Vancouver Island Tuna Radar (July, August, September)

Temperature map: satellite-derived NASA JPL MUR daily sea-surface temperature is sampled every 0.05° (~3-6 km). The hatched 15-18°C band is a research reference, not a fish detector.

Temperature breaks: for each ocean grid cell, compare the temperatures on either side east-west and north-south. Divide each difference by the distance between those neighbouring cells, correcting longitude distance for latitude. Combine the two rates as sqrt((east-west change)^2 + (north-south change)^2), in °C/km. A sharper colour means a stronger analysed temperature gradient. Land, missing neighbours and grid edges are masked, so a grey coastal patch does not always mean land. The colour scale is fixed at 0-0.12°C/km with higher values capped at the brightest colour for display only. There is no tuna-presence threshold or catch probability. Daily gap filling and coarse sampling can smooth, shift or miss fronts. This is an environmental clue, not the exact edge of a fish-holding front.

Distance rings: great-circle distances of 20/40/60/80 nautical miles from approximate town coordinates, not boat routes. A reported-distance card appears only for a verified source report less than 3 days old; older, future-dated or incompletely dated reports are omitted. It expires after 72 hours, independently of the map. Distance units stay as stated in the source.

Evidence and limits: 93% of Canada's 2017 fleet catch across all its fishing areas was in 15-18°C, but other research gives a broader 14-19°C niche. That does not mean a 93% chance of catching tuna. Catch-temperature evidence ↗ · Thermal niche ↗. NE Pacific research associates catches with SST fronts, but this simple gradient display is not that study's fitted catch model. Fronts study ↗

Action bar: actual local tuna catch reports within 14 days, counted once per boat/trip. Require 3 independent reports from 2 source outlets. Explicit Slow/Mixed/Good/Hot descriptions form a median category, not a probability. Promotions, forecasts and historical articles do not count. Insufficient evidence stays unrated.

Updates: visible all year. Each twice-daily site update checks for a new daily SST analysis and rebuilds both map layers when the analysis date changes. The real timestamp stays visible; data older than 3 days are labelled historical. A failed API check keeps the last real map with a warning. DFO rules and catch reports keep their own check dates. No automatic article scraping. These maps do not assess fish presence, clarity, depth, fuel, sea state, safe routes or legal access. Check marine forecasts and exact-area fishing rules before a trip.

Temperature map: satellite-derived NASA JPL MUR daily sea-surface temperature is sampled every 0.05° (~3-6 km). The hatched 15-18°C band is a research reference, not a fish detector.

Temperature breaks: for each ocean grid cell, compare the temperatures on either side east-west and north-south. Divide each difference by the distance between those neighbouring cells, correcting longitude distance for latitude. Combine the two rates as sqrt((east-west change)^2 + (north-south change)^2), in °C/km. A sharper colour means a stronger analysed temperature gradient. Land, missing neighbours and grid edges are masked, so a grey coastal patch does not always mean land. The colour scale is fixed at 0-0.12°C/km with higher values capped at the brightest colour for display only. There is no tuna-presence threshold or catch probability. Daily gap filling and coarse sampling can smooth, shift or miss fronts. This is an environmental clue, not the exact edge of a fish-holding front.

Distance rings: great-circle distances of 20/40/60/80 nautical miles from approximate town coordinates, not boat routes. A reported-distance card appears only for a verified source report less than 3 days old; older, future-dated or incompletely dated reports are omitted. It expires after 72 hours, independently of the map. Distance units stay as stated in the source.

Evidence and limits: 93% of Canada's 2017 fleet catch across all its fishing areas was in 15-18°C, but other research gives a broader 14-19°C niche. That does not mean a 93% chance of catching tuna. Catch-temperature evidence ↗ · Thermal niche ↗. NE Pacific research associates catches with SST fronts, but this simple gradient display is not that study's fitted catch model. Fronts study ↗

Action bar: actual local tuna catch reports within 14 days, counted once per boat/trip. Require 3 independent reports from 2 source outlets. Explicit Slow/Mixed/Good/Hot descriptions form a median category, not a probability. Promotions, forecasts and historical articles do not count. Insufficient evidence stays unrated.

Updates: visible all year. Each twice-daily site update checks for a new daily SST analysis and rebuilds both map layers when the analysis date changes. The real timestamp stays visible; data older than 3 days are labelled historical. A failed API check keeps the last real map with a warning. DFO rules and catch reports keep their own check dates. No automatic article scraping. These maps do not assess fish presence, clarity, depth, fuel, sea state, safe routes or legal access. Check marine forecasts and exact-area fishing rules before a trip.

Temperature map: satellite-derived NASA JPL MUR daily sea-surface temperature is sampled every 0.05° (~3-6 km). The hatched 15-18°C band is a research reference, not a fish detector.

Temperature breaks: for each ocean grid cell, compare the temperatures on either side east-west and north-south. Divide each difference by the distance between those neighbouring cells, correcting longitude distance for latitude. Combine the two rates as sqrt((east-west change)^2 + (north-south change)^2), in °C/km. A sharper colour means a stronger analysed temperature gradient. Land, missing neighbours and grid edges are masked, so a grey coastal patch does not always mean land. The colour scale is fixed at 0-0.12°C/km with higher values capped at the brightest colour for display only. There is no tuna-presence threshold or catch probability. Daily gap filling and coarse sampling can smooth, shift or miss fronts. This is an environmental clue, not the exact edge of a fish-holding front.

Distance rings: great-circle distances of 20/40/60/80 nautical miles from approximate town coordinates, not boat routes. A reported-distance card appears only for a verified source report less than 3 days old; older, future-dated or incompletely dated reports are omitted. It expires after 72 hours, independently of the map. Distance units stay as stated in the source.

Evidence and limits: 93% of Canada's 2017 fleet catch across all its fishing areas was in 15-18°C, but other research gives a broader 14-19°C niche. That does not mean a 93% chance of catching tuna. Catch-temperature evidence ↗ · Thermal niche ↗. NE Pacific research associates catches with SST fronts, but this simple gradient display is not that study's fitted catch model. Fronts study ↗

Action bar: actual local tuna catch reports within 14 days, counted once per boat/trip. Require 3 independent reports from 2 source outlets. Explicit Slow/Mixed/Good/Hot descriptions form a median category, not a probability. Promotions, forecasts and historical articles do not count. Insufficient evidence stays unrated.

Updates: visible all year. Each twice-daily site update checks for a new daily SST analysis and rebuilds both map layers when the analysis date changes. The real timestamp stays visible; data older than 3 days are labelled historical. A failed API check keeps the last real map with a warning. DFO rules and catch reports keep their own check dates. No automatic article scraping. These maps do not assess fish presence, clarity, depth, fuel, sea state, safe routes or legal access. Check marine forecasts and exact-area fishing rules before a trip.