Length-weight relationships of 33 cryptic reef fishes from the southwestern Gulf of California were estimated. The most common families were Gobiidae (seven species), Labrisomidae (four), Pomacentridae (three), and Tripterygiidae (three). These are the first length-weight parameters reported for 32 of these species. Specimens were sampled during a comparative ecological study of community structure of fish assemblages associated with coral heads, rocky walls, and artificial reefs in Bahı´a de La Paz, Baja California Sur. The b values varied between 2.63 and 3.61. New maximum length records for five of the species were established in the study.

The inshore lizardfish, Synodus foetens, is one of the most common coastal demersal predators on the continental shelf of the Gulf of Mexico (GOM), but the biology and feeding ecology of this species is virtually unknown. Between November 2001 and January 2003 (10 collections), 603 individuals of S. foetens ranging from 112 to 420 mm standard length (SL) and 13 to 630 g (wet weight) were collected from the continental shelf of Alvarado, Veracruz, Mexico. About 60% of the individuals had empty stomachs with the stomach fullness of the remaining individuals being distributed as follows: 5% full (24.8%), 50-75% full (13.5%), and completely full (1.7%). The mean (± SD) wet weight of stomach contents was 12.1 ± 10.8 g during the rainy season, and 19.0 ± 13.0 g during the nortes season. Seventeen prey items were identified, with the majority thereof being fish. The most important prey items were Upeneus parvus, Loligo pealei, Engyophrys senta, Trachurus lathami, and Anchoa hepsetus. Seasonal changes in the diet were observed, with U. parvus and L. pealei being the most important prey during the nortes season, whereas E. senta and L. pealei were the main items during the rainy season. Prey size selection was evident among size classes of S. foetens, although no trophic overlap was observed among size classes (C ik £ 0.004). High trophic level values were determined for all size classes by season (rainy season ¼ 4.67, nortes season ¼ 4.84), and indicated this species belongs to the piscivorous trophic guild that preys upon both demersal and pelagic species.

The record of free and healthy Mediterranean gilt-head seabream Sparus aurata Linnaeus, 1758 in waters of the Gulf of California, México is documented for the first time. Consequences of this introduction are briefly outlined.

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Length-weight relationships (LWR) were estimated for 34 fish species belonging to 25 genera and 17 families, specimens were collected near the mouth of the Rı´o Verde, Oaxaca, Mexico. All r 2 values are statistically significant (P > 0.0001). The values of ÔbÕ ranged from 2.55 and 3.3, within the usual range (2.5-3.5). This study provides the first LWR references for six species, and new maximum length records for eight species.