Tenerife sits in the eastern Atlantic like a crossroads. Positioned roughly 300 kilometres off the northwest coast of Africa, the island intersects the paths of the Canary Current, warm subtropical surface waters, and the deep cold upwellings of the Atlantic basin. The result is one of the most ecologically productive marine environments in the northern hemisphere, a place where bluefin tuna from the Mediterranean share waters with tropical reef species and migratory whales from the polar ocean. What lives in these waters, and how those populations are changing, tells us something important about the health of the broader Atlantic system.

The Anatomy of an Exceptional Marine Environment

The waters around Tenerife support approximately 400 species of fish, a number that reflects the unusual convergence of marine provinces that the island straddles. [1] Its seafloor topography is dramatic: the island drops away steeply from the coast, reaching oceanic depths within just a few kilometres of shore. This proximity of shallow coastal habitat to very deep water creates conditions that support both reef-associated species and the large pelagic predators of the open ocean, sometimes within sight of the same beach.

In the deeper offshore waters, the Canary Islands are internationally recognised as one of the finest big game fishing destinations in the world, and for good reason. Atlantic bluefin tuna (Thunnus thynnus) pass through in their thousands between December and April, migrating northward toward Mediterranean spawning grounds. These are not small fish. Individuals regularly exceed 250 kilograms, and the largest bluefin recorded in these waters approach 450 kilograms. [2] Their spring passage coincides with dense schools of Atlantic mackerel (Scomber scombrus) and smaller baitfish that concentrate near the island, drawing the giants in from the open Atlantic.

Blue marlin (Makaira nigricans) and white marlin (Kajikia albida) are present from spring through autumn, the two billfish species that define Tenerife’s reputation among dedicated sport anglers. Spearfish (Tetrapturus belone) inhabit the deeper offshore trenches. Yellowfin tuna (Thunnus albacares), bigeye tuna (Thunnus obesus), wahoo (Acanthocybium solandri), and mahi-mahi (Coryphaena hippurus) complete a pelagic assemblage that few locations outside the tropics can match. [2]

Closer to shore, the volcanic reef structures support a different community. Atlantic amberjack (Seriola dumerili), barracuda (Sphyraena viridensis), grouper (Epinephelus spp.), and European sea bass (Dicentrarchus labrax) inhabit the rocky substrates, alongside numerous wrasse species, bream, and moray eels. The deeper sandy bottoms, where slow-jigging techniques are most effective, hold species less visible to tourists but central to local gastronomy: red porgy (Pagrus pagrus), sargo (Diplodus sargus), and various sparids that have been fished by Canarian communities for centuries. [3]

Reading the Signals: What Is Changing

The richness of this marine environment is not static, and the signals coming from the water are mixed. On one hand, the resident cetacean populations tell a story of relative stability. Whale Watch Tenerife, which has logged cetacean sightings systematically since 2018, recorded 17 different species in both 2018 and 2023, with short-finned pilot whales (Globicephala macrorhynchus) and bottlenose dolphins (Tursiops truncatus) present on nearly every survey day. [4] In 2025, orca sightings and encounters with fin whales were notable additions to the year’s record. [4] The continued presence of these apex predators is generally a positive indicator of ecosystem function.

On the other hand, the EU-funded OCEAN CITIZEN restoration project documented concerning trends at the base of the food web when it began its work on the island in 2024. Fish populations associated with rocky reef habitats have declined significantly compared to historical baselines. Seagrass meadows (Cymodocea nodosa), which serve as nurseries for juvenile fish and feeding grounds for sea turtles, have retreated across multiple coastal areas due to sedimentation, pollution, and rising water temperatures. Rocky reefs have been degraded by a combination of physical disturbance and the effects of ocean acidification. [5] These are not peripheral problems. Reef habitats and seagrass meadows are foundational to the productivity that ultimately supports the entire marine food web, from the smallest reef fish to the bluefin tuna and the pilot whales that hunt above them.

The Atlantic regulatory framework governing commercial fishing has also evolved. EU fisheries ministers, meeting in December 2025, set 2026 catch limits with 81 percent of total allowable catches in the northeast Atlantic at maximum sustainable yield levels — an improvement on previous years, though the failure to agree a mackerel quota for 2026 due to disputes with non-EU countries was a notable setback. [6] For sport and recreational fishing around Tenerife, a growing culture of catch and release has taken hold among charter operators, particularly for bluefin tuna, billfish, and other large pelagic species. Most reputable charters now apply mandatory release for bluefin tuna, reflecting both changing regulation and a shift in the values of visiting anglers. [3]

What the Fish Are Actually Telling Us

Marine ecosystems are exceptionally good at communicating ecological stress, if we know how to listen. The presence of 28 cetacean species, including year-round resident pilot whales, tells us that the deep-water food web west of Tenerife remains productive. The decline of reef fish populations and seagrass cover tells us that the shallower coastal zone is under sustained pressure from human activity. The continued migration of bluefin tuna past the island tells us that large-scale Atlantic management is beginning to take effect after decades of overfishing. The appearance of orcas and large baleen whales in 2025 tells us that the waters retain the biological richness to attract ocean wanderers from across the hemisphere.

Tenerife’s marine environment is neither pristine nor beyond recovery. It occupies a contested middle ground where genuinely exceptional natural heritage coexists with the pressures of one of Europe’s busiest tourist destinations. Paying attention to what lives here, in all its scientific specificity, is the first step toward deciding what kind of relationship the island will have with its sea.

Sources

1. Wikipedia: Tenerife — fauna and marine ecology
2. FishingBooker: Tenerife Fishing — The Complete Guide for 2026, fishingbooker.com, January 2026
3. FishingBooker: Canary Islands Fishing — The Complete Guide for 2026, fishingbooker.com
4. Whale Watch Tenerife: Tenerife Whale Watching Season — cetacean sighting data 2023-2025, whalewatchtenerife.org
5. OceanCitizen EU: Reclaiming Tenerife’s Ocean, oceancitizen.eu, September 2024
6. European Commission Oceans and Fisheries: Fisheries ministers agree fishing opportunities for 2026, December 2025, oceans-and-fisheries.ec.europa.eu

The shipping industry has spent years debating how to cut emissions without overhauling entire fleets or waiting for next-generation fuels that remain decades from commercial viability. A white paper released March 2, 2026, by the Institute of Marine Engineering, Science and Technology (IMarEST) in collaboration with Montreal-based AI company Whale Seeker and True North Marine suggests the answer may already be hiding inside every vessel’s bridge controls: the throttle.

The paper, titled Navigating with Nature: How Smarter Ship Routing Delivers Emissions Cuts and Biodiversity Gains, models a transatlantic route from Montréal, Canada, to Le Havre, France, and integrates ecological sensitivity layers, habitat vulnerability indices, and speed optimization algorithms into the voyage planning process. The results, based on a single route simulation, are striking: modest speed adjustments along the transit could avoid approximately 198 tonnes of CO₂, cut underwater radiated noise exposure by more than 50%, and reduce the risk of a fatal whale strike by up to 86%. The optimized route also yielded fuel savings of 61.7 metric tonnes per crossing.

Those numbers deserve context. A single transatlantic voyage producing nearly 200 fewer tonnes of carbon dioxide is not a rounding error. Multiplied across the thousands of commercial transits that cross the North Atlantic each year, the cumulative reduction potential is enormous, and it requires no new vessel construction, no experimental fuels, and no regulatory overhaul. It requires information and willingness.

The white paper builds on a growing body of research showing that the relationship between vessel speed and whale mortality is not linear; it is exponential. Studies published in Scientific Reports and cited by NOAA Fisheries have consistently demonstrated that the probability of a fatal collision increases dramatically above 10 knots. For the critically endangered North Atlantic right whale, which numbers roughly 380 individuals and is the subject of an ongoing Unusual Mortality Event declared in 2017, vessel strikes remain one of the two leading causes of death alongside fishing gear entanglement. NOAA data shows that 42 right whales have died and 40 have been seriously injured since 2017, with the vast majority of those casualties traced to human interaction.

What the IMarEST paper adds to this picture is an economic case. The conventional framing positions whale protection and commercial efficiency as competing interests: slow your ship to save whales, and you lose time and money. The Navigating with Nature model flips that assumption. By integrating real-time ecological data into route planning, the optimized voyage actually saves fuel. The speed adjustments are not uniform reductions across the entire crossing; they are strategic, applied in areas of high ecological sensitivity where whale density, calving grounds, or migratory corridors overlap with the shipping lane. In lower-risk stretches, the vessel can maintain or even increase speed to compensate, keeping overall transit time within commercially acceptable margins.

“What this case study shows is that smarter speed choices could cut costs and emissions now, while also reducing underwater noise and pressure on ocean biodiversity,” said Emily Charry Tissier, CEO and co-founder of Whale Seeker. Charry Tissier, a biologist with two decades of experience in coastal and Arctic ecosystems, founded the company in 2018 to use AI and aerial detection for marine mammal monitoring. Whale Seeker’s technology has since been deployed with Transport Canada to detect right whales in real time in the St. Lawrence corridor.

The underwater noise dimension is worth pausing on. Chronic noise pollution from shipping is one of the least visible but most pervasive threats to marine mammals. Whales and dolphins rely on sound for communication, navigation, and foraging. Elevated background noise from vessel traffic can mask their vocalizations, disrupt feeding behavior, increase stress hormone levels, and in extreme cases cause physical injury. The International Maritime Organization has recognized underwater noise as a significant environmental concern, but regulatory action remains voluntary and unevenly implemented. A 50% reduction in noise exposure through route and speed optimization, as the white paper models, would represent a meaningful improvement for cetacean populations along one of the world’s busiest shipping corridors.

Alasdair Wishart, IMarEST’s technical and policy director, framed the paper in regulatory terms. “This white paper illustrates how the landscape could look for vessel owners and operators should there be further legislation to protect marine mammals,” he said. The subtext is clear: the shipping industry can either adopt these practices voluntarily and capture the fuel savings, or wait for governments to mandate them and lose the first-mover advantage.

The paper was endorsed by the United Nations Decade of Ocean Science for Sustainable Development and produced through IMarEST’s Marine Mammal Special Interest Group, a technical body composed of experts from academia, industry, policy, and government. Strategic framing was supported by Fürstenberg Maritime Advisory.

It is worth noting what the paper does not claim. This is a case study based on a single simulated route, not a fleet-wide operational trial. Real-world implementation would face challenges including schedule pressures, port congestion, contractual obligations, and variable weather. The authors position the work as a starting point for integrating biodiversity intelligence into routing decisions, not a finished policy prescription.

Still, the fundamental insight is hard to argue with. In an industry under intense pressure to decarbonize, the notion that protecting marine life and reducing fuel costs can be pursued simultaneously, rather than traded against each other, is a compelling proposition. The ocean’s largest animals and the industry’s bottom line, it turns out, may have more aligned interests than decades of regulatory debate have assumed.

Source: IMarEST, Whale Seeker, True North Marine | Published March 2, 2026
White paper: Navigating with Nature: How Smarter Ship Routing Delivers Emissions Cuts and Biodiversity Gains | Available at imarest.org

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About the organization

The fishers of southern Tunisia called it “Daesh.”

The nickname, borrowed from the Arabic acronym for ISIS, was not chosen lightly. When the blue swimming crab first appeared in commercially significant numbers in the Gulf of Gabès around 2014, it behaved like an occupying force. The crustacean shredded traditional trammel nets with its powerful claws, devoured fish already caught in the mesh, and offered nothing in return. Coastal communities that had fished these shallow waters for generations watched their livelihoods unravel, one torn net at a time.

A decade later, that same crab has become one of Tunisia’s most valuable seafood exports. The transformation represents one of the most compelling case studies in adaptive marine resource management anywhere in the world: a nation that could not defeat an invader chose instead to monetize it.

The Mechanics of Invasion

The blue swimming crab, Portunus segnis, is native to the Red Sea and the western Indian Ocean. Its journey into the Mediterranean follows a phenomenon scientists call Lessepsian migration, named after Ferdinand de Lesseps, the French diplomat who oversaw construction of the Suez Canal. Since the canal’s completion in 1869, hundreds of marine species have drifted from the warmer Red Sea into Mediterranean waters. Most arrived quietly, filling ecological niches without disrupting local fisheries. P. segnis was different.

The Gulf of Gabès provided ideal conditions for explosive population growth. This vast, shallow continental shelf stretching along Tunisia’s southeastern coast had long supported the country’s most productive artisanal fisheries. Its warm, nutrient-rich waters now increasingly mimic the thermal regime of the crab’s native habitat as climate change pushes Mediterranean temperatures higher each year. Workshop outcomes from the 2025 “Blue Crab Management in the Mediterranean” conference confirmed what fishers already knew: the species has established a permanent, breeding population that now dominates the benthic ecosystem.

The ecological disruption extended beyond damaged fishing gear. The crab’s aggressive predation placed intense pressure on native biodiversity, particularly the autochthonous clam Tapes decussatus. This species forms the economic

The Policy Pivot

Eradication was never realistic. Once an invasive species establishes breeding populations across hundreds of kilometers of coastline, removal becomes biologically impossible without interventions that would devastate everything else in the ecosystem. Tunisian authorities, working alongside the Food and Agriculture Organization and the General Fisheries Commission for the Mediterranean, settled on a different strategy: commodification.

The approach required solving a practical problem first. Traditional trammel nets could not withstand the crab’s claws, but purpose-built crab pots could. These traps, constructed from durable materials and designed with selective entry points to minimize bycatch, allowed fishers to target crabs directly rather than losing their catch to incidental encounters. Government subsidies helped offset the cost of new gear, accelerating adoption across fishing communities.

The results exceeded projections. By 2021, Tunisia was exporting over 7,500 tons of blue crab annually, a figure that continued climbing through 2024 and 2025. Processing infrastructure expanded rapidly in southern cities like Zarzis and Sfax to meet demand from Asian markets, where blue crab commands premium prices. South Korea, Thailand, and Vietnam emerged as primary importers, joined increasingly by European buyers in Italy and Spain, along with growing interest from the United States.

Ripple Effects Across the Coast

The economic transformation reshaped coastal communities in ways that extend far beyond fishing boats.

For many fishers, blue crab provided income stability during a period when traditional target species like grouper and bream were declining due to overfishing and environmental degradation. The crab fishery operates on different rhythms than conventional fishing; traps can be set and checked on predictable schedules, reducing the uncertainty that has always characterized artisanal fishing.

Processing plants created thousands of jobs in communities where employment options had been limited. The work of picking crab meat from shells is labor-intensive and requires manual dexterity; machines cannot replicate the delicate extraction without destroying the product’s market value. Women from coastal communities filled these positions in large numbers, bringing household incomes into families that had previously depended entirely on what husbands and sons could catch at sea.

The “Blue Gold” rush also diversified Tunisia’s position in global seafood supply chains. The country’s fishing sector had historically depended heavily on fresh fish exports to the European Union. Blue crab opened new trade relationships with Asian buyers, reducing vulnerability to fluctuations in any single market.

The Shadow of Illegal Trawling

The crab story carries a darker subplot involving destructive fishing practices.

“Kiss” trawling, known locally as kys, is a form of mini-bottom trawling practiced in shallow coastal waters. The method drags weighted nets across the seabed, scouring everything in their path. It destroys Posidonia oceanica seagrass meadows, which serve as critical nurseries for marine life and significant carbon sinks. The practice is illegal precisely because of this environmental devastation, yet enforcement has proven difficult.

The explosion of blue crab populations initially drove more fishers toward illegal trawling. When crabs destroyed traditional nets, desperate fishers turned to gear robust enough to withstand the damage. Trawling equipment survives crab encounters better than trammel nets, even as it devastates the seabed. By 2022, an estimated 576 illegal trawlers were operating in the Gulf of Gabès.

The legalization and promotion of crab pot fishing offers a potential solution. By making legal trapping economically attractive, authorities aim to pull fishers away from destructive practices. Early reports suggest the strategy is gaining traction, though the immediate profitability of illegal trawling remains a significant barrier. Tunisia’s National Action Plan for Pollution Control explicitly links promotion of sustainable crab fishing to eradication of benthic trawling, treating the two issues as inseparable components of marine ecosystem recovery.

The Chitosan Frontier

Industrial processing of blue crab generates enormous quantities of solid waste. Shells constitute roughly fifty to sixty percent of each animal’s weight, and in the early years of the expanded fishery, this waste created new environmental problems. Discarded shells dumped back into the sea or piled in landfills produced odor and sanitation issues that strained relationships between processing facilities and surrounding communities.

Tunisia’s emerging blue biotechnology sector saw opportunity where others saw refuse.

Crab shells are rich in chitin, a biopolymer that can be converted into chitosan through chemical processing. Chitosan has high value across multiple industries: medical applications including wound dressings and drug delivery systems, agricultural uses as a natural pesticide and plant growth enhancer, and industrial applications in water treatment and bioplastics. The compound’s versatility makes it valuable enough that processed chitosan commands higher prices per kilogram than the crab meat itself.

Tunisian research institutes like the National Institute of Marine Sciences and Technologies have partnered with private ventures to develop industrial-scale chitin extraction. The country is positioning itself as a regional leader in what might be called third-order value creation: first the fishery revenue from meat exports, then the ecosystem service of removing an invasive predator, and finally the biotechnology input from shells that would otherwise become pollution.

The WestMED Initiative has cited Tunisia’s crab waste valorization as a best practice model for circular economy development across the entire Mediterranean basin. What began as a disposal problem has become a competitive advantage.

Lessons from the Laboratory

Tunisia’s blue crab story offers insights that extend well beyond this particular species or this particular coastline.

Climate change is accelerating species movements worldwide. Warming waters push marine life toward poles and into new habitats; the Suez Canal and other human-made corridors provide additional pathways for colonization. The Mediterranean, positioned between tropical and temperate zones and connected to warmer seas, will continue receiving new arrivals. How nations respond to these biological disruptions will shape coastal economies for decades.

The Tunisian model suggests that adaptation, rather than resistance, may offer the most practical path forward when eradication proves impossible. This requires institutional flexibility: regulatory frameworks that can pivot quickly, subsidy programs that can redirect fisher behavior, and research capacity that can identify commercial potential in unwanted species. It also requires honest assessment of what is achievable. The crabs are not leaving. The question becomes what to do with them.

For the fishers who once cursed “Daesh” while mending shredded nets, the answer has become surprisingly lucrative. The invader remains an invader, still altering the ecosystem in ways scientists are working to understand. But it is also now a livelihood, an export commodity, and a raw material for industries that did not exist in Tunisia a decade ago.

The transformation did not happen by accident. It required policy intervention, international cooperation, investment in processing infrastructure, and willingness among fishing communities to adopt new methods. Not every invasive species will offer similar opportunities; many will simply cause damage without redemption. But where commercial potential exists, the Tunisian experience demonstrates that crisis can become catalyst.

Blue gold, it turns out, was hiding in the claws of disaster all along.

Written by: Junior Thanong Aiamkhophueng

Attribution: This article draws on reporting from FAO and the General Fisheries Commission for the Mediterranean on blue crab fisheries management; El País coverage of the economic transformation; SPA/RAC technical workshop documentation; IW:LEARN and ARIJ reporting on community impacts; and WestMED Initiative blue economy research. Charfia photo via Wikimedia Commons; Portunus segnis photo via Wikimedia Commons CC0; fishing and crab trap photos ©FAO/Valerio Crespi. For further reading, visit The Guardian, Green Prophet, and Environmental Justice Foundation.