MarAlliance

Traditional Pohnapeian free-diver and fisher Taylor Paul brings up a Epinephelus fuscoguttatus as part of spawning and spatial ecology research conducted on the species. Photo: Rachel Graham

Small scale fisheries represent a chain with a variable number of links that includes the fish, the fisher and the buyer, often with additional links such as markets, resellers, wholesalers, stores or restaurants and the final consumers. Each link sets up demand that can undermine the sustainability of vulnerable coral reef-associated fisheries. In small communities, a key link in the value chain that drives the demand for fish and provides a centralised location for fishers to sell their fish is the fish market. Often created and run by non-fishers, markets create demand that often supersede the ability of fisheries to yield fish without significant long-term impacts to the fished populations.

A diversity of reef-associated fish species are brought in for sale at road side stalls in Pohnpei. Photo: Rachel Graham

To address this issue in Pohnpei, a coral rimmed island in the Western Pacific’s Federated States of Micronesia, Dr. Kevin Rhodes, MarAlliance’s Coastal Fisheries Coordinator, has been working closely with fishers, market owners and fishing communities to return the coral reef fishery to sustainable levels. An earlier market study in 2006 had already found the fishery to be overharvested, with a reliance on unsustainable nighttime spearfishing, juveniles and spawning aggregations. By 2015, marketed volumes were down nearly 20%, along with catch-per-unit-effort and income. This year, Rhodes is working with Pohnpei’s fisher association, Menin Katengesed, to turn this situation around by helping them open their own market, set their own pricing, and set standards and restrictions around purchases to help eliminate nighttime spearfishing and build much needed coastal fishery economies.

Dr. Kevin Rhodes reveals a cooler full of recently captured grouper in Pohnpei. Photo: Rachel Graham

The project, funded jointly by NOAA Saltensall-Kennedy, the Canada Fund for Local Initiatives, Global GreenGrants and the Packard Foundation through the Micronesia Conservation Trust, is working to empower fishers to take control of fisheries management through economic means, while providing the association with a self-financing tool to continue community outreach, support market operations and build on opportunities to reduce overhead and improve profitability of fishing. Currently, the market is supplying at-cost ice and long-storage coolers to fishers as a rent-to-own option that can be purchased in return for supplying sustainable catch. The association also looks to value-add to marketed fish by diversifying products, such as making tuna jerky and smoked fish and using waste to make fish emulsion for local farmers.

The market will also provide an opportunity for MarAlliance’s team to collect fisheries data and examine the life histories of several target species for which nothing is currently known. Once the data is collected and analysed, Rhodes will help the state and the association develop management regulations around identified spawning times and life history parameters. These key data are useful to establish temporal catch bans around reproductive periods and catch size limits, both of which help to eliminate the catch and sale of undersized fish.

If successful, the operation can serve as a blueprint for other area markets and beyond Micronesia’s extensive territories. With these locally-based initiatives, Rhodes can help to steer Pohnpei fisheries back to sustainable levels with fishers at the wheel.

A night shark immobilized in water by the research boat and awaits measurement, tagging and release. Photo: Simon Gulak

Monitoring large, mobile and little known species requires a lot of work and dedication, and not a small amount of luck. We’ve all had days, and even weeks where we just can’t catch a break (or a shark), despite all factors – good weather, ideal location, great crew – being in our favor. And then there are the days that get us through the rough patches, where everything clicks and we get amazing results.

This past July we had a bit of both types of luck during the deep sea project: two long, hot days during which we caught absolutely nothing, followed by one single day in which we tagged and released nine sharks from three different species. The first two sharks we caught that morning were, ironically, night sharks (Carcharhinus signatus), which although considered primarily deep-dwelling (50-600 m), don’t have a lot of the characteristics we associate with deep-sea sharks, such as huge eyes, water-pumping spiracles on their heads, or light-emitting organs. Rather, they look quite similar to other “sharky sharks,” like the silky shark or even Caribbean reef sharks. In fact, they’re closely related to their shallower cousins, being in the same genus.

The night shark soon to sport tag 411 that would travel from Belize to Cuba over the course of two months. Photo: Thomas Meyer

Until last year, we only had anecdotal evidence that night sharks even occurred in Belize, and most people thought they were brief seasonal visitors to one atoll in the south of the country. But as we learn more about this species we are finding that they likely occur throughout the country, and may be here year-round. We’ve now tagged and released eight night sharks, and have recorded a ninth on one of our deep Baited Remote Underwater Videos (BRUVs). It’s not a huge sample size, but it’s providing some important data for this understudied species.

Tagging highly migratory sharks with conventional tags – those that do not communicate with satellites or receivers – is largely an exercise in futility. After all, many species of sharks can cross ocean basins in just a few weeks, and often tags are not reported by fishers, as many assume they will get in trouble if it is a protected or special species. So we were more than a little surprised to get a message earlier in October that one of our conventional tags had been recovered in Cuba. A quick search for the tag number in our database revealed that it was one of the night sharks we had tagged just two months earlier!

Although we are thrilled to have this information, this exciting finding is tempered by the implications of its capture. While it was reportedly released, this shows that at least 12% of the night sharks we tagged have interacted with fishing gear. Given what we know about low reporting rates, the number of night sharks being captured in the region is likely very high. Night sharks are listed as Vulnerable to Extinction by the IUCN Red List of Species (redlist.org), which is an organization that uses scientific and fishery information to evaluate the global status of species around the world. Once common in Caribbean fisheries, and especially Cuba, night sharks are now considered rare throughout the western Atlantic Ocean and the Caribbean. Their Vulnerable status is a result of heavy and unregulated fishing of the species, especially around seamounts off Brazil.

These first records of night sharks in Belize show that this species likely traverses our waters throughout the year, and may even use Glover’s Reef as a mating aggregation. As most Belizean fishers do not target deep water sharks, they are fairly well protected while they are here, but increasing fishing in deep and pelagic waters, and especially in surrounding countries, will continue to threaten this highly migratory species. We don’t know where our night shark went after its presumed release in Cuba- was it to US waters where the species is fully protected, or did it loop to the south where it would encounter heavy fishing activity? How large is its range and how many fisheries is it exposed to as it migrates? These are just some of the questions about this and other vulnerable species we are starting to answer with this project.

Learning to use a Global Positioning Service device and accurately recording field data are some of the many skills that students receive during the Mnine d’Mar course.

It’s dawn when Mohammed wakes up in the Barraca (Portuguese for slum) where he lives in the back of Sal Rei, the capital of Boavista, Cabo Verde. He can just catch sight of the ocean glinting in the morning light beyond the saltpan as he finds a quiet spot on the edge of the slum to do his necessities. Although the small desert island of Boavista is surrounded by the Atlantic Ocean, most of the people living in the Barraca, where Mohamed lives, rarely get the chance to swim and many only know the animals living there when they are served up on a plate.

The arid climate in Boavista means people are dependent on the surrounding ocean for food, and living costs are high, as nearly everything else has to be imported. Additionally, house prices are inflated by the surging tourism industry, meaning many families cannot afford to rent. As a result, although there are only 15,000 people on the island, barracas (slums, lit. ‘huts’) comprise nearly half the population.

For many of people living in the Barraca the choice is simple – either work in the hotels or become a fisher. As growing tourism, drives further population growth from continental Africa, the sea is inevitably coming under greater pressure. And sharks, which are still viewed by many as the monsters perpetuated by Hollywood, are some of the first species to disappear. There is empathy driven by misperception. The irony is, it’s these maligned predatory species, which maintain fish and even ecosystem health and, losing them is likely to impact the small-scale fisheries on which these people depend.

It is in this context that we began our Mnine d’ Mar educational project, to strengthen the connection between local children and the ocean with a focus on sharks and rays. The program has provided us with great opportunity to raise awareness and breakdown common misperceptions at an early age. In doing so we hope to build a generation that values sharks and rays for their role in the marine environment and who can benefit directly from their survival.

The program runs across three days, developing from a classroom environment, to experiential in-situ learning and ultimately culminating with practical sessions at sea. The first day sets the scene, using a combination of theoretical, interactive and practical learning; we encourage participation and try to steer towards group discussions, games and interactive activities.

The Mnine d’ Mar starts off in the classroom and transitions to the coast and then the sea.

On the second day, in the shadow of an acacia on the beach, we discuss perceptions, environmental issues and marine conservation putting it in a local context. On the third day, we take the kids to sea to conduct scientific monitoring in the bay next to the city, using UVS (underwater visual census) snorkeling and BRUVs (baited remote underwater videos). On the one hand, it is a chance for the kids to explore the marine realm with their own eyes, something many on the island rarely, if at all, get the chance to do. On the other, it allows them to get to ‘know’ their local species and establish a connection something essential if empathy is to be surpassed and conservation is to be successful.

Cintia Lima orients the students on the beach of Boavista during one of the Mnine d’Mar training exercises

The Menin’ de Mar Class of 2017 at the ready for the marine component of their course led by Cintia Lima (in blue)

Time to apply all the classroom based learning to the work on the sea monitoring fish for species diversity and abundance.

Mohammed grins while watching himself swim underwater along with family members as part of the follow through post marine training in the Mnine d’ Mar program

By providing knowledge and first hand experience we hope to captivate an interest in marine ecology and encourage thinking about conservation and sustainable management of marine resources, something extremely pertinent in Boavista, where the Sahara meets the sea. We envisage a future where big fish and sharks thrive and in which people like Mohammed benefit from their conservation, if not directly then at least from the knowledge that this wildlife exists and helps keep the oceans healthier. By raising awareness and cultivating skills for science at an early age we hope to build the foundation and a professional demand for marine science and conservation in Cabo Verde and create a generation connected to the sea that surrounds them and the sharks and rays that live there.

Kevin dos Santos (aka the future of sharks in Boavista) learning some cool shark and ray facts.

When we are asked the question “How old are you?” we can usually answer with a degree of accuracy. Things are somewhat more complicated for fish and very much more for sharks – and not just because they can’t literally tell us how old they are.

The ageing of fish is believed to originate from speculations made by the scientist Aristotle in 340 B.C. He noted, in the Historica Animalium, that fish age may be determined by examination of the size and hardness of fish scales. However, it was not until the invention of the lenses and the microscope in 1650s, that scientists were able to identify growths rings in the scales that were similar to those found in trees. By 1924, these rings, known as annuli, were found in otoliths (ear bones), vertebrae, fin rays, and other hard structures. It was also noted that there were variations in the amount of growth over the year with the majority of growth occurring during the summer months.

Sharks and their relatives, rays and chimeras, do not have a bony skeleton. Their skeleton is made of cartilage which is lighter and more flexible. Their otoliths, or staticonia, are similar in size to sand grains and their scales (known as dermal denticles) do not grow continuously. Some species have hard spines that contain rings suitable for ageing, but this is not the case for many elasmobranchs. Vertebrae are used to age the species without spines and this is only possible after the animal is dead.

A thin section of shark vertebrae under the microscope showing the banding pattern (NOAA Fisheries)

Today ageing fish and shark species is a vital part of fisheries management. Ages are important data that are used for assessing the health of a population of a species (also known as a stock). The age of maturity and growth rates may tell us how vulnerable a species is to being over harvested.

Before we can confidently use age estimates for a species, the rate of growth ring deposition must be validated. This is frequently achieved by injection of fluorescent dyes (e.g. oxytetracycline, calcein) into a tagged animal prior to release. The dye incorporates into the age structures so that when the animal is recaptured, the point in time when the animal was tagged will be visible. Thus the amount of growth deposited since the tagging event can be confirmed.

Another method of age validation uses the levels of the radio-isotope of carbon known as  C14 in the growth zones of the vertebrae to match it against references with known timelines such as  coral reef cores. This isotope is a direct result of nuclear testing during the 1950s and has hence earned the title “bomb carbon dating”. However, a recent review of both these methods has suggested that the underestimation of shark ages may be more widespread than previously thought. Growth bands on aged structures may actually only be reliable during the early years of life. This new evidence will be important to future ageing studies and the resultant impact to the life history and conservation status of sharks and rays.

Rock saw used to section otoliths and vertebrae

Thanks to the ongoing collaboration with Sea Leucas, a small start-up in the field of fish ageing, MarAlliance now has ready access to two age/production saws for taking sections of shark vertebrae and fish spines and otoliths. We have begun to process our collections and look forward to working with other researchers along the MesoAmerican Reef to age their animals.

Roxane Borruat taking length measurements of the fish landed at the port of Boca Parita, Azuero Peninsula, Panamá. Photo: EM Valderramos Piminchumo/MarAlliance

High fishing effort coupled with unsustainable use and destructive practices such as nets, has resulted in the loss of marine biodiversity and in the deterioration of marine ecosystem services since the middle of the 20^th century. One of the most important of these services is the provision of food, which implies that the loss of biodiversity and the decline of marine populations engendered by unsustainable fishing practices have the potential to also affect food security. Assessing the impact of net fisheries has been challenging in many countries due to a lack of control sites where more sustainable practice such as hook and line are used.

Panamanian artisanal fisheries, including those of the Azuero Peninsula, follow the same global trends and yet also suffer from a lack of information which hinders adequate management. The Government of Panama’s Department for sustainable fisheries (ARAP), recently urged the need for improved scientific knowledge on the country’s small-scale fisheries which tied in well with our expertise. We were also keen to work with fishers from two communities located on Panama’s Azuero Peninsula who use different fishing gears to assess catch size and composition and highlight any differences due to gear preference.

Major findings

Some of the most important species for the studied artisanal fisheries include slow growing and long-lived species, such as snappers and groupers. Such characteristics make these species especially vulnerable to fishing pressure. The majority of species that were landed at both ports were assessed by the IUCN as of least-concern in relation to risk of extinction, although it was unknown for most of them whether their population is increasing, stable, or actually decreasing.

Based on conservation status, economic value, and the amount of data collected, 8 focal species were chosen for further analysis. The landings of 7 out of these 8 species were biased towards smaller individuals. In some cases, the great majority of the specimens that were sampled were below the size of sexual maturity. Therefore, specimens may be commonly caught while still immature. Alternatively, these populations may have suffered from miniaturization due to fishing pressure, meaning that their specimens mature earlier (at smaller sizes) and their maximum size is smaller than normal, as a consequence of the selective removal by fishing activities of bigger fish from the population. The most worrisome result concerned landings of the endangered scalloped hammerhead shark (S. lewini), for which newborn specimens were prevalently landed. In other words, scalloped hammerhead sharks are commonly caught before they have reached sexual maturity and hence before they could reproduce. There is also a portion of the fishery specifically targeting adult scalloped hammerheads, of which the fins are worth more than the meat and are sold separately.

The landing site of the artisanal port of El Arenal, Azuero Peninsula. Photo: R. Borruat/MarAlliance

Juvenile blacktip sharks landed at the port of Boca Parita, Azuero Peninsula, Panamá. Photo: R. Borruat/MarAlliance

Tino the tiger shark delights the crowds in Boavista, Cabo Verde.
Photo: MarAlliance

Engaging students and the public about sharks and rays, and the need for greater understanding and conservation measures, has created an unexpected space and platform with schools and the public to talk about other urgent issues impacting the sea, notably plastic pollution. Like many island nations, Cabo Verde has a problem with waste disposal. Being a group of small windswept islands, a large amount of waste – especially plastics, inevitably enters the sea. This long-lasting rubbish impacts marine species and their habitats, and increasingly ends up back on our plates inside fish. It is estimated about 1/4 of caught fish have ingested plastics, though it is not yet known what effect this might have on us.

A recent study estimated that by 2050 there will be more plastic in the ocean than fish. While this is disturbing on many levels, it is especially concerning because plastic and other synthetic materials contain persistent pollutants, some of which can mimic and disrupt biological hormones and can take hundreds of year to decompose. During the time plastics are at sea, they are often mistakenly eaten, and can accumulate at potentially harmful levels in fish. And it’s not just bony fish who are feeling the effects, but seabirds, marine mammals and even sharks fall victim to ingestion and entanglement of our waste and discarded fishing gear.

Although plastic pollution is being increasingly studied, for many the problem remains out of sight and out of mind. Because we appreciate a challenge, in May we decided to integrate this new threat into our education and outreach program in Cabo Verde. We spent the month running an educational campaign on the impact of rubbish on marine fauna. By visiting schools, running interactive workshops with students, taking part in radio shows and holding outreach events, we are raising awareness to ensure that this broad threat to the marine environment remains highly visible and that we help to identify solutions to minimize waste and pollution.

Cintia Lima shares the pitfalls of plastic pollution in the sea. Photo: Zeddy Seymour/MarAlliance

Combating plastics pollution also has a powerful ally in our new team member, our friendly mascot, Tino the tiger shark. In the wild, tiger shark numbers have fallen significantly in the last 50 years as a result of overfishing. We also know that tiger sharks are fairly omnivorous and have been found with all sorts of plastic and metal rubbish in their stomachs. Tiger sharks are often stigmatized and viewed as a senseless monster. By promoting scientific fact instead of fiction and putting a great face to conservation, including plastic pollution, we are dismantling myths and changing perceptions at an early age, with the goal of cultivating pride for this iconic and critical species and encouraging strong connections to the sea.

People are remarkably fascinated by sharks. Whether they evoke fear, love, or pure curiosity, it is usually not very difficult to get people excited about sharks, especially kids. This has been clearly evident during our education and outreach events in Panama this year. Since the beginning of the year we’ve been able to engage the public with an educational booth at two large fairs, as well as talk to over 800 students and teachers from primary schools in Panama City. Besides teaching people about the incredible diversity of sharks and rays and sparking their curiosity about shark biology and anatomy, we also share the reality of unsustainable fisheries and what is happening to many of Panama’s sharks. And they are devastated.

To meet the demand for more highly-prized fishes whose populations have drastically decreased in the last few years, it is not difficult to now find shark meat sold in fish markets and even supermarkets across the country. Ambiguously labeled as ‘cazón’, ‘corvinata’, ‘tollo’, or simply ‘pescado’ (fish) instead of ‘tiburón’ (shark), most of the public in Panama have no idea that the fish they are eating is actually shark meat. Hammerhead sharks are being hit particularly hard, as gillnets are used to catch large quantities of juveniles at coastal nursery sites along Panama’s Pacific coast. At the height of the reproductive season, when hammerheads migrate to Panama to give birth, a single boat may catch hundreds of newly born sharks in a day.

Trunks of juvenile hammerhead sharks caught in artisanal gillnet fisheries on Panama’s Pacific coast. Photo by Megan Chevis.

But what we’ve learned from our interactions with kids and the public at large in the last few months in Panama is that, once they know about sharks and their plight, people generally don’t want to eat them. Few of them know that there are hundreds of different species of sharks and rays inhabiting a variety of marine habitats around the world. Or that not every shark is a ‘white shark’ that wants to eat humans. Even fewer know that the meat from sharks and other large marine predators contains high levels of toxic methyl-mercury, or that it can take a hammerhead 10-15 years to reach reproductive age. Through these interactions we hope to not only change people’s perceptions of sharks (and inspire the next generation of marine biologists, divers, and ocean lovers), but arm them with knowledge so that they can make more informed decisions about what they consume that will ultimately make long-term positive changes for sharks.

Students marvel at a shark’s jaw as they learn about shark evolution and diets. Photo: Megan Chevis/MarAlliance

The wonders of the small world or a new view through a microscope. Photo: Rachel Graham/MarAlliance

Sometimes it’s not just the big things that inspire awe, it’s the little things too. The really small, microscopic things. When we educate students about fish, notably sharks and rays, we tend to talk about the whole animals, their diet, behavior, form and function. And yet to demonstrate the phenomenal diversity of each species, we are turning to microscopes to reveal a new world that generally remains out of sight and mind for most.

We recently began to use microscopes to expand our education program and relate the fine structure of skin, muscle, teeth, and more to how sharks and rays have evolved, how they eat, move and combat predation, all of which has inspired students learn about the biology and building elements of each species. Our original kids’ style microscopes made such a huge impression on students and adults at the Belize Punta Gorda outreach event that we were convinced to expand the program further. We happened to be looking for funding to purchase more units and integrate them into all of our country based educational programs when the Houston Zoo stepped in and coincidentally said “Wait, we have just what you need! Would you like some microscopes?”

MarAlliance’s Rachel Graham is marvelling at the generous microscope donation by the Houston Zoo’s Director of Education, Melanie Sorensen.

Our wonderful donation of eight high quality microscopes to MarAlliance is now enabling us to expand our educational programs in Belize, Honduras, Panama and Cabo Verde. We can’t wait to amaze and inspire more generations with science and beauty of the minute.

Curious nurse sharks and southern stingrays dance with a snorkeler at Shark Ray Alley. Photo: Rachel Graham/MarAlliance

Tourism focused on encounters with sharks and rays has increased dramatically worldwide as people increasingly seek out the animals they once feared, and are keen to experience the thrill of meeting large marine wildlife up close. Successful wildlife tourism is predicated on predictability, and one way of increasing the possibility that visitors will encounter sharks and rays is by feeding the animals. This practice, also known as provisioning, has polarized biologists, who fear that feeding modifies natural behavior and also creates expectations where animals see people and expect food. There are studies that support all of these aspects, yet in countries where sharks and rays are killed, the positives of provisioning generally outweigh the negatives. Provisioning sites can help people to encounter animals that are otherwise feared and provides high non-consumptive value for sharks and rays through tourism.

The lack of information about many provisioned aggregations of sharks and rays worldwide extends to one of the longest-known provisioned sites: Shark and Ray Alley in Belize’s Hol Chan Marine Reserve.  With visitors to the marine reserve and its sharks and rays topping 75,000 people a year, the need to assess the size, demography, recruitment and diversity of species of the aggregation became the focus for our long term monitoring study. The methods are simple, consisting of weekly video and photo surveys of the individual nurse sharks (Ginglymostoma cirratum) and rays to determine whether feeding activity has affected the behaviors and habitat use of the animals at Shark Ray Alley.

Our research at Shark Ray Alley consists of individuals gathering size estimates and sexes of the sharks and rays. We also gather population counts and photo identification of the animals on site. To gather such information, we travel to Shark Ray Alley once a week with either a tour operator during their scheduled time if space is available, or with a Hol Chan Marine Reserve ranger. Upon arrival we make an initial count from the boat of the number of sharks, rays, and turtles  present. We also gather and record environmental conditions and a number of other factors including the number of guests, whether chum is used, type of chum used, and the number of other tour boats in the area. Most often we have two surveyors; one recording data and taking in water photos of individual dorsal fins, and the other using a size estimation tool with a GoPro attached recording underwater video of the animals. Here we continue the survey until the tour ends, or all of the animals vacate the area.

The most responsible tour operators use a chum tube stuffed with sardines and lowered to the seabed, to attract sharks and rays to their boat. Photo: Rachel Graham/MarAlliance

By gathering such information, we will be able to estimate average numbers of each species from the boat and in-water, average sizes, and proportions of males versus females, along with ecotourism data including average number of boats, how many tour boats feed/chum and how tour operators and tourists interact with the animals, and whether they are touching or handling the animals (which unfortunately several do).

Initial trials with a colleague’s drone highlights this as an efficient method of monitoring the provisioned aggregation from the sky. So our next step involves the purchase of a drone that will enable replicable aerial surveys to reveal abundance of animals and boats, animal behavior in relation to boats and will allow us to have a much more complete picture of the aggregation. We at MarAlliance have our very first GoFundMe campaign underway to make aerial monitoring a reality and a weekly occurrence with our surveyors. If you are keen to support our Eyes in the Sky project please visit our campaign at: https://funds.gofundme.com/dashboard/eyes-in-the-sky-to-monitor-sharks. Any size donation is most welcome.

It is clear that wherever shark and ray aggregations occur, either provisioned or natural, the sites are becoming tourism attractions. With good site management and shark and ray encounter etiquette applied by guides and rangers, such as no touching or chasing the animals, no hand feeding (use a feed tube or like), and briefing guests fully on the experience and protocol prior to entering the water, these predictable aggregations can transform a fear of sharks by many into appreciation, respect and stewardship for these magnificent creatures. And this is why we would much prefer a shark to be fed than dead.

A friendly Southern stingray checks out the photographer front as we take measurements to check on growth over time. Photos: Rachel Graham/MarAlliance

Two key boats for our research, Ze Luis Monteiro’s 6 m skiff “Stephanie” (Ze is in the light blue T-shirt) and the slightly larger Yersin belonging to Monaco Explorations (74m). Photo: Rachel Graham/MarAlliance

Our team of conservationist scientists and fishers loves boats. We love them. Big or small, but preferably trustworthy. They are a key vehicle to our objective of finding, studying and conserving fish. We usually work out of rather small boats 6-7 meters long outfitted with outboard engines that one can only work in during preferably good seas, so when the invitation to work with Monaco Explorations off of a large research vessel in generally unexplored waters popped into our inbox, we gasped with delight.

Fast forward several months and we are actually working off of said vessel, whose use for research during a three year circum-tropical exploration mission was recently inaugurated by the Prince Albert II of Monaco. Named after a famous doctor who identified the plague, Monaco Exploration’s motor yacht is named the Yersin; it measures 74 meters long, has three tenders, a back wet deck, wet and dry labs, lots of fabulous cold storage and a computer room. And everything is rounded off by beautifully outfitted cabins with chic moderne decor, splashes of art nouveau and ancient mariner trinkets. It has been a huge treat for our crew to be able to easily take a shower after hours at sea, be fed by the ship’s two super cooks and sleep in such comfy beds while in the “field”.

Lowering one of the Yersin’s tenders into the sea off the coast of Boa Vista, Cabo Verde

But we digress (so easy to do on this boat…did we mention we love big comfy boats?), we’re all here to explore and advance science and understanding of fish, and these are exactly some of objectives for working in Cabo Verde. With four scientific teams (MarAlliance, University of Montpellier, ZSL and SpyGen) and traditional Cabo Verdian fishers collaborating to better understand the diversity and abundance of marine megafauna (large fish, turtles and cetaceans), we are focusing on the capture and tagging of sharks and the in-water tagging of megaplanktivores (manta rays and whale sharks) to better understand their use of the island’s seas, notably in relation to the coastal and offshore industrial fishing fleet that overlap with many of the animals habitats.

Team leaders meeting with Expedition Chief Pierre Gilles and Yersin Captain Jean Dumarais. Photo: Rachel Graham/MarAlliance.

Our voyage of discovery has just begun but we’re off to a promising start with the tagging of two manta rays with satellite tags. We look forward to sharing more of the expedition details and keeping all of our team – and this includes you, our readers and supporters – apprised of our discoveries in upcoming posts and via our Facebook and Instagram feeds when at sea internet permits. Until then, happy motoring.

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.