Saltwater · Summer peak in ports and rocky shallows; juvenile balls most conspicuous in mid-summer

Striped Eel-catfish

Plotosus lineatus

A striped, eel-like saltwater catfish and the number-one dangerous bycatch of summer night fishing in Japanese ports. Its dorsal and pectoral fin spines are venomous and serrated: never grab it bare-handed. Juveniles roll together in dense balls, the famous 'gonzui-dama'. Safe identification and safe unhooking are the core of this page: if in doubt, cut the line and never hold the fish.

Seasons · Peak

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

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Oct

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Dec

Striped Eel-catfish — Photo: Fernando Losada Rodríguez, CC BY-SA 4.0 — Wikimedia Commons

Identifying features

Long eel-like body with brown colour and pale creamy longitudinal stripes, vivid in juveniles
Eight whisker-like barbels around the mouth (four pairs)
Venomous serrated spines at the front of the dorsal fin and on each pectoral fin — the key danger point
Long rear dorsal and anal fins merging around the tail, giving the eel-like look
Juveniles are boldly striped; the stripes fade with age

Habits

Juveniles form dense rolling balls called 'gonzui-dama' — an unmistakable summer sight
Feeds at night on small crustaceans, worms and dead matter on the bottom
Hides among rocks and under ledges by day
Adults lose the bold stripes and become plainer brown
Schools pack tightly together, juveniles in balls and adults in loose groups

Distribution

Regional coverage expanding

Where to find them

Summer night port piers in Sagami Bay
Boso Peninsula harbours and rocky shallows, Chiba
Seto Inland Sea ports and rocky bays in summer

Where they live

Sand and mud bottom inside ports and harboursRocky shallows and reef edgesEstuary mouths and quiet bay corners

How to catch them

Port night bottom fishing — the classic encounter Shore

Rig: Light bottom rig with a small hook aimed at other species, fished at night from a pier, where gonzui bite regularly

Bait/lure: Shrimp or squid pieces on the bottom

Key tip: Work the hook free with long pliers held away from the body and release without touching the spines — if in doubt, cut the line.

Rocky-shallow rigs where gonzui shelter Shore

Rig: Small bottom rig with size 6-10 hooks placed in rocky shallows and reef edges on summer evenings

Bait/lure: Small crab or shrimp pieces among the rocks

Key tip: Approach the hook only when the fish is still; the spines point outward even on dead fish — keep distance at all times.

Best baits & lures

Shrimp piecesSquid stripsSmall crab or shellfish pieces

Techniques for Striped Eel-catfish →

Baseline setup

Rod: Light to medium pier or shore spinning rod
Line: 10-20 lb line on pier bottom rigs
Terminal: Long-nose pliers or a dehooker and heavy gloves for safe release; spare rigs

Recommended gear for this species

Rod · Best value

9' 5-weight fly rod outfit

≈ US$180-260

Covers chironomid lakes and small rivers with one setup.

Flies · Budget

Chironomid assortment (30 patterns)

≈ US$25-40

Chironomids are 60% of a lake rainbow's diet in spring.

Picks come from our rule library — never paid placements. Prices are guides; affiliate links may earn us a commission.

Typical size

Common 6-8 in (15-20 cm); large fish to about 12 in (30 cm)

On the table

Caution — the flesh is eaten in parts of Japan only when handled with complete confidence, but the venomous spines make it a poor choice for most anglers. Most are released carefully; never let the spines touch skin.

Similar species

Japanese Bagrid CatfishThe japanese-bagrid-catfish is a pure freshwater species of rivers and lakes; the striped eel-catfish lives in saltwater ports — both carry venomous spines, but only the eel-catfish has the long longitudinal stripes and eel-like tail

Regulations vary by area and can change in-season — always check the official rules for your area before you fish. Regulations guide →

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