auchenoglanidines, ariids, austroglanidids and cranoglanidids) than to pangasiids (Mo; De Pinna, 1998; Diogo et al., 2002a; Diogo, 2003ab, 2004), this feature was seemingly independently acquired in these two groups.
Two common ariids in Paranagua Bay are nocturnal in shallow waters (Oliveira Neto et al., 2004), although by day may be caught in large numbers in deeper waters (Schwarz Jr., 2005).
In the case of sciaenids and ariids, the fish remain inactive and/or grouped during the day outside the tidal channels, probably in deeper areas.
The most external zone, the lagoons and estuaries where the tide prevents stagnation and excessive increases in water temperature, is an important shelter for mollusk and crustacean larvae, and especially for the fry of fish (more than 400 species), mainly clupeids (Brevoortia), engraulids (Anchoa), sciaenids (Bairdiella and Cynoscion), ariids (Arius), centropomids (Centropomus), and others.
Leiognathids were the most abundant group (about 80% of 5,997 fish trawled), followed distantly by pomadasyids (9.7%), ariids (2.5%), mullids (1.7%), and 18 other groups (about 6% combined).