Saltwater · Summer to autumn for big fish on southern rocky shores
Spotted Knifejaw
Oplegnathus punctatus
A heavyweight of southern rocky-shore 'soko-mono' bottom fishing, fished on the bottom with sea urchin and crab baits. With the barred knifejaw it forms the twin pillars of Japanese rock bottom fishing. Young fish are boldly spotted; the pattern fades with age and old males develop the famous white lips, 'kuchijiro'.
Seasons · Peak
Identifying features
- Grey body covered in dark spots that fade in old fish
- Beak-like mouth of fused teeth for crushing urchins and crabs
- Old males develop white lips, the 'kuchijiro' stage
- Deep, compressed body with steep head and thick skin
- Strong dorsal and anal fins, rounded tail
Habits
- Bottom feeder crushing sea urchin, crab and shellfish with fused beak teeth
- Holds close to reef and caves; powerful, reef-seeking fight
- Old, large fish develop white lips, called 'kuchijiro' by anglers
- Spotted pattern is bold in young fish and fades with age
- Most active in warm water; big-fish season is summer to autumn
Distribution
Regional coverage expanding
Where to find them
- Izu Peninsula south tip, Shizuoka
- Cape Ashizuri and Katsurahama coast reefs, Kochi
- Goto Islands rocky shores, Nagasaki
Where they live
How to catch them
Rock bottom fishing with sea urchin Rock fishing
Rig: Heavy bottom rig with a strong hook and heavy sinker, sea urchin or crab placed tight to reef from rocky shores
Bait/lure: Whole or halved sea urchin, or crab
Key tip: Keep the bait hard on the reef bottom and strike on the first firm pull — it crushes shell and runs for rock.
Boat bottom fishing over reef Boat
Rig: Heavy bottom rig from a boat at steep island reefs, crab or shellfish lowered to rocky bottom
Bait/lure: Crab or shellfish
Key tip: Position the boat close to the drop-off and keep the line vertical to cut snags and abrasion.
Best baits & lures
Baseline setup
- Rod: Heavy rock bottom rod (ishidai-style)
- Line: Heavy mono main line with strong leader, abrasion-resistant
- Terminal: Strong bottom rigs, large strong hooks, heavy sinkers
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 12-20 in (30-50 cm), about 2-7 lb (1-3 kg); large fish to 33 in (85 cm)
On the table
Excellent — firm white flesh prized simmered and as sashimi; a prestige rock-fishing fish.
Similar species
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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