Both stratics and uoguide have an incredible amount of information on the new booster pack where a lot of testers slept too little to document. In fact, summer dragonfish is one of the first fishes we caught since it was on an obvious Dungeon which is figured out using Crysta logic: name vs dungeon (Destard). I encourage everyone to check those pages about the new booster, stratics has full info (credit goes to Petra) currently where uoguide is missing some.
Some advice:
For the fishers: you dont need much pvm skill to fish on Destard (or any other dungeon, including Twisted Weald) if you can hide from, lure away or kill the monsters around the fishing spots. I can say that the chance to catch one is more or less the same as the chance to catch a big fish. Using baits is always a wise thing to do while gathering specific baits requires some time (from professional fisher quest). Using a bait does not mean that your chance of catching the fish becomes 100% but it greatly improves your chances.
For the cooks: Each pie has different minimum skill requirement, eg. the summer dragonfish pie requires 68.0 cooking skill which means you have about 64% chance to bake one with gm skill. You wont have much trouble baking them with talisman giving a bonus on cooking skill. On all fish pies, you need 1 dough, 1 fruit/vegetable and 1 of the three newly introduced ingredients which can be bought from the tavernkeepers on the sea market. The only rare ingredient is the fish itself. We have yet to discover any difference on the effect of eating exceptionally baked pies but it doesnt mean there is none.