There’s been a good number of days this summer where the temperature has reached 30 degrees. During the daylight hours, either side of midday, on such sweltering days, you feel like seeking the coolest place and just hunkering down until the evening. Fish are no different. As a general rule, they become inactive during those hours from about 10am to 5pm or 6 pm.

I’m bemused when, on a clear mid-summer morning, at about 8am or 9 am, I see boat anglers heading to the launching ramps. By the time they’ve launched and made their way to the fishing spot, it’s probably half past nine or 10am, just as the day’s heat is intensifying. If it’s a cloudless sky and a ‘dog day’ in prospect, they’re hours late. Instead of heading out on the boat at 8:30am, they should be returning from an early morning fishing expedition.

The term ‘dog days’ of summer attached to the blazing sun and heat in mid-summer relates to the heavens. The expression in the northern hemisphere refers to the period from 3 July to 11 August when the very bright ‘Dog Star’ Sirius is highly visible at dawn as the sun is about to rise.

The ancient Greeks felt that the dual combination of the star and the rising sun caused the extreme heat during mid-summer.

I guess the term associated with sweltering heat in the summer was brought down to the southern hemisphere by the early migrants.

Perhaps, we need to take a lesson from the canines in that dogs during hot daylight hours will seek the cool, invariably lying about in the shade dozing all day and will only become active in the evening.

Fishing early morning or late evening and into the night is the solution for the ‘dog day’ doldrums. Besides, fish such as snapper generally shun the bright light of the mid-summer sun, especially in shallower water.

The same rule of thumb applies with trout fishing. Trout are most active within the same temperature range, give or take a degree or two. When water temperatures in mid-summer get above 20 degrees, trout get sluggish with the water’s lower oxygen levels. Insect activity and, therefore, trout feeding activity generally taper off.

The optimum water temperature for trout is 14 degrees Celsius with a comfort range of 10 degrees to 18 or 19 degrees. Below 10 degrees, as in winter, trout metabolism slows down, making the fish sluggish, requiring less food. Above 20 degrees, lower dissolved oxygen levels slow trout activity. Again, getting out early pays off.

As the heat of the day disappears with evening, the water cools. Hence fishing in the evening and at dusk can be productive. Fishing after nightfall, i.e. in the dark can be excellent between hot summer days.

At the same time, focus your fishing on stretches of the river that may have welcome shade for trout from willows. Some pools have cool underwater springs welling up and in mid-summer. As water temperatures climb, trout will seek these cold water spots. Sometimes, small tributary streams with cooler water enter the parent river. I know of two such feeder streams in the Tukituki River in Hawke’s Bay and both are a magnet for trout seeking relief from the warm mid-summer water. By the same logic, rapidly moving water holds more oxygen than slow pools. It pays to fish the sections of the river or stream that contain the most oxygen, such as the faster water in rapids, bubbling pocket boulder-studded stretches and riffles. Avoid fishing still water with slow-moving water such as found in most large pools.

The water depth makes little to no difference. The most oxygenated water in the stream may be only inches deep, such as in riffles.

There are exceptions, such as land-based terrestrial insects, such as cicadas, falling into the water, and trout just love those big juicy mouthfuls. After all, a cicada or two in protein is the equivalent of hundreds of tiny mayflies.

But water temperature still is a major factor in the trout’s activity. Mornings may be good in cicada season, but the following sweltering heat in the afternoon will drive the trout to cease feeding. Therefore, timing becomes paramount in navigating the ‘dog days’ of summer, ensuring anglers align their efforts with favourable periods for a successful catch.

Words and image by Tony Orman