Sharks

Range and fishery interactions

• Oceanic whitetip sharks are found in warm waters throughout the Pacific, mostly between 30°N and 30°S. They are highly migratory and typically inhabit the upper mixed-layer of the open ocean. This brings them into frequent contact with tuna fishing gear. They often follow scent trails to longline baited hooks set in the top few hundred meters, and they are known to aggregate around FADs (which makes them susceptible to purse-seine bycatch when tuna schools associate with those FADs). Historically, they were a common bycatch in tropical tuna fisheries, but populations have become so reduced that encounters are now relatively rare – a concerning sign in itself.
• Because oceanic whitetips often remain near the surface even in daytime, they were frequently captured by shallow-set longlines and by any intentionally deployed “shark lines.” Even in deeper sets targeting tuna, some whitetips get hooked during setting or hauling when gear is shallower. In purse seines, most interactions occur when juvenile whitetips associating with FADs get entangled in the net or are inadvertently brailed aboard with the tuna catch. These sharks have a high at-vessel mortality rate – they often fight hard when hooked, leading to exhaustion or injury.

Effective bycatch mitigation

• The most direct mitigation is the ban on targeted shark gear: by removing wire leaders and not allowing shark lines, longline fishers effectively decrease the catch of oceanic whitetips (and other sharks). Monofilament leaders give any hooked whitetip a chance to bite off and escape. Early data after these measures suggest fewer whitetips are being landed on compliant vessels, indicating the gear changes are working.
• For purse seiners, avoiding entanglement is key. The adoption of non-entangling FADs – FAD designs without hanging net webbing – prevents many sharks (including oceanic whitetips) from getting ensnared underneath FADs. Crews are also trained to look for sharks (and other species) when a FAD is encircled; if a whitetip is seen in the net, they should release it while it’s still in the water (e.g., using a release chute or lowering a section of the net) rather than hauling it aboard.
• When a whitetip is hooked on a longline, the crew should refrain from gaffing or lifting it onboard (which could injure the shark and crew). Instead, they should cut the line as close to the hook as safely possible, ideally leaving only a short length of leader attached to the shark. Using a long-handled cutter for this purpose keeps crew safe and increases the shark’s chance of survival. Some fleets have also trialed weak hooks (that straighten under big fish like sharks) as a mitigation measure, though this can risk losing target catch as well.

Monitoring and enforcement

• The rarity of oceanic whitetip sightings now means that high observer coverage or electronic monitoring is needed to detect any events and ensure compliance with the no-retention rule. WCPFC is moving toward higher monitoring coverage in longline fleets; 100% observer coverage is already in place for many purse seine vessels, which helps verify that whitetips, if caught, are indeed released and not finned. EM (electronic cameras) can be particularly useful on longliners to document shark handling practices on deck.
• Port inspections and transshipment monitoring are another enforcement tool: authorities check landed tuna catches for any hidden shark fins or carcasses. Because oceanic whitetip fins were historically valuable, there’s risk of illegal retention. Strong penalties (including potential blacklisting of vessels) and cooperation among member countries aim to deter any such violations. WCPFC compliance reports in recent years have noted improved adherence, but also stress continued vigilance.
• Scientists continue to monitor oceanic whitetip recovery (or lack thereof) through fisheries-independent surveys and modeling. They use catch-per-unit-effort (CPUE) trends from observer data as an index of abundance. So far, any signs of population increase are not clear, likely because even minimal ongoing mortality impedes growth of such a depleted stock. Continued protection and further bycatch mitigation innovation (e.g., exploring shark repellents or avoiding certain hot spots) remain priorities for this species.

Biology and interactions

• Silky sharks are a tropical and subtropical species, mostly found between 20°N–20°S in the Pacific, often in the upper 200 m of the water column. They have a tendency to aggregate around floating objects (both natural debris and man-made FADs) because these areas concentrate prey. This behavior unfortunately increases their encounter rates with purse-seine gear: when a FAD is encircled for tuna, groups of silky sharks that were underneath can be caught as bycatch. Purse-seine observer data historically showed silky sharks as the most common shark species caught in such sets, especially young sharks of 50–100 cm length. In longline fisheries, silkies (particularly sub-adults and adults) are caught on tuna hooks as bycatch, mostly in shallower sets in tropical waters. They are less hardy than some sharks; a significant fraction caught on longlines are found dead by the time the gear is retrieved.
• In terms of life cycle, silky sharks mature at around 6–10 years of age and can live 20+ years. Their moderate growth and reproduction mean populations can only tolerate low to moderate levels of fishing pressure. In the 1990s and early 2000s, a combination of targeted fishing (for fins) and high bycatch in tuna fisheries caused steep declines in silky shark numbers regionally. Scientists noted declines in standardized catch rates and mean sizes – signs of overexploitation. The species’ Vulnerable listing reflects these global declines, though some regional sub-populations (e.g., in the central Pacific) might be worse off than others.

Mitigation measures for fleets

• Purse seine fleets have been encouraged to adopt shark-friendly practices: avoid deploying FADs in areas during seasons of exceptionally high juvenile silky presence, and monitor FADs for shark activity (via sonar or cameras) so they can decide to skip a set if too many sharks are present. When silkies are caught in the net, crew should prioritize their release. Methods include using a dedicated “shark release net” or canvas sling to lift larger sharks out of the main net and over the side, or opening a portion of the net early. Some vessels have experimented with small meshes or escapement devices that let small sharks slip out during net hauling. Every shark released alive is a small victory for conservation, so crews are instructed on handling do’s and don’ts (e.g., do not gaff or stab sharks, minimize time out of water).
• Longline vessels, besides employing monofilament leaders, can reduce silky shark bycatch by avoiding setting shallow hooks at dusk/dawn in certain areas where silkies are common. Some fishermen report that using fish bait instead of squid might slightly reduce shark bite frequency (sharks are very attracted to squid scent). If a silky is hooked, the best practice is to cut the line promptly. If the shark is small enough and at the surface, some crews will use a de-hooker to flip the hook out without bringing the shark aboard. If the shark is large, it’s safer to cut the line near the hook. These practices improve the odds that the shark survives (studies show many silky sharks can survive if released in good condition).
• National initiatives complement WCPFC rules. For example, some Pacific Island countries have established shark sanctuaries or national prohibitions on shark retention in their EEZs, reinforcing the Commission’s no-retention rule. In those zones, any silky shark caught must be released, and fisheries patrols keep an eye out for illegal finning. Such national laws can apply even to small-scale coastal fisheries, tackling mortality sources beyond just the industrial tuna fleets.

Monitoring and compliance

• Observer coverage in purse seine fisheries (currently near 100% for licensed vessels) has been crucial to monitoring silky shark outcomes. Observers record how many sharks are seen, how many are released alive, and the condition upon release. These data show improved handling in recent years, but also reveal that a large portion of silky sharks caught in FAD sets may be dead before release (due to stress or entanglement). This underscores the need to keep working on preventative measures (like better FAD design and possibly limits on FAD sets in areas of high silky abundance).
• In longline fisheries, where observer coverage is low (~5%), there is uncertainty about the true magnitude of silky shark catches and how consistently they are being released. WCPFC is promoting the expansion of electronic monitoring on longliners, which could verify that vessels are not secretly retaining silky sharks (e.g., cutting off fins for later sale). Compliance audits have occasionally found silky shark fins in vessel inspections, indicating some violations. The Commission has urged all members to ensure the no-retention rule is enforced through their domestic laws and to prosecute offenders.
• Scientists continue to recommend updated stock assessments for silky sharks in the Pacific. Improved data collection (such as genetic sampling of caught/released sharks to identify population structure, and tagging studies to track movements and survival) is needed. The WCPFC Shark Research Plan identifies silky sharks as a priority species for updated abundance indices and bycatch mitigation research, to gauge whether current measures are sufficient or if additional actions (like time-area closures around pupping grounds, or gear innovations) might be warranted.

Ecology and fishery interaction

• Whale sharks inhabit open oceans as well as coastal regions, following blooms of plankton and small fish. In the WCPO, they are often sighted in the tropics (10°N–10°S) but can range into subtropical waters seasonally. They have predictable aggregation sites in some areas (for example, parts of Micronesia or the Coral Triangle) where they come to feed. Tuna purse-seine fisheries overlap with whale shark habitat particularly in equatorial surface fisheries. When a whale shark is present under a school of tuna, the tuna tend to stay with the shark, which historically made it an attractive “natural FAD” from a fishing perspective. Unfortunately, when a purse seine is set around the school, the whale shark can become trapped. Given their massive size (up to 12+ meters), handling them is extremely challenging and dangerous if not done carefully. In a few documented cases, whale sharks tangled in nets have died from stress, injury, or inability to move water across their gills.
• It’s worth noting that whale sharks spend a lot of time near the surface (often basking or feeding), which is why they frequently cross paths with surface fishing gear and vessels. They can dive to great depths but generally come back to surface waters where food is abundant. They do not evade nets or boats quickly, which makes them easy to capture inadvertently. Whale sharks are plankton-eaters and do not bite bait, so interactions with longlines are almost nil – the main risk in longlining might be if a whale shark gets entangled in a line or if a longline vessel strikes one at the surface, but these are very rare events.

Safe release practices

• When a whale shark is spotted inside a purse seine, best practice is to stop the net from closing further and avoid bringing the shark alongside the power block. WCPFC guidelines suggest slowing down the winch and keeping the whale shark in an area of the net with sufficient water (so it can continue swimming). Many fleets use a “lowering the corks” method: one section of the corkline (top of the net) is dropped to create an escape opening large enough for the whale shark to swim out on its own. This method has proven effective, particularly for energetic sharks that can navigate out when given the chance.
• If the shark is exhausted or entangled, crews may employ a more hands-on approach. For smaller whale sharks (juveniles), a few strong crew members might enter the water or lean over the skiff to carefully cut any net wraps and guide the shark out or even lift it with a stretcher if feasible. For large individuals, cutting the net may be a last resort to free the animal – some companies accept the cost of net damage as a trade-off for saving an endangered animal. In all cases, minimizing the handling time is critical: whale sharks can suffer internal injuries or become fatally stressed if restrained too long. Crews are trained to never tie ropes around the shark or pull it by the gill slits or tail (practices that have caused fatalities in the past). Instead, the emphasis is on gentle guiding and patience.
• After a release, observers note the condition of the whale shark (e.g., “swam away strongly” vs “weak or injured upon release”). This information helps assess how effective current release techniques are. Some collaborative programs also tag whale sharks that have been encircled and released, tracking their movements and survivorship post-interaction. These studies suggest that whale sharks can survive a net incident if released properly, though injuries like abrasion or temporary behavioral changes have been observed.

Monitoring and cooperation

• The reporting of whale shark interactions to WCPFC is mandatory. Annual reports by members include details such as the number of sets where whale sharks were present, how many were released alive, and any mortalities. This data shows that the incidence of whale shark capture is relatively low (a small percentage of FAD sets involve a whale shark), and since the prohibition on intentional sets was enacted, reported mortality has decreased. Nonetheless, even a handful of deaths is concerning for such a slow-growing species, so WCPFC continues to refine measures.
• Cooperation with the IATTC (Inter-American Tropical Tuna Commission) in the Eastern Pacific has been important, since whale sharks traverse the whole Pacific. Both RFMOs now have similar rules against setting on whale sharks, ensuring that vessels on either side of the 150°W boundary operate under consistent conservation measures. Additionally, WCPFC members support global efforts like the International Whale Shark Photo-ID database and CITES Appendix II listing (which regulates international trade in whale shark products) to safeguard the species beyond just fisheries rules.
• On a national level, many Pacific countries have turned whale sharks into valuable assets for tourism rather than as bycatch. For instance, places like Palau and Fiji have shark sanctuaries that ban all shark catches, including whale sharks, in their waters. These broader protections complement WCPFC’s measures on the high seas, creating safer migratory corridors. Continued education of fishing crews about the ecological and economic importance of live whale sharks (as tourism draws) further incentivizes careful release.

Distribution and catch

• Blue sharks have a cosmopolitan distribution, mostly in open ocean waters between roughly 50°N and 50°S. They prefer cooler temperate waters compared to many tropical sharks, which is why they are especially common in the North Pacific transition zone and in subtropical regions. In the WCPO, significant blue shark bycatch comes from longline fleets operating in the North Pacific (Japan, Taiwan, USA, etc.) targeting swordfish and tuna. They are often caught in cooler-water fisheries targeting albacore tuna as well. Blue sharks undertake long migrations and have been tracked crossing entire ocean basins. This means the WCPO stock likely mixes with the Eastern Pacific, making international cooperation important.
• In longline fisheries, blue sharks are often caught on deeper sets (they are known to dive deep during the day and come closer to the surface at night). They readily take a variety of baits. Because they are more robust (physically) than species like hammerheads or threshers, a fair number of blue sharks survive the hauling process, especially if the soak time is not too long. Some are brought onboard alive and then either released or landed for sale. In contrast to purse seine fisheries – which very rarely catch blue sharks since these sharks don’t typically aggregate under FADs – the vast majority of blue shark mortality in the WCPO comes from longlines. There is also likely unreported mortality from illegal fishing or artisanal gillnet fisheries in some regions.
• Due to their prevalence, blue sharks have historically been an important part of shark fin trade (their fins are of medium-high value) and also used for meat (often sold as cheaper shark meat or processed into products like fish balls). However, increased regulations and declining fin prices have reduced targeted effort on blue sharks. Now they are mostly utilized when caught incidentally. Still, given the large catches (tens of thousands per year in WCPO reported, possibly more unreported), even moderate mortality rates need monitoring to ensure the population remains healthy.

Best practices and fleet actions

• Some WCPFC members have adopted voluntary measures in their longline fleets to minimize unnecessary blue shark mortality. For example, certain fleets encourage the release of live blue sharks, especially juveniles or pregnant females, since the species has relatively good survival chances if released promptly. Where market demand for blue shark is low, skippers may prefer to cut sharks off the line to save space and time (which incidentally benefits the shark if it swims away). Making use of circle hooks (which tend to hook fish in the mouth) can also reduce internal injuries in sharks, meaning those that are released have a better chance of survival.
• Japan, the U.S., and other nations have developed shark management plans that include blue sharks. These often feature measures like trip limits (e.g., capping how many can be landed per trip to deter targeting) or bycatch ratio limits (sharks can only make up a certain percentage of the catch). Such measures keep blue shark retention at moderate levels. Additionally, if observers notice a particularly high shark bycatch in a set or area, some vessels will move to a different area to avoid continuous shark catches (this is more common when shark catches are interfering with fishing operations by tangling gear or biting off target fish).
• Research into gear modifications is ongoing. Trials of electropositive metals or magnets on hooks (which theoretically repel sharks) have had mixed results but could one day help reduce blue shark catch without affecting tuna. Also, time-of-day adjustments – for example, setting longlines only at night at depths where tuna are present but blue sharks might be less active – are being explored. However, given blue sharks’ wide vertical and horizontal range, completely avoiding them while tuna fishing is challenging. A combination of moderate retention with full utilization and selective release seems to be the practical strategy at present.

Data and stock assessment

• The North Pacific blue shark stock assessment is updated periodically by the ISC. The 2018 assessment was cautiously optimistic, but it highlighted data gaps such as uncertainties in historical catch (particularly before the year 2000) and the need for better reporting of discards. Efforts are underway to improve species-specific logbook reporting and to integrate observer data into catch estimates. The South Pacific stock is less studied; WCPFC’s Scientific Committee has encouraged collection of more data from southern hemisphere fleets and potentially a separate assessment or analysis for that region if enough data become available.
• WCPFC is also working on shark indicators (simple metrics like catch per effort or average size) as interim measures of stock health between assessments. For blue sharks, tracking trends in these indicators can alert managers to any sudden changes. For instance, if observers start seeing fewer blue sharks per 1000 hooks than before, or a shift to mostly smaller individuals, that could signal overfishing, prompting a management response even before a full assessment is done.
• International management of blue sharks may eventually include explicit quotas or limits if warranted. The challenge is balancing the fact that blue sharks are currently relatively plentiful (so imposing strict limits might be seen as unnecessary by some fishing nations) versus the precautionary approach given their importance in the ecosystem and value in fisheries. WCPFC’s current stance is to closely monitor and encourage responsible fishing rather than hard limits, but this could evolve with new scientific evidence.

Distribution and catch profile

• Shortfin makos are found throughout the Pacific but are most common in temperate and subtropical waters. In the WCPO, higher catch rates occur in the subtropics (~20–40° latitude) rather than in equatorial waters. Longline fisheries targeting species like albacore, bigeye tuna, or swordfish incidentally catch makos, particularly when using steel leaders (now banned) or when fishing shallower sets where makos hunt. Makos are powerful and often still alive when brought to the vessel; they can even damage gear or injure crew if not handled carefully. Because of their value, many were historically kept rather than released. In some regions (for instance, off New Zealand or Japan), makos are also caught by recreational anglers, though those catches are outside WCPFC’s purview, they do contribute to overall mortality.
• Makos are known to undertake long-distance movements but also show seasonal site fidelity (coming to certain regions when prey like squid or small tuna are abundant). They tend to be solitary hunters. When hooked on a longline, makos often put up a fierce fight, which can lead to fatigue; however, they also have a relatively high chance of surviving capture if handled properly because they must keep water flowing over their gills (ram ventilation) to breathe, and the act of being pulled by the line can suffice if not too long. That said, if a mako is hooked and struggles for many hours, it can die on the line from exhaustion. Observer data indicates a mix of outcomes: some makos are dead on retrieval, others come aboard thrashing.

Bycatch mitigation and handling

• With wire leaders no longer allowed, many makos that would have been firmly hooked can now sometimes escape by biting off monofilament leaders. While fishermen losing a potentially valuable catch may not favor that, it is a conscious compromise to aid shark conservation. Crews are encouraged to release makos that do come up alive: one common practice is to cut the branch line as soon as the shark is at the surface, to avoid having to bring it on deck at all. This eliminates the danger to crew and increases the shark’s survival odds (since less time out of water and less stress). If a mako is brought on deck (intentionally or accidentally), extreme caution is needed – crew often cover the shark’s eyes with a cloth and secure the tail with a rope to control it while the hook is removed. Some fleets have barbless hooks or use bolt-cutters to simply cut the hook shank and let the shark go, rather than trying to pry the hook out.
• Avoidance measures are not well-developed for makos specifically, but some ideas include temporal closures if areas of high mako catch are identified. For example, if data show a certain quadrant of the ocean has seasonally high mako interactions, the Commission could advise fleets to limit effort there during those times (this is not yet in place, but it’s an option). Another possible mitigation is incentivizing the use of “hook timers” or similar devices that can indicate a big catch early – if a mako is hooked, some smart gear might alert fishermen who could then choose to retrieve the line sooner to release the shark before it dies. These technologies are still experimental.
• The role of education is also important: WCPFC and NGOs have provided materials to fishing crews illustrating how to identify mako sharks (to differentiate shortfin vs longfin mako, though longfin is very rare in WCPO, nearly all are shortfin) and the importance of their conservation status. By fostering a conservation ethic (similar to how many crews have learned to care about releasing sea turtles or seabirds), the hope is that fishers will see live release of makos not just as a rule but as the right thing to do when feasible.

Research and future management

• Data collection on mako sharks in the WCPO is being improved through initiatives like biological sampling (e.g., collecting vertebrae for age and growth studies, reproductive organs from any dead specimens to understand maturity). The Shark Research Plan under WCPFC specifically lists mako age/growth and catch history improvements as priorities. One outcome expected in coming years is a new Pacific-wide assessment or at least a productivity-susceptibility analysis to gauge how current fishing levels might impact makos in the long term.
• International cooperation is crucial since makos move across management boundaries. WCPFC liaises with the IATTC and ICCAT (Atlantic) to share knowledge on effective measures. For example, ICCAT recently adopted a no-retention measure for North Atlantic makos due to severe depletion there; while the Pacific situation is less dire, WCPFC is watching that case closely. If the Pacific stock shows signs of decline, WCPFC may follow suit with stricter measures. The CITES listing of makos in 2019 has already prompted better record-keeping; countries must demonstrate exports are sustainable. This effectively pushes WCPFC members to limit mako catch to sustainable levels or risk losing export markets.
• The next few years will likely see WCPFC discussing the idea of explicit mako catch limits or a move to mandatory live release. The balance will hinge on scientific evidence and the willingness of fishing nations to forego some short-term catch for long-term conservation. Given the mako’s value, any proposal for full no-retention could be contentious – some members may prefer setting a quota or minimum size (to protect juveniles) as an alternative. The Scientific Committee’s advice will be central: if they advise, for instance, that a X% reduction in mortality is needed to keep the stock healthy, the Commission can then debate the best way to achieve that (be it a ban on retention or gear/effort controls).

Behavior and bycatch characteristics

• Bigeye threshers, true to their name, have large eyes adapted for low-light conditions, allowing them to hunt in deep water. They typically spend daylight hours at depths of 300–500 m and come closer to the surface at night to feed on squid and small fish. Longline sets that soak overnight can intercept them during these vertical movements. Once hooked, threshers are not as vigorous as makos, but their chances of survival are slim. Studies have shown extremely high physiological stress in threshers upon capture (they often exhibit something akin to fatal shock). This is one reason that simply mandating release, while important, may not substantially reduce mortality – avoidance of capture is more critical.
• The other thresher species (common and pelagic) are more coastal or epipelagic, so they are less encountered in high-seas tuna fisheries, though some bycatch does happen near continental shelves or island chains. Common threshers tend to stay closer to coasts and are more often caught in coastal gillnets or by recreational fisheries than by longliners in the open ocean. Pelagic threshers overlap with bigeye threshers in some tropical offshore areas but are generally smaller and may not bite the larger hooks used in tuna longlining as frequently. Nonetheless, any thresher sighted in the catch is treated with the same concern due to their poor survival prospects.

Mitigation options

• Reducing thresher shark bycatch is challenging. One practical step is temporal/spatial avoidance: identify hotspots where bigeye threshers are commonly caught (for example, certain seamount areas or convergence zones) and advise vessels to avoid those if possible. If a vessel notices multiple threshers in consecutive sets, they might shift location to prevent additional mortalities. However, because thresher encounters are relatively rare events scattered across a huge ocean, a broad-based measure like an area closure is hard to justify unless a very clear hotspot is identified.
• Gear modifications might help to a degree. Using slightly deeper hook deployments could miss some threshers that stay above certain depths. Additionally, circle hooks might reduce the likelihood of a thresher being deeply hooked – possibly leading to more bite-offs (the shark escaping) or at least a mouth hooking that could be removed. Some research suggests that bigeye threshers are caught predominantly on the shallowest hooks of deep sets; thus, removing the shallowest few hooks (a measure analogous to turtle mitigation) could reduce thresher catch. WCPFC has not mandated this, but individual fleets aware of high thresher bycatch have experimented with avoiding placing hooks near floats.
• On the handling side, for the minority of threshers that are found alive, gentle release is still encouraged. Crew should not gaff or lift the thresher by the tail (despite the tail being long, it’s fragile and full of muscles the shark needs). The proper method is to cut the line near the hook or use a de-hooker if the hook is accessible and the shark is docile. Because threshers have smaller teeth and are not aggressive to boats, sometimes crew can safely reach the hook with a pole. But again, since most are dead, the emphasis must be on avoiding getting them on the line in the first place.

Data and monitoring needs

• A significant gap is the lack of comprehensive data on thresher catch and mortality. Many longline fisheries historically did not report shark species at fine resolution, so catch records often lump threshers into an “other sharks” category. Observer programs have improved this, but coverage is low. To address this, WCPFC’s Shark Research Plan includes projects to reconstruct thresher catch histories using available data and extrapolation. By estimating how many threshers were likely caught in the past decades, scientists can gauge the extent of decline and current exploitation rates.
• There is interest in conducting a Pacific-wide assessment for bigeye thresher (the most relevant species for high seas). Such an assessment would require pooling data from multiple RFMOs and national sources. WCPFC scientists are collaborating with IATTC and ICCAT scientists since these sharks span oceans. Even if a full assessment is not feasible, a qualitative risk assessment has rated bigeye thresher as one of the most vulnerable shark species in tuna fisheries, reinforcing the call for precautionary management.
• In terms of management next steps, the WCPFC could consider a proposal similar to other RFMOs – an explicit ban on retaining any thresher sharks (Alopiidae) caught in its Convention Area. This would harmonize the Pacific with the Atlantic and Indian Ocean measures and send a clear signal to fishers. The downside (as noted) is that nearly all thresher bycatch are dead discards, so a no-retention rule mainly serves to prevent any incentive to target them or sell them. It’s a necessary piece, but not sufficient to reduce mortality. Therefore, it would likely be coupled with continued gear and effort measures, plus international cooperation on protecting critical habitats (like nearshore nursery grounds for threshers, often within national EEZs).

Habitat and bycatch patterns

• Scalloped hammerheads primarily inhabit continental shelves, island terraces, and coastal zones, but juveniles and subadults can venture into the open ocean, especially in areas with mesoscale eddies or convergence zones that concentrate food. These young hammerheads sometimes end up around FADs or debris lines, which explains why purse seiners have occasionally caught them. Observer records show that such events are rare but not absent – usually single-digit counts of small hammerheads in FAD sets in a given year across the WCPO. Longline interactions are also infrequent; when they occur, it’s often on fleets operating near the edges of EEZs or seamounts where hammerheads roam in deeper water. Great hammerheads, being larger and more solitary, are even less encountered offshore; a few have been recorded by observers on longlines, generally in subtropical areas. Smooth hammerheads prefer temperate waters and are occasionally caught by temperate longliners, but they too are not a common catch compared to blues or makos.
• Hammerheads that do end up on a line or in a net have very low survival odds. Scalloped hammerheads, if tangled in a net or kept on a line for any length of time, often suffocate due to their high oxygen demand and sensitivity. Even if alive at release, post-release mortality is suspected to be high; satellite tagging studies in other regions found many tagged hammerheads died shortly after release from longlines, likely from capture stress. This makes prevention of capture the critical goal. Also, because hammerhead fins are still valuable on black markets, there is a risk that if one is caught and already dead, crew might be tempted to retain the fins. Strict enforcement (through port inspections and observer oversight) is essential to ensure even dead hammerheads are not kept. Instead, they should be discarded (with documentation) to remove any profit motive.

Risk reduction and best practices

• For purse seine fisheries, one protective measure is the move to non-entangling FADs, as previously mentioned. Old-style FADs with loose netting were known to entangle various marine life, including small hammerheads that might investigate the FAD. Eliminating that risk helps. Purse seine skippers are also made aware that if a hammerhead is seen in the net, it should be a priority to release; because hammerheads can be dangerous (they can bite if handled incautiously) but also fragile, the recommended method is to gently guide them out of the net opening or use a dip net for very small ones. Direct lifting by the cephalofoil (the “hammer” head) or by the tail is discouraged as it can injure the shark.
• Longline fleets can reduce incidental hammerhead catch by avoiding known coastal hotspots, especially nursery areas. For instance, scalloped hammerheads have nursery areas in parts of Indonesia, the Philippines, and some Pacific Islands – ensuring longline effort is minimal in adjacent offshore waters during pupping season can help. Some RFMOs have suggested gear modifications like circle hooks could improve survival if a hammerhead is hooked (by reducing bleeding), but given hammerheads’ low survival regardless, gear changes have a limited effect. The best practice remains: if a hammerhead is on the line and alive, release it immediately by cutting the line (ideally leaving minimal trailing line). If it’s found moribund or dead, crew should still not retain any part – showing that even a dead specimen has zero value to them enforces the conservation ethic.
• Another important aspect is training and identification: hammerhead sharks are easy to recognize due to their head shape, and crew/observers must distinguish them from other shark species. Misidentification isn’t common for hammerheads, but it’s critical that any catch of these species is logged properly given their rarity. Some programs have encouraged fishers to collect a small tissue sample from any dead hammerhead (if safe to do so) for genetic analysis; this can help scientists determine which population (e.g., which breeding stock) the shark came from. Such information might reveal, for example, that hammerheads caught in the high seas originated from a particular coastal nursery, highlighting where conservation efforts should focus.

Conservation outlook

• Hammerhead conservation largely depends on what happens in coastal waters (juvenile nurseries) where most are caught. Nevertheless, WCPFC’s role in eliminating additional high-seas mortality is important. A proposal for a hammerhead-specific measure could re-emerge, aiming to formally prohibit retention Commission-wide. Given the critically endangered status, this would likely be supported by the scientific community. Harmonizing WCPFC’s approach with other RFMOs (which already ban hammerhead retention in many cases) ensures that no ocean region is a loophole for hammerhead exploitation.
• The Commission also collaborates with organizations like the Secretariat of the Pacific Regional Environment Programme (SPREP) and national wildlife authorities to raise awareness about hammerhead status. Capacity-building workshops for fisheries observers often include modules on handling and recording interactions with endangered species, including hammerheads. Observers in some Pacific Island fleets have begun tagging any hammerheads they release (if alive) with archival tags to gather more data on their fate and movements. Although sample sizes are small, each data point is valuable for such a rare encounter species.
• Ultimately, the hope is that through a combination of zero retention, improved bycatch mitigation, and strong coastal protections, hammerhead shark populations might eventually stabilize or recover. However, given their biology, any recovery will be a slow, multi-decade process. The immediate aim is to halt further declines. WCPFC’s strengthening stance on shark bycatch indicates that hammerheads will remain a high priority in the coming years, with management measures likely to become more stringent if current efforts are deemed insufficient.