified village of Monkey River in southern Belize, he never dreamt that he would become a trainer in good fishing practices. But that is exactly the journey this young lobster fisher embarked on earlier this year when he travelled half way around the world to the island of Pohnpei in the Federated States of Micronesia. Although Evan had been working with MarAlliance as a monitoring research assistant, his freediving prowess and canny lobster-seeking acumen came to the attention of Dr. Kevin Rhodes, MarAlliance’s Small Scale Fisheries Coordinator. Dr. Rhodes was seeking just the right person to train Pohnpei’s local fishers in methods to improve the sustainability of the country’s lobster fishery. Although we promote fisher exchanges between several countries where we work, this was an unprecedented exchange due to the distance traveled (more than 12,000 km!) and because the exchange focused on lobster and not sharks. We have learnt over the course of years that the conservation of large wildlife is often more successful when local needs and priorities are addressed first, and linkages between the health of wildlife and other species stocks are defined.

After a discombobulating trip across several countries and even more time zones, Evan met with the leaders in the fishing communities in Pohnpei and presented the story of lobster fishing in Belize. Evan was surprised to  find many similarities  between Belize and Pohnpei, as both countries have experienced declines in lobster stocks due to overfishing driven by rising demand. To protect the country’s most valuable fishery, Belize established a closed season and size limits and is now promoting the capture of live lobster through the use of the simple loopstick to reduce the capture of gravid females and undersize animals. Land based training with 40 of Pohnpei’s top traditional fishers focused on the making and use of loopsticks then rapidly transitioned to the sea. The fishers introduced Evan to stunning Pacific corals and reef fish that outshine their Caribbean cousins, while he showed them how to fish effectively with the new and more sustainable gear type. The exchange demonstrated that traditional fishers targeting the same resources don’t have to reinvent the wheel and a path to greater sustainability in the fisheries can be achieved through fostering peer to peer exchanges, in turn creating a vibrant network of traditional fishers across regions. We hope to support exchanges between fishers from Cabo Verde and the MesoAmerican Reef next as the west African fishers seek to organize themselves and become involved in the management of their fisheries.

We want to thank the fishers of Pohnpei for organizing the training, and Dr. Melissa Giressi who hosted Evan in Hawaii during his trans-Pacific journey.