The hybridization and potential hybridization of NJ fishes

Hybridization is a lot more common than people realize, specifically in fish due to their indiscriminate breeding practices. A random egg floating in the water can fertilize with a random sperm, if the timing is right, and create a hybrid offspring. Hybrid offspring are usually not viable, and thus only serve as unique one time occurrences, but due to a phenomenon called hybrid vigor invasive hybrids can sometimes outcompete native fishes. The most common (or possibly just most obvious) hybridization is in sunfishes, and in fact already documented in the Northeast are 6 hybrid sunfish species:
- Pumpkinseed x Green (Lepomis gibbosus x cyanellus)
- Greengill (Lepomis macrochirus x cyanellus)
- Pumpkinseed x Bluegill (Lepomis gibbosus x macrochirus)
- Redbreast x Bluegill (Lepomis auritus x macrochirus)
- White x Black Crappie (Pomoxis annularis x nigromaculatus)
- Pumpkinseed x Warmouth (Lepomis gibbosus x gulosus)

However, other families of fish also hybridize, and also present in NJ are:
- Tiger Trout (Salmo trutta x  Salvelinus fontinalus)
- White x Striped Bass (Morone chrysops x saxatilis)
- American x Chain Pickerel (Esox americanus x niger)
- Pikerel (Esox lucius x niger)

Hybrids usually have intermediate features of their parents except in rare cases, meaning that a hybrid will on average be in-between the parents in every category (ray counts, length, width, etc.). They also tend to have "hybrid vigor", or above their parents' fitness, which can present a real problem for native fish which end up hybridizing with non-natives, as they are outcompeted by their (often infertile) offspring.