i figured this would come up eventually as it related to a general principle in fish ecology. the principle is correct, although its application here is different (may not have time at the moment to get into all of it - but will try) - this case is an individual fish, and a rare one at that. it would likely have some impact on the other fish, but doubtful that it would be significant population-wise. the ecofish principle we are talking about refers to fishing down many large individuals, not a single one. that and this is also species specific...gars are much more gape-limited than other fishes of comparable size, so their impact on other populations and other fishes is different (can expound on those details later).
so yes, removing many large individuals would have an impact on the rest of the community, but taking into account this is just a single fish, and gator gars are uncommon-rare in much of their present range, the impact of the removal of this one fish would do little to the remaining fish community, let alone other gator gars (in terms of food and growth...this was likely a large female, so taking a large egg-producing member of the population out of the picture could have some impact).--
--solomon