First of all, to support the argument that the decline of fish populations in Tria is the result of overfishing rather than pollution, the author compares some regulations of the two marine sanctuaries which was established to protect certain marine mammals. However, the evidences are improper to support the argument since fish is of course not marine mammal. It is possible that the decline of fish populations in Tria means the growth of marine mammal populations who prey on fishes.
Secondly, the author assumes unfairly that all the conditions between Tria and Omni are entirely tantamount except the regulations. However, the argument provides no evidence establishing the assumptions. As a result, there is no point of reference that would make the suggested comparison meaningful. It is possible that although the regulations of the marine sanctuary, all of Tria's marine wildlife was exposed to pollution much more than Omni.
Thirdly, the author also assumes unfairly that people caught a great number of fishes because fishing was not banned. This is certainly not the case. Although fishing was not banned, people might have not caught fishes. To strengthen the argument, the author would need to provide clear evidence that people caught so much fished that it influenced to the decline of fish populations in Tria.
Finally, even assuming that the decline of fish populations in Tria is the result of overfishing, there is absolutely no evidence that adopting new regulations of the marine sanctuary can protect all of Tria's marine wildlife. There are various ways to protect all the marine wildlife. However, the author ignores other possibility that can protect all the marine wildlife.
In sum, the argument relies on certain doubtful assumptions that render it unconvincing as it stands. To strengthen this argument, the author needs to provide sufficient evidence and information that will eliminate all the above questions and doubts. Then, the argument can be...