Ellianna cooking 40 herrings with 40 oz of fat each gives her 40*40 = <<40*40=1600>>1600 oz of fat.
If Ellianna also cooked 40 eels with 20 oz of fat each, she got 40*20 = <<40*20=800>>800 0z of fat.
All the herrings and eels together have a total fat content of 1600+800 = <<1600+800=2400>>2400 oz of fat.
A pike, with 10 more oz of fat than an eel, has 10+20 = <<10+20=30>>30 oz of fat
Cooking 40 pikes gives 40*30= <<40*30=1200>>1200 oz of fat.
Since Ellianna cooked all the fish, she had 1200+2400 = <<1200+2400=3600>>3600 oz of fat in her serving.
#### 3600