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101-acre lake near Scottish Borders. The lake tops out around 41 ft. The depth chart comes from published agency bathymetric survey data, so the contours are survey-derived rather than computer-modeled. The depth data here comes from Murray & Pullar's Scottish loch survey of 1903, digitized from the bathymetric atlas published in 1910. The rest of this page walks each species through its year, using the map's own scoring.
The drawn water covers 101 acres wrapped in 1.7 miles of bank. At index 1.2 the outline is almost a bowl — read the depth changes, not the shoreline. Roughly 81% of the water is 15 ft or less, the band where the food chain lives. End to end it runs roughly 0.7 mi, about 0.4 mi across. Scottish Borders claims this one. Its nearest charted neighbour, Gladhouse Reservoir, is 3 mi to the northeast.
Start shallow in spring: brown trout sit in 3 to 25 ft that time of year. Summer pushes them deeper, 12 to 41 ft, and winter fish settle into 5 to 35 ft. The spot to know is Deep basin, a deep basin in about 41 ft of water that rates prime for brown trout in summer. Warm-month bites cluster around after dark and early morning. Throw a spoon at the thermocline or a deep stickbait (night) until the fish tell you otherwise.
Depth note: when a documented seasonal range extends below this chart, the table shows the deepest mapped working water, not a verified holding depth.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 3 to 25 ft | dawn & dusk | Secondary point (6 ft) | Stickbait off planer boards (shallow), Small spoon along mud lines |
| Summer | 12 to 41 ft chart-limited; documented 25 to 60 ft | night & dawn | Deep basin (41 ft) | Spoon at the thermocline, Deep stickbait (night) |
| Fall | 5 to 30 ft | dusk & dawn | Secondary point (6 ft) | Jerkbait over gravel, Casting spoon |
| Winter | 5 to 35 ft | dawn | Break off the point (2 ft) | Jigging spoon, Small stickbait (slow) |
When the water first warms, european perch slide up into 3 to 12 ft. By summer they slide out to 8 to 28 ft, and by winter most fish are in 12 to 33 ft. If you only fish one area, make it Shallow bay flat: a weed flat around 2 ft that scores prime in spring. In summer the feeding windows fall in early morning. Keep a drop-shot micro plastics or a small crankbait (perch pattern) rigged through the warm months.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 3 to 12 ft | midday & dawn | Shallow bay flat (2 ft) | Small jig + curly tail, Inline spinner #1-2 |
| Summer | 8 to 28 ft | dawn | Break off the point (2 ft) | Drop-shot micro plastics, Small crankbait (perch pattern) |
| Fall | 10 to 33 ft | midday | Deep basin (41 ft) | Jigging spoon (small), Drop-shot on deep flats |
| Winter | 12 to 33 ft | midday & dawn | Deep basin (41 ft) | Tungsten jig + maggots, Small balance jig |
Spring northern pike on Portmore Loch hold shallow, usually 2 to 8 ft. By summer they slide out to 8 to 20 ft, and by winter most fish are in 5 to 15 ft. The chart's best answer is Shallow bay flat — weed flat, 2 ft, prime for spring. Prime time lands in early morning and the evening. The summer box starts with a bucktail or a weedless spoon over cabbage.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 2 to 8 ft | midday & dawn | Shallow bay flat (2 ft) | #5 inline spinner, Spoon (red/white) |
| Summer | 8 to 20 ft | dawn & dusk | Secondary point (6 ft) | Bucktail, Weedless spoon over cabbage |
| Fall | 6 to 18 ft | midday & dawn | Secondary point (6 ft) | Big rubber (Bull Dawg style), Husky-style jerkbait |
| Winter | 5 to 15 ft | midday | Secondary point (6 ft) | Tip-ups, Large jigging spoon |
Spring puts arctic char in skinny water — 4 to 15 ft is the zone. Warm water sends them out to 12 to 41 ft; cold water stacks them in 10 to 40 ft. Deep basin is the standout, a deep basin at roughly 41 ft, rated prime for summer arctic char. Plan around early morning in the warm months. A jigging spoon vertical or a tube jig (smelt) covers the summer program.
Depth note: when a documented seasonal range extends below this chart, the table shows the deepest mapped working water, not a verified holding depth.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 4 to 15 ft | midday & dawn | Break off the point (2 ft) | Small casting spoon (silver/orange), Jerkbait (small) |
| Summer | 12 to 41 ft chart-limited; documented 20 to 60 ft | dawn | Deep basin (41 ft) | Jigging spoon vertical, Tube jig (smelt) |
| Fall | 8 to 30 ft | midday & dusk | Break off the point (2 ft) | Casting spoon (orange/gold), Beadhead streamer |
| Winter | 10 to 40 ft | midday & dawn | Deep basin (41 ft) | Jigging spoon (glow/silver), Tungsten jig + plastic |
Come spring, look for rainbow trout tight to the bank in 5 to 20 ft. They move out to 8 to 30 ft in summer and finish the year down in 8 to 40 ft. If you only fish one area, make it Secondary point: a point around 6 ft that scores prime in spring. Best bite is early morning and the evening. A dodger + spoon (deep troll) or a flutter spoon is the honest summer answer here.
| Season | Depth | Best window | Start at | Go-to baits |
|---|---|---|---|---|
| Spring | 5 to 20 ft | dawn & dusk | Secondary point (6 ft) | Inline spinner (silver), Small spoon |
| Summer | 8 to 30 ft | dawn & dusk | Secondary point (6 ft) | Dodger + spoon (deep troll), Flutter spoon |
| Fall | 10 to 35 ft | dawn & dusk | Secondary point (6 ft) | Casting spoon, Jerkbait over shoals |
| Winter | 8 to 40 ft | dawn | Deep basin (41 ft) | Jigging spoon, Tube jig (white) |
Count 6 structure marks on this chart. The deepest, Deep basin, sits near 41 ft.
Portmore Loch is about 41 ft (12 m) deep at its deepest point. The depth data here comes from Murray & Pullar's Scottish loch survey of 1903, digitized from the bathymetric atlas published in 1910.
Anglers target brown trout, european perch, northern pike, arctic char, rainbow trout on Portmore Loch. This isn't a survey of the water — none is published for it — but an informed estimate from the species common to the region, narrowed by this water's depth, size and each species' range.
Shallow bay flat is the top-rated area: a weed flat in about 2 ft of water that rates prime for northern pike in spring. The map above holds the full rated-spot list for every species and season.
For brown trout, the summer bite is best in after dark and early morning. Each species page section below lists the seasonal windows, and the map shows a live NOW badge when you're inside one.
Gladhouse Reservoir 3 mi · Rosebery Reservoir 5 mi · Edgelaw Reservoir 6 mi · Slipperfield Loch or Dalmahoy Loch 8 mi · Threipmuir Reservoir 10 mi · Harlaw Reservoir 10 mi · Harperigg Reservoir 12 mi · Loch Eddy 12 mi · Duddingston Loch 14 mi · St Marys Loch 18 mi · Talla Reservoir 20 mi · Headshaw Loch 21 mi
See how Portmore Loch stacks up: best northern pike lakes in United Kingdom · best european perch lakes in United Kingdom · best brown trout lakes in United Kingdom · best arctic char lakes in United Kingdom
More water nearby: Scottish Borders fishing maps (7 charts). Browse all United Kingdom fishing maps. See every water on DepthScout. Bathymetry: published agency survey data. How we build these maps. Fish here with a sonar unit that logs? Send us your depth data and we'll improve this chart, credited to you. For fishing guidance only, never navigation.