Jim,
I have never bonked hoop-netting although I do not really hoop net very often. I do run many marathons, compete in triathlons as well as century bike rides (100 mile +) each year and have bonked during those activities. High endurance activities cause muscle fatigue and your body to use up all its energy.... hitting a wall (yes there is a much more scientific explanation I won't go into). Basically the energy to power your muscles come from ATP formed from metabolism of fats and carbohydrates. Your body prefers to use carbohydrates which are stored as glucose in your blood, muscles and liver. Unfortunately your stores of glycogen are limited. Most endurance athletes are able to store somewhere around 2000 to 2200 calories worth, good for about 20 miles if you don't restore while running you hit a wall. This is where energy drinks and eating high carbohydrates come in. Endurance athletes also have high carbohydrate diets low carb diets don't work, you will hit a wall.
It is possible that with loading your kayak, paddling and then the workout of pulling and dropping and your current physical shape (what ever it is good or bad) you are burning through your stored energy. Eating more carbs in your diet will help. Also eating while you are on the kayak as well as a sports drink.
Gatorade is high in carbs and sugar I like Gatorade but also enjoy Nuun it is conveinient because you just put a tablet in water and you are good to go. So you can drink water but if you are feeling low on energy pop one of these in
http://www.nuun.com/
Gu energy works great for endurance events but who wants to suck this crap down when fishing. Eat energy bars, I like cliff bars and luna bars. Luna bars are marketed towards women athletes but they taste much better than others. Try the Lemon Bar!
When you work out you also sweat out your salt which your body depends on, without the salts you are likely to cramp. Eat trail mix, salted peanuts, sunflower seeds, trailmix bars
Eat a good high carb meal before going out Pasta, potatoes, pancakes, breads
Recover with protein. Chocolate milk, fresh fish, fresh lobster with carbs! rice, pasta, sourdough bread