I don't think so because their in the water.
Gain heat
Freshwater fish tend to gain water.
For what?It requires a heat gain for the water,but a heat loss for whatever the water is in contact with.
Sure, if one object loses heat, another will gain it.However, it might then be called heat gain.
heat loss
A temperature change requires as gain or loss of heat energy.
NO Heat Loss , No Heat gain
fish
No, fish can not sit out in the sun and gain energy, sorry
Newspaper and styrafoam.
Heat energy - yes. Temperature - no.
No.