No abstract

Background. The leopard grouper, Mycteroperca rosacea (Streets, 1877), is endemic to northwestern Mexico and has high commercial value. Although facts of its basic biology are known, information on its trophic ecology, in particular, is scarce. The objective of the presently reported study was to characterize the feeding habits of M. rosacea through the analysis of stomach contents, and to determine possible variations linked to sex (male or female), size (small, medium, or large), or season (spring, summer, autumn, or winter), in order to understand the trophic role that this species plays in the ecosystem where it is found. Materials and methods. Fish were captured monthly, from March 2014 to May 2015 by spearfishing in Santa Rosalía, BCS, Mexico. Percentages by the number, by weight, and frequency of appearance of each food category, the index of relative importance (%IRI), and prey-specific index of relative importance (%PSIRI) were used to determine the importance of each prey item in the leopard grouper diet. Diet breadth was calculated using Levin's index. Possible differences in the diet by sex, size, or season were identified through a multivariate PERMANOVA analysis. Results. A total of 341 leopard grouper specimens were collected, 309 of which had stomachs containing food. A total of 28 prey species were identified. According to the %IRI, the contribution to the diet of the coastal pelagic prey Nyctiphanes simplex and Sardinops sagax (Jenyns, 1842) was 87%, whereas according to the %PSIRI the contribution to the diet of those two prey species was 57%, in addition to several demersal prey species. A PERMANOVA analysis indicated that there were significant differences in the diet of leopard grouper by sex, size, and season, but the interactions sex-size, sex-season, size-season, and sex-size-season, were not significant. Conclusions. Mycteroperca rosacea was identified as a carnivorous predator with narrow trophic width, with significant differences in diet according to the sex, size, season, and size-sex interactions, which could be the result of different energetic requirements, hunting abilities, and food availability. The %PSIRI turned out to be the most adequate index to determine the feeding habits of fish, as it provides a better mean value to determine the most important prey.

No abstract

The concentrations of essential (Cu, Zn) and toxic (Cd, Pb) elements were quantified in the muscle of leopard groupers, Mycteroperca rosacea, in a mining district in the Gulf of California. Metal concentrations were analyzed by size, sex, maturity, season, year, and a risk factor for human consumption. Results indicated elevated levels of essential elements (Cu: 11±34.3 μg/g, Zn: 377±1390 μg/g), up to 10 times higher than concentrations of toxic elements (Cd: 0.06±0.1 μg/g, Pb: 0.98±1.5 μg/g). Cadmium was within permissible limit stated by Mexican norm (0.5 μg/g), but lead bordering its limit (1.0 μg/g). Heavy metal concentrations were comparable between males and females. Metal variations were not significantly correlated to the sex, maturity, season, or year (p>0.05). The evaluation of benefits (Daily Mineral Intake) and risks (Target Hazard Quotients) to health indicated that these fish did not represent adverse effects to the consumer, within worldwide limits, but the nutritional benefits are high.

The Pacific porgy Calamus brachysomus (Lockington, 1880) is exploited for local consumption and commerce in Baja California Sur (BCS). Monthly samples to study its reproductive biology were obtained from the artisanal fishery operating in Santa Rosalía, BCS, Mexico, from July 2015 to July 2016. A total of 265 specimens were analyzed, including 147 females and 118 males. The sexual proportion (1.24F:1M) did not differ from the expected 1:1 proportion (P = 0.08). There were no significant differences between sexes in total length (P = 0.94). Variations in the hepatosomatic index and condition factor indicated that food constituted the main energy source during reproduction, with possible additional use of endogenous reserves originating in the liver during spawning. The gonads histological analysis indicated an asynchronous ovarian development and batch spawning strategy. There were spawning capable females during 11 of the 13 sampled months; the exceptions were February and September, coinciding with minimum and maximum sea surface temperature (SST) values. These results, along with the gonadosomatic index variations, allowed us to conclude that C. brachysomus reproduces over a large part of the year with an activity peak from May to July, in an SST interval of 21 to 28ºC.

The spotted rose snapper, Lutjanus guttatus (Steindachner, 1869), is an important resource for the coastal fisheries of the Gulf of California, mainly due to its high commercial value. Despite this, there are no management measures for this species, owing in part to a lack of information on its basic biology and its trophic ecology in the area. In this context, the presently reported study had as objective to describe the feeding habits of L. guttatus through stomach content analyses, as well as to describe possible changes linked to sex, size, and season. Specimens were caught monthly from June 2016 to September 2017 with gillnets in Santa Rosalía, BCS, Mexico. The abundance, weight, and frequency of occurrence of each prey were assessed, and these parameters were integrated into the index of relative importance (%IRI) to determine the importance of each prey item in the L. guttatus diet. The Levin’s index was used to assess the trophic niche width of the species, the feeding strategy was evaluated using Costello’s graphic method and the trophic level was calculated. Finally, to establish whether there were significant differences in the diet by sex, size, or season a PERMANOVA test was used with a 95% confidence level. A total of 202 L. guttatus stomachs were analyzed, 191 of which contained food. A total of 26 prey items were identified. According to the %IRI, the most important prey were the teleost fishes Harengula thrissina (Jordan et Gilbert, 1882) (45.7%) and Sardinops sagax (Jenyns, 1842) (34.8%), the euphausiid Nyctiphanes simplex (13.4%), and the crustacean Penaeus spp. (5.6%). The PERMANOVA analysis resulted in significant differences between the analyzed categories; however, there were no significant differences in the interactions among the categories. According to Levin’s index, L. guttatus had a narrow trophic width, with changes in the main prey consumed by the different categories. According to our results, L. guttatus can be considered a benthopelagic opportunistic carnivorous predator with a narrow trophic niche, presenting mostly quantitative variations in its diet according to sex, size, and season. Its trophic plasticity allows it to take advantage of the most available and abundant food resources.

No abstract

The concentrations of essential (Cu, Zn) and toxic (Cd, Pb) elements were quanti ed in the muscle of leopard groupers, Mycteroperca rosacea, in a mining district in the Gulf of California. Metal concentrations were analyzed by size, sex, maturity, season, year, and a risk factor for human consumption. Results indicated elevated levels of essential elements (Cu: 11±34.3 μg/g, Zn: 377±1390 μg/g), up to 10 times higher than concentrations of toxic elements (Cd: 0.06±0.1 μg/g, Pb: 0.98±1.5 μg/g). Cadmium was within permissible limit stated by Mexican norm (0.5 μg/g), but lead bordering its limit (1.0 μg/g). Heavy metal concentrations were comparable between males and females. Metal variations were not signi cantly correlated to the sex, maturity, season, or year (p>0.05). The evaluation of bene ts (Daily Mineral Intake) and risks (Target Hazard Quotients) to health indicated that these sh did not represent adverse effects to the consumer, within worldwide limits, but the nutritional bene ts are high.