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We present the length-weight relationships (LWRs) in 20 cryptobenthic reef fish species in the Gulf of California (Mexico). Nine of these species had no LWR records yet. However, the other species had LWRs based on in-formalin specimens collected more than 20 years ago. This conservation method has likely affected LWRs parameters. Our study showed higher estimations of the parameter a obtained on fresh specimens than in-formalin individuals. On the other hand, parameter b was not affected. Therefore, the biomass estimates using previous LWRs were strongly underestimated. Ergo, the similitude in parameter b between the two conservation methods highlights that the shape of the LWRs is conserved and did not change over the last 20 years. Finally, we compared the LWRs of shared species in the region’s two main types of shallow reefs, i.e., coral and rocky reefs. We found that the body fitness was not affected by reefs type, which means that both habitats seem to offer similar living conditions for shared species.

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.

Background. The sailfish Istiophorus platypterus is a viviparous billfish species, it is caught by trolling in the sports fishery in Mexico. However, to date, there has been no reproductive biology studies of sailfish in Acapulco Bay, although the reproductive aspects of any species represent essential information for the design of management plans. Goals. Estimate the spawning frequency and batch fecundity to quantify reproductive characteristics of sailfish in waters off Acapulco, Bay. Methods. During the period 2008–2019, a total of 581 fish were sampled. Macroscopy analysis and quantitative histology was used to describe reproductive characteristics of the sailfish gonads. Results. 55.8% of the organisms analyzed were males, the remaining 44.2% were females, the sex ratio (1.26 M: 1 H) was different from the expected theoretical ratio (X2 = 7.53). The ovaries of 155 females were classified into five ovarian development phases based on histological analysis of the most advanced group of oocytes. Sailfish are multiple spawners with asynchronous oocyte development. Batch fecundity for 14 females with the presence of hydrated oocytes but without postovulatory follicles ranged 0.330 to 2.092 × 106 eggs with an average of 1.07 × 106 eggs. Gonadosomatic indices (GSI) indicated that sailfish have a reproductive period with peaks in August and October (mean monthly GSI= 4.3% and 5.4%). Conclusions. Population sailfish in Acapulco Bay is composed of males and females in similar proportions, with a gonadal development by groups that can be described in five development phases, a reproductive maximum during the warm months of the year and a relatively high fecundity.

Null purse seine sets (those in which the catch is zero) are common in every tuna fishery in the world. Current evidence suggests that different environmental factors can influence the occurrence of null sets. In this study, we used a long-term (2003–2015) database from the tuna purse seine fishery in the eastern Pacific Ocean to analyze the temporal and spatial variability of the occurrence of 1º × 1º quadrants where the retained tuna catch was zero (“null cells”). We fitted a logistic generalized additive model to predict the occurrence of null cells as a function of environmental and operational covariates. Results of the modeling process suggested that high probabilities of null cell occurrence exist mainly in 2 environmentally different zones: the entrance to the Gulf of California, Mexico, and off the coast of Central America. The final statistical model suggested that operational variables (number of sets, type of fishing indicator) are more important to null cell occurrence than environmental factors (sea surface temperature, chlorophyll concentration, sea level anomaly, and El Niño events).

The leopard grouper Mycteroperca rosacea is endemic to northwestern Mexico. It has been classified as vulnerable by the IUCN since 2008. M. rosacea has high commercial value and is caught yearround in Baja California Sur (BCS). Biological information on this species, especially in its natural environment, is scarce, and the objective of this study was to analyze its reproductive biology in Santa Rosalia, BCS. A total of 345 specimens were collected from March 2014 to May 2015. The sex ratio was 2.0: 1.0 (females: males, P < 0.05). Population size at first maturity (L 50 ) was estimated at 40.77 cm TL; 37.31 cm TL for males and 42.44 cm TL for females. Gonadic development was synchronous by group, with a reproductive period occurring from March to May in 2014 and 2015 (at 20-23oC). The gonadosomatic index achieved maximum values in May 2014 and March 2015, as did the highest frequencies of mature and spawning individuals, indicating that there was a clear seasonal pattern of reproduction, and a negative correlation with temperature for both sexes. The hepatosomatic index and the condition index indicated that M. rosacea is not a species that requires storing of energy for reproductive events, as it seems to have food available year-round. Normal 0 21 false false false ES X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Tabla normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; line-height:115%; mso-pagination:widow-orphan; font-size:12.0pt; mso-bidi-font-size:11.0pt; font-family:"Times New Roman","serif"; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi; mso-ansi-language:ES; mso-fareast-language:EN-US;}

Five leopard grouper Mycteroperca rosacea specimens were captured in the Gulf of California, two of which presented a rare orange pigmentation on both sides of the body. The remaining individuals presented changes to the normal pigmentation pattern on the left or right flanks. The possible causes of these phenomena are discussed.

Feeding habits determine many aspects of living organisms, where it lives, the time of day that it is active, energy flow, biomass consumed and intra- and interspecific interactions, it which provides information to make predictions about the effects of fisheries on predator-prey relationships. Accurate predictions require a thorough understanding of predator diets and prey selection. In this study, specimens of the crevalle jack Caranx caninus were obtained between October 2012 and October 2014 in the SE Gulf of California, Mexico, in order to determine its feeding habits and prey selection. A total of 238 specimens were obtained, of which 94 (39.5%) had stomachs containing food and 144 (60.5%) had empty stomachs. A total of 10 prey items were identified, corresponding to seven families that included fishes, crustaceans and cephalopods. According to the Index of Relative Importance (IRI) the most important prey were Anchoa spp. (IRI = 91.2%), Engraulis mordax (IRI = 1.8%), and fish from the Clupeidae family (IRI = 1.0%). The crevalle jack’s diet did not change with the season (warm or cold). The crevalle jack was considered a tertiary predator (trophic level = 4.3) that tends to feed on a reduced number of prey, characterizing it as a specialist and selective predator of engraulid fishes (Levin’s index, Bi = 0.08; E = 0.6).

espanolEl estudio de los habitos alimentarios de la barracuda mexicana, "Sphyraena ensis" Jordan y Gilbert, 1882, es importante para conocer los aspectos relevantes de su ecologia trofica (presas consumidas, amplitud de dieta, nivel trofico y flujos de energia), ya que brindan informacion valiosa sobre la dinamica de las comunidades marinas. En este contexto, el objetivo del presente trabajo fue determinar los habitos alimentarios de la barracuda mexicana, S. ensis, asi como las variaciones troficas con respecto a sexo (machos, hembras), tallas (individuos pequenos, medianos y grandes) y estacionalidad (lluvias y secas). Se obtuvieron muestras mensuales durante el periodo de febrero de 2014 a enero de 2015 en la region de San Blas, Nayarit, Mexico. En total se capturaron 308 organismos, con tallas de entre 30.6 y 58.7 cm de longitud total y pesos de entre 405 y 836 g. De los estomagos analizados, 264 (86%) contenian alimentos y 44 (14%) estaban vacios. El espectro trofico de la barracuda mexicana se conformo de 13 tipos de presa, agrupadas en 11 familias, 12 generos y 9 especies. De acuerdo con el indice de importancia relativa, las presas mas importantes fueron los peces, particularmente Sardinops spp. (40.36%), Hemiramphus saltator (40.24%), Opisthopterus dovii (10.83%), Anchoa spp. (4.17%) y Mugil cephalus (3.05%). Con base en los resultados obtenidos, la barracuda mexicana puede categorizarse como un depredador ictiofago oportunista de la zona epipelagica costera que se alimenta, principalmente, de especies de peces que forman densos cardumenes. Su espectro trofico no presento variaciones significativas por sexo y talla, pero el consumo de las presas mas importantes vario significativamente por estacion. EnglishUnderstanding the feeding habits of the Mexican barracuda, "Sphyraena ensis" Jordan and Gilbert, 1882, is important to elucidate relevant aspects of its trophic ecology (prey intake, diet breadth, trophic level, and energy flows), which in general provide valuable information on the dynamics of marine communities. Therefore, the purpose of this work was to assess the dietary habits of the Mexican barracuda, S. ensis, and to determine dietary variations by sex (males, females), size (small, medium, and large individuals), and season (rainy and dry). Monthly samples were obtained from February 2014 to January 2015 in the San Blas region, Nayarit, Mexico. A total of 308 specimens were captured. Individuals measured between 30.6 and 58.7 cm total length and weighed between 405 and 836 g. Of the analyzed stomachs, 264 (86%) contained food and 44 (14%) were empty. The diet of the Mexican barracuda comprised 13 prey items from 11 families, 12 genera, and 9 species. According to the index of relative importance, the most important prey were fishes, particularly Sardinops spp. (40.36%), Hemiramphus saltator (40.24%), Opisthopterus dovii (10.83%), Anchoa spp. (4.17%), and Mugil cephalus (3.05%). We conclude that the Mexican barracuda can be categorized as an opportunistic ichthyophagous predator in coastal epipelagic zones that feeds mainly on schooling fish species. The trophic spectrum did not vary significantly by sex or size, but the consumption of preferred prey varied significantly by season.

The parameters of length‐weight relationship (LWR) are presented for seven species of catfish from the southeastern Gulf of California. Samples were obtained every three months, in Bahia de Matanchen (using bottom trawl nets consistent of 72 hauls, with mesh sizes of 3.2 cm in the wings and 2.54 cm in the cod‐end) from February to November, 2016 and in the San Blas estuarine system (using gill nets consistent of 32 hauls, with mesh sizes of 5 cm) from August, 2015 to May, 2016 respectively. The allometric coefficient (b) of LWR varied from 2.797 for the Cominate Sea Catfish (Occidentarius platypogon (Gunther, 1864)) to 3.373 for the Tete Sea Catfish (Ariopsis gilberti (Jordan & Williams, 1895)). Four species reached new records on maximum total length (Tete Sea Catfish, A. gilberti; Widehead Sea Catfish, A. guatemalensis (Gunther, 1864); Conguito Sea Catfish, Cathorops liropus (Bristol, 1897); and Curator Sea Catfish, C. raredonae Marceniuk, Betancur‐R, & Acero, 2009). For six of these species this accounts for the first report on estimations of LWR parameters.

The Galapagos sea lion, Zalophus wollebaeki (GSL), is endemic to the Galapagos Archipelago and is considered endangered by the International Union for Conservation of Nature (IUCN). Population status has undergone a drastic decline over the last four decades, partially due to oceanographic anomalies like El Nino-Southern Oscillation (ENSO) events. To assess the impact of the strong 2015–2016 ENSO on GSLs, their diet diversity, trophic niche breadth, and trophic level (TL) from 2014 to 2016, were evaluated through scat analysis (N = 360; 120 samples per year) in San Cristobal Island. The overall trophic spectrum comprised 72 species, mainly fish species and one squid species; the most important prey (IIMP) during the study period were Opisthonema berlangai (11.51%), Vinciguerria lucetia (8.82%), and Symphurus spp. (8.17%). There were no significant interannual differences (F=2.15, p=0.104) in the abundance of prey from six different habitats; however, GSLs consumed a greater abundance (47%) of benthic prey in 2015. The PERMANOVA analysis detected interannual dietary differences (F=11.9, p=0.001) and the NMDS test indicated that, GSL consumed a greater proportion of benthic prey in 2015. The GSL can be classified as a specialist consumer ( B i = 0 .21), with the lowest value in 2015 ( B i = 0 .06). The overall TL was 4.6, indicating a secondary-tertiary consumer. The presence of prey from different habitats (benthic, epipelagic, reef, and mesopelagic) suggests a diversification strategy to reduce resource overlap between individuals. This apex predator exhibited trophic flexibility during ENSO, evidenced by a rapid response to anomalous environmental conditions that included reducing the foraging niche and increasing the consumption of prey from greater depths. These findings highlight the importance of this species as a bio-indicator for environmental changes around Galapagos Islands, a unique ecosystem that is a marginal habitat for this endangered species.

Background. The leopard grouper, Mycteroperca rosacea (Streets, 1877), is endemic to north-western 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. Conclusion. 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.

Intra-population resource partitioning is a foraging strategy that could minimize intra-specific competition. This behavior may be ecologically relevant for species in recovery like the Guadalupe fur seal Arctocephalus philippii townsendi (GFS), which was considered extinct 70–80 years ago. The present study provides, via scat and stable isotope (δ15N and δ13C) analyses, trophic knowledge around GFSs from Guadalupe Island just prior to and the 2013 breeding season, with emphasis on inter-individual variability. A total of 107 scat samples were analyzed, and 98 neonate fur samples (proxies for adult female foraging) were isotopically assessed. The overall trophic spectrum included 12 items, with a slight increase in diversity among main prey during the second half of the breeding season. The isotopic analysis revealed three distinct groups, reflecting apparent variations in trophic position and coastal/oceanic habitat use. As in previous studies, a mostly teutophagous diet was clear; however, our work is the first to identify inter-individual prey and habitat partitioning. Based on our results and those of other studies, GFSs exhibited an opportunistic foraging strategy across the breeding season. Both analyses were complementary in terms of diversification and useful for the understanding GFS foraging strategies, which are relevant to evaluating population recovery as factors such as prey availability is suggested to be critical to this species recovery.

We analysed a historical (1959–2017) database of blue marlin catches reported by the industrial pelagic longline fleet operating in the eastern Pacific Ocean. The time series of catch-per-unit-effort (CPUE) for the time period 1959–2015 was modelled as a function of temporal and environmental variables by using generalised additive mixed models (GAMM). CPUE predictions were made on an independent dataset (2016–2017). Results suggested that a higher nominal CPUE occurred near the equator during boreal winter, spring and autumn, with a shift towards the north during the boreal summer. Two high CPUE events were observed, one in the early 1960s and one in the early 1990s. The final GAMM explained 61% of the total variance of the CPUE time series. Only a small percentage of total deviance was explained by the environmental variables, so we suggest that changes in fleet-targeting practices are the main cause of the large variability in the time series. The final GAMM can be used to predict blue marlin CPUE with a prediction accuracy of 3–8 fish per 1000 hooks. We observed an important decline in CPUE from the early 2000s; the factors responsible for this decline should be further investigated.

The first record in Mexican waters of albinism and synophthalmia (partial cyclopia) in the Pacific angel shark, Squatina californica is presented. Albinism is not lethal, but synophthalmia may cause the death of the individual immediately after birth.

The sailfishIstiophorus platypterusis one of the most common billfish species in the Mexican Pacific. Information about its feeding habits in the coastal region of Acapulco, Guerrero is extremely limited. In the present study we quantified the diet of sailfish, based on captures made from March 2008 to December 2009 by the sport fishing fleet of Acapulco. We analysed a total of 561 stomachs, of which 254 contained food (45%). The size interval of examined specimens was between 101 and 212 cm postorbital length and between 15 and 47 kg total weight. In general, teleosts were the most important prey, followed by cephalopods. According to index of relative importance, the most important species in the diet were the fishAuxis thazard(63.04%) andFistularia commersonii(6.62%), followed by the cephalopodOctopusspp. (4.58%). There were no significant differences in the diet by sex (males and females), sexual maturity (immature and mature), or by season (warm and cold seasons). In all cases the most important prey species wasA. thazard. We conclude that the sailfishI. platypterusoff Acapulco behaves as a specialist predator because, despite the consumption of a high number of prey items, it feeds preferentially on a reduced number of prey species that form schools, and are available and abundant in the ocean.

Background. The San Jose and San Francisquito Islands and El Pardito Islet are important for recreational tourism, sport fishing, and commercial fishing. They are part of an “Area Natural Protegida” and “Area Prioritaria Marina”; however, studies on the composition and diversity of their marine floral and faunal communities are limited. To provide information vital for management and conservation of these islands, a check-list of the ichthyofauna was compiled based on original data and the data extracted from other sources. Materials and methods. Field methodology involved direct collecting of the specimens using a gill net or a charalera net and/or visual censuses. Records of fish present near the islands were either directly solicited from museum curators of national and international scientific collections or obtained by using online database collections. Additionally, an exhaustive literature search for fish records was carried out, including scientific articles, books, and theses. Finally, the preferential habitat and zoogeographic affinity of fishes were analyzed. Results. The data yielded 298 species representing 201 genera and assigned to 86 families, 36 orders, and two fish classes. The most numerous families in terms of the species number were Serranidae (23 species), Gobiidae (15 species), and Carangidae (14 species). The most numerous genera were Lutjanus and Halichoeres, with eight and six species, respectively. On average, there were 3.5 species per family. The fish community was dominated by tropical eurythermal species with wide distribution in the Eastern Pacific. An important component of endemic Cortez Province species was found, represented by 24 species from the families Chaenopsidae, Gobiidae, Labrisomidae, Tripterygiidae, Gobiesocidae, Dactyloscopidae, Kyphosidae, Opistognathidae, and Ophidiidae. Conclusion. The fish richness of the San Jose and San Francisquito Islands and El Pardito Islet represents 32% of the ichthyofauna recorded for the Gulf of California and includes 24 endemic species.

We provide the first record of a coho salmon, Oncorhynchus kisutch (Walbaum, 1792), off the west- ern coast of Baja California Sur, Mexico, approximately 690 km south of the previously reported distribution in the Northwest P acific. The specimen was captured in the regional commercial fishery. It was a female, 520 mm standard length, weighing 1855 g. Morphometric and meristic data are presented.

We determined total mercury (Hg) distribution in muscle and liver of ten ray species and assessed health risk considering Hg levels in muscle and average consumption of rays in Mexico. Rays were collected from five sites in NW Mexico between March and November 2012. Hg concentrations ranged from 4.465 μg g(-1) in muscle of the longtail stingray Dasyatis longa to 0.036 μg g(-1) in liver of the diamond stingray Dasyatis dipterura. Considering all the individuals, Hg in muscle (1.612±1.322 μg g(-1)) was significantly (p0.05) higher than in liver (0.745±0.616 μg g(-1)). Regarding local health risk assessment, none of the ray species may cause adverse effects on consumers.