The change in the mean trophic level of fish assemblages can be used as an indicator of fishing pressure. To gain a more detailed understanding of changes in trophic level, trophic spectra can be derived using a 3-point moving average technique. The mean trophic level was used to determine differences between reef fish assemblages inside and outside fish protected areas (FPAs) around Bonaire, Dutch Caribbean. Additionally, mean trophic levels of reefs spanning the entire Caribbean were calculated to enable comparison based on their level of degradation by anthropogenic disturbances. No difference was seen between the mean trophic level of sites inside and outside the FPAs, possibly due to the fact that the FPAs have only been in place for 4 years. Differences in mean trophic levels across the Caribbean were significant but did not correspond to estimated reef health, implying that mean trophic level may not be a good indicator of reef health. Reef fish assemblages seem to be affected by a variety of factors, not simply fishing pressure or reef health.
The ecology of common snook Centropomus undecimalis in Amatique Bay, a tropical estuary in eastern Guatemala, was investigated and life-history traits were used to conduct a meta-analysis of the species from Florida to Brazil. The reproduction cycle of C. undecimalis in Amatique was strongly related to the precipitation cycle, with a lag of 2months. Spawning occurred from April to November with a peak spawning after the onset of the summer rains. Protandric sex reversal occurred early in the dry season (December) before somatic recovery from spawning. The growth cycle preceded that of body condition by c. 1month, and was out of phase with the reproductive cycle. Growth was fast, as many individuals reached >70% of the maximum observed total length (LT, 102cm) after 3years. Sex transition occurred within a relatively narrow LT range (70–79cm), but over a wide range of ages, indicating plasticity in this respect. The meta-analysis indicated a latitudinal-temperature gradient in life-history traits, as well as different seasonal patterns relative to temperature and hydrographical cycles. Centropomus undecimalis from cooler winter waters (e.g. Florida) reach larger maximum LT and LT at sex change, as well as greater gonado-somatic indices and longer life spans. Further, increased fishing mortality results in younger age at sex reversal and male predominance in the populations compared. Recognition of large-scale biogeographic patterns in this important, but little studied, fish species helps in the formulation of management advice in other areas of its occurrence.