**6. Conclusions**

*Natural History and Ecology of Mexico and Central America*

The structure of coral reef fish communities could be influenced by natural and anthropogenic sources. The climate change may affect small sedentary fish more than large species [71]. However, the former might allow faster adaptation to new environmental conditions [72]. Given the general deterioration of reefs, a lower abundance is

An examination of exploited fish stocks of the southern Mexico and the Mexican Caribbean suggests that the main fisheries are composed by transient species, whose distribution extends to the warm-temperate region of the East and South Eastern USA; on the south side, fish fauna share components of Caribbean species whose distribution range up to the Brazilian coast in many cases. The main components of the exploited stocks are species dwelling the shelf grounds, and a smaller component is based on coral reef dwelling species. The general perception is that overfishing is a major concern for many reef-fish populations, and this activity may be one of the most important activities contributing to degradation of coral reefs in the southern Gulf of Mexico [17] and the Mexican Caribbean [16]. In the reefs of Veracruz, around 50 out of the 550 reef-fish recorded, are often used for fisheries. Some of them are caught directly on the coral reefs using hooks and harpoons [80, 81].

An overview of the fisheries of the Gulf of México [82] allows to conclude that the fisheries of the south and north Gulf display rather independent trends, being the Gulf menhaden (*Brevoortia patronus*) on the northern Gulf, the species ruling this trend, and representing more than 90% of the whole catch. In the southern Gulf the whole catch is more stable over time than the one of the northern Gulf and the Gulf menhaden does not appear in catch records, whose volume ranges between 50,000 and 100,000 t in the northern Gulf. On both sides, at the north and south Gulf, mullets became more abundant over the recent years, which together with shrimp and crabs as scavengers, suggest a probable increase of debris, caused by the intensity of fisheries trawling of the shrimp grounds. Other important exploited stocks deserving to be mentioned are the Spanish mackerel (*Scomberomorus maculatus*) and the King mackerel (*Scomberomorus cavalla*), two migratory species up in the food web as predators, running along the coasts of the state of Veracruz, with catch volumes of +5200 and 2300 t per year respectively. These

The fish species associated with reef and rocky areas (Gulf of Mexico and Mexican Caribbean) are usually reported in a group called "escama (scale fish)". They include groupers (e.g. *Epinephelus morio*), snappers (e.g. *Lutjanus jocu*), porgies (e.g. *Calamus bajonado*), grunts (e.g. *Haemulon plumierii*), hogfish (*Lachnolaimus* 

*maximus*), and tilefish (*Lopholatilus chamaeleonticeps*) among others [83].

two species also are important for fisheries on the north Gulf.

expected, not only of large carnivores but also of small specialist fishes [50]. The fishing pressure over fishes in coral reefs of the Gulf of Mexico and the Mexican Caribbean has produced changes in the richness and abundance of fishes [16, 50, 73]. For example, the fishing of groupers in the Mexican Caribbean caused the disappearance of the aggregation of Nassau grouper off Mahahual [74]. On the other hand, the scarcity of commercial fish species (e.g. snappers and groupers), become the parrotfish as a target group of spear-gun fishing as a result of the increasing of tourism along this area [73]. In the southern Mexican Caribbean there are a decreasing of coral reef fishes that is more evident in the large piscivores [50]. The anthropogenic disturbances, the tourism and river discharges are related to high nutrient levels on reef systems [21, 75], and could be linked to observed seagrass and hard coral cover loss over the last decades as in the Gulf of Mexico [21, 76] as in the Mexican Caribbean [77, 78]. The sediments and nutrients in coral reefs increase the turbidity and modify the richness and abundance of herbivorous fishes [66, 79].

**150**

**5. The fisheries**

Species diversity of the Gulf of Mexico despite it does not show any evidence of being limiting for the Caribbean species, it somehow constrains the entrance to all typical Caribbean forms and in many zoological groups there are some species that are not found inside the Gulf and is known that some of these penetrate a far as the Campeche Bank reefs, or as occurs in some cases, they display very low abundances, like the Red grouper (*E. morio*), the Nassau grouper (*Epinephelus striatus*), the Gag (*Mycteroperca microlepis*). By contrast, there are a few fish species which are endemic to the Gulf of Mexico, like the Black snook (*Centropomus poeyi*), and Jarocho goby (*Elacatinus jarocho*)*,* to just mention a few. After these examples, we can state that the Gulf of México contains some characteristics restricting the penetration of some Caribbean forms. It is pertinent to mention that in this chapter, mixohaline species associated to the brackish-waters are not considered.

In regard to the exploited fish stocks, two explanations are given respecting to significant changes of their biomasses, one is attributable to fishing intensity, and the other is to climatic variability. We consider that under certain circumstances, both factors may be responsible for these changes, especially if we look into particular fish stocks. Environmental variability is responsible of sudden changes in the biomass of short-lived species like sardine and related life forms, enhancing sudden increase or dramatic reductions [86] affecting productivity and the carrying capacity of the habitat. In contrast, long-lived stocks usually are able to support the effects of north winds occurring in winter, excepting those cases causing mass mortalities, and their biomasses are more related to their life spans and carrying capacity. The catch in the south Gulf of Mexico is estimated in 0.11 t/km2 [87], and it was found a positive correlation of one year delay between yield and Chlorophyll *a* concentration.

Coral reefs of the Mexican Caribbean as well as those of the south of Gulf of Mexico have drastically changed over the last decades [41]. Recent studies showed an increase of macroalgae coverage and a decrease of coral cover [88] impacting coralline assemblages like herbivorous fish [73] by the lost of habitats and fishing pressure [16, 84]. The effects of fishing were detected in individual fish size and there were more evident on the unprotected reefs [16], where the commercially important species belonging to Serranidae, Lutjanidae, Carangidae, and Sphyraenidae were recorded by these authors in small quantities.
