Celebrity Oxford chef Alex McKay reminds us of just how important our scaled friends are in the food chain

What sort of fish is it, daddy?” Last week my sons asked me this when I cooked a whiting.

Today we could be eating one of about 30 or reading about one of 32,700 living species (numbers according to fishbase). I grew up next to the sea in New Zealand. I fished whenever I could and my worry then was the men I saw catching fish and leaving it to rot.

They never took the fish, just kept it next to them on the pavement so that passing people could see how many these macho guys had caught. Size didn’t matter to these men; I once got a whack around the ears for sneaking a small one back into the water.

Still, I caught plenty of fish in those days over 30 years ago. On my last visit home two years ago I sat in the same spot and didn’t catch one. If we are to have fish in the future we have to educate and involve ourselves, we need to want it and we need to ask for it.

There are no or few fish that are always plentiful from all sources, so we need to know where the fish we buy is from.

A free way to find out which fish are sustainable is via mcsuk.org and msc.org – their lists and apps get updated, so you can be as current and informed as possible.

We can insist that supermarkets and fishmongers sell us sustainable fish by only buying fish that is certified sustainable and only buying it outside of its spawning season.

We need to eat a wider variety to create a market that sees equal opportunities for all fish.

Coley, pouting pollock and dabs are all fantastic fish, but because they are not familiar there is little or no market for them, yet the internet means that it has never been easier to find new recipes and ways to prepare new fish.

If every fish that is legally caught becomes marketable and we eat a wider range of fish generally, we can increase the demand for some and lower it for others to help even things out. Lesser known and more plentiful fish are generally cheaper too.

There is a lot to learn, so let’s start with a single sustainable idea that can improve our diets and feed the next generation better.

All nutritionists and even the culinary extremists with their diet diaries agree that we should eat more oily fish. Fish like herring qualify as “oily fish” because they are species that store oil in their flesh rather than having it concentrated in their liver as a “white fish” like cod does.

Oily fish are a good source of Omega 3 polyunsaturated fatty acids. Omega 3 is said to help with memory and heart health, lower cholesterol, also to help fight depression, stress, anxiety, ADHD, hyperactivity, bipolar disorder, schizophrenia and OCD. It can help you and your children’s concentration too.

This by itself is a great reward in these rattled times of constant multitasking. Oily fish include tuna and salmon. I’ll steer clear of those two, except to say that once tuna is canned it doesn’t count as oily because canning reduces tuna’s fats to levels similar to white fish.

Sardines and herrings are two fish that grow quickly, reproduce quickly, and count as oily whether they’re canned, fresh or frozen.

They are often sold whole, but if you don’t like eating whole fish, don’t worry; the fishmonger in the covered market sells filleted sardines and will scale and filet herrings. If enough of us ask for this at the supermarkets then surely more of them will do the filleting as well.

These delicious fish take a couple of minutes to fry or grill, do you immense good, are cheap and at the time of writing are considered sustainable.

Taking it further, more schools could make it policy to employ only caterers who put sustainable oily fish on their menus, to feed our children’s brains as well as their bodies while educating them on how to eat sustainably. The caterers could be asked to come and talk to kids about the fish, they could supply images and information to the schools that they take money from.

All of us can do something, and if all of us do, then maybe our children’s children can ask them “what sort of a fish is it? Otherwise the question will be: “What was a fish?”