Invasive species, and where spearfishing genuinely helps
Explainer · Last reviewed 2026-08-27
Targeted removal of an invasive predator is the one situation where spearfishing is used as a management tool with evidence behind it — and the evidence is also clear that the effect is local and needs sustained effort.
Safety: venomous and spined species — can cause injury needing treatment. 4 more points apply here.
Never dive alone, dive one up one down, and never extend a dive for a fish.
This is the strongest environmental claim available to this discipline and it is routinely overstated, which is a shame, because the accurate version is impressive enough.
THE CASE THAT WORKS: LIONFISH. Indo-Pacific lionfish are established across the western Atlantic, Gulf of Mexico and Caribbean. They consume large numbers of small native reef fish, they reproduce prolifically, and they have no significant native predators there. Divers removing them is used and encouraged as a management measure, organised through derbies, programmes and in some places a commercial market for the fillets.
WHY SPEARFISHING SUITS THE PROBLEM. The removal has to be species-specific — a net or trap on a reef would take everything — and lionfish are approachable, distinctive and shallow enough for breath-hold divers over much of their range. A method whose defining property is choosing the individual is, for once, exactly the right tool.
WHAT THE EVIDENCE ALSO SAYS, and this half is usually dropped. The effect is LOCAL and depends on SUSTAINED EFFORT. Removal at a site suppresses density at that site while people keep doing it; stop, and it returns. Populations at depths beyond diver range act as a reservoir. Nobody is eradicating this invasion by diving, and describing removal as solving it overstates what has been shown.
WHAT DOES NOT FOLLOW. That spearfishing is good for reefs generally. The lionfish case works precisely because the target is a species with no native ecological role in that system — the exact opposite of the situation for every native fish a diver might take. Generalising from it is the commonest error in advocacy for the method, and the error is not improved by being made sincerely.
Other invasions, and why the lionfish case does not transfer automatically
Invasive fish are not all lionfish, and the reasoning has to be redone each time.
WHAT MAKES DIVER REMOVAL PLAUSIBLE for a given species: it is reliably identifiable underwater, it occurs within breath-hold depth, it is approachable, it does not disperse when disturbed, and removing individuals actually reduces local density rather than freeing space that is refilled from elsewhere.
WHERE THOSE CONDITIONS FAIL, removal is effort without a measurable outcome — which is not harmful, and is also not conservation.
AND THERE IS A RISK WORTH NAMING. A programme that encourages removal of an invasive species depends entirely on divers identifying it correctly. Several invasive species have native lookalikes; a removal campaign that produces misidentified native fish has done harm in the name of help. This is the identification rule again, and it does not relax because the intention is good.
THE OTHER DIRECTION: DIVERS AS A VECTOR. Equipment moves between waters carrying water, mud and organisms, and freshwater diving in particular carries the same biosecurity obligations as any other freshwater activity. Drying equipment thoroughly is the control that does most of the work. A diver removing an invasive species in one water and introducing another to the next has not come out ahead.
Backed by research — why, and the sources (2)
Supported by peer-reviewed research or fisheries science. The sources are listed and can be checked.
- NOAA research and management guidance on the invasive Indo-Pacific lionfish — NOAA National Centers for Coastal Ocean Science (Scientific institute)Relied on for: Lionfish invasion in the western Atlantic and Caribbean and diver removal as a local management measure requiring sustained effort.States this directlyCitation checked — the work exists and is described correctly
- Check Clean Dry — biosecurity guidance for water users — GB Non-native Species Secretariat (Conservation authority)Relied on for: Biosecurity practice for water users, including the movement of organisms on equipment and the role of drying.States this directlyPassage read and verified
What management is trying to control, stated neutrally
Regulation around invasive species usually pursues three separate objectives, and they are worth telling apart because they sometimes conflict.
SUPPRESSION at sites of high conservation value, which is what removal programmes are for.
PREVENTION OF FURTHER SPREAD, which is about vectors — ballast water, the aquarium trade, equipment movement — and where individual divers matter most.
AVOIDING PERVERSE INCENTIVES. This is the subtle one. Creating a market for an invasive species can produce an interest in its continued presence, and management bodies think about that when deciding how to encourage removal.
FishingHQ takes no position on whether any of these is being done well anywhere. What it will say is that removal programmes are a management instrument with a documented rationale and documented limits, that participating in one is a reasonable thing for a diver to do, and that it is not the same thing as spearfishing being good for the environment.
Rules on taking invasive species differ from rules on native species in many places and are themselves variable. Check the current position locally.
Official guidance — why, and the sources (1)
Stated by a fisheries authority, scientific institute or recognised angling body. Authoritative, but summarising rather than demonstrating.
- Code of Conduct for Responsible Fisheries — Food and Agriculture Organization of the United Nations, Rome, 1995 (Standards body)Relied on for: Management responsibilities concerning introduced species and the effects of fishing on ecosystems.Background and mechanism onlyCitation checked — the work exists and is described correctly
Safety
Never dive alone, dive one up one down, and never extend a dive for a fish. The full set of breath-hold essentials — training, the buddy system, conditions, equipment and visibility — is on the spearfishing safety page.
Venomous and spined species — Can cause injury needing treatment
The invasive species divers are most often encouraged to take are frequently the ones that are dangerous to handle — lionfish carry venomous spines that remain hazardous in a dead fish, and a diver spearing them is bringing them close to their own body and onto a stringer.
What reduces it: Use the containment equipment the local programme specifies rather than a stringer, handle with puncture-resistant gloves and tools, and know where treatment is. A dead lionfish's spines are not safe.
Biosecurity and disease transfer — Can cause injury needing treatment
Suits, fins, floats and lines move water, organisms and fragments between waters, and freshwater diving in particular can transfer invasive plants and pathogens between systems that would never otherwise exchange them.
What reduces it: Clean, drain and dry kit thoroughly between waters, and never move live organisms or water from one system to another.
Precautions that always apply here
- Never spearfish or freedive alone.
- Dive one up, one down: one diver down, one on the surface actively watching, every single dive.
- Check, clean and dry your kit between different waters — the published guidance is 48 hours’ drying, in sunlight where possible, because a number of invasive species survive over two weeks in damp conditions. Nets, boots and wet mats move invasive species and disease more effectively than anything else anglers do.
Check the rules before you fish
Fishing laws, bylaws, access rules, seasons, bait restrictions and permitted methods vary by location and can change. Check the current rules from the relevant authority and the water you intend to fish before fishing.
Check with:
- Current national or regional law for where you are fishing
- Current local bylaws
- The relevant fisheries authority
- The landowner, club or fishery whose water it is
- Any restrictions specific to the species or the method you intend to use
Where to go next
Fish this applies to
Where it matters
Related reading
Environment and conservation
Sources and evidence
- NOAA research and management guidance on the invasive Indo-Pacific lionfish — NOAA National Centers for Coastal Ocean Science (Scientific institute)Relied on for: The invasive lionfish situation and diver removal as a management measure.States this directlyCitation checked — the work exists and is described correctly
Why the 4 connections on this page are here, and the sources
Fish this applies to
What experienced anglers do — 1 connection
Widely and independently recommended by experienced anglers and specialist sources. This is real angling knowledge, not proof: controlled evidence for it is limited, and FishingHQ records it as convention rather than as a demonstrated effect.
Red lionfish
An explainer that carries the mechanism the subject record depends on.
- CMAS technical and sporting standards for underwater activities — Confédération Mondiale des Activités Subaquatiques (Standards body)Relied on for: Breath-hold diving and spearfishing practice, training structure and safety expectations as set out by the international underwater federation.States this directlyCitation checked — the work exists and is described correctly
- BlueWater Hunting and Freediving — BlueWater Freedivers, Ventura, California, 1995 (Practitioner report)Relied on for: Spearfishing practice: approach, fish behaviour and the handling of speared fish, from a practitioner tradition distinct from the European one.States this directlyCitation checked — the work exists and is described correctly
Where it matters
Official guidance — 1 connection
Stated by a fisheries authority, scientific institute or recognised angling body. Authoritative, but summarising rather than demonstrating.
Spearfishing
A membership assertion rather than a topical one: this page teaches the discipline or its equipment, so the discipline's mandatory safety posture applies to it.
- CMAS technical and sporting standards for underwater activities — Confédération Mondiale des Activités Subaquatiques (Standards body)Relied on for: Breath-hold spearfishing as a defined discipline with its own technical, equipment and safety standards, set out by the international underwater federation.States this directlyCitation checked — the work exists and is described correctly
- DAN guidance on freediving safety, hypoxia and shallow-water blackout — Divers Alert Network (Water-safety or diver-training authority)Relied on for: That the safety requirements of breath-hold diving apply across the discipline rather than to particular equipment or techniques within it.States this directlyPassage read and verified
Backed by research — 1 connection
Supported by peer-reviewed research or fisheries science. The sources are listed and can be checked.
Spearfishing
The strongest environmental claim available to the method, stated with its limits.
- NOAA research and management guidance on the invasive Indo-Pacific lionfish — NOAA National Centers for Coastal Ocean Science (Scientific institute)Relied on for: The invasive lionfish situation and diver removal as a local management measure requiring sustained effort.States this directlyCitation checked — the work exists and is described correctly
Related reading
Official guidance — 1 connection
Stated by a fisheries authority, scientific institute or recognised angling body. Authoritative, but summarising rather than demonstrating.
Lookalike species, and why uncertainty means do not shoot
Where good intentions meet the identification rule, which does not relax for them.
- FAO Species Identification Guides for Fishery Purposes and the FAO Species Catalogues — Food and Agriculture Organization of the United Nations (Scientific institute)Relied on for: Identification by ranked diagnostic characters, and the limits of identification from general appearance.States this directlyCitation checked — the work exists and is described correctly
Environment and conservation
Official guidance — 1 connection
Stated by a fisheries authority, scientific institute or recognised angling body. Authoritative, but summarising rather than demonstrating.
Invasive species and biosecurity
Removal and vector control as the two halves of the same problem.
- Check Clean Dry — biosecurity guidance for water users — GB Non-native Species Secretariat (Conservation authority)Relied on for: Biosecurity practice for water users, the movement of organisms on equipment, and the role of drying.States this directlyPassage read and verified
How FishingHQ labels evidence is explained in the evidence policy.