saadia
you're right
this is from the food standards agency...
Do canned fish, such as tuna and salmon, count as oily fish?
Salmon, sardines, mackerel, trout and pilchards all count as oily fish when they're canned and when they're fresh. This is because the canning process doesn't significantly reduce the fat content of the fish.
Fresh tuna is an oily fish, high in fatty acids. But when it's canned, these fatty acids are reduced to levels similar to white fish. So, although canned tuna is a healthy choice for most people, it doesn't count as oily fish.
We should all eat at least two portions of fish a week, including one portion of oily fish. A portion is 140g. Girls and women who might have a baby one day, and women who are pregnant or breastfeeding, shouldn't eat more than two portions of oily fish a week. Other women, boys and men can eat up to four portions a week.
People can eat as much tinned tuna as they like, except women who are pregnant or are planning to get pregnant in the next year. These women should eat no more than four medium-size cans of tuna a week (with a drained weight of about 140g per can), or two fresh tuna steaks (weighing about 140g when cooked, or 170g raw).
you learn something new every day.