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The cannonball jellyfish Stomolophus meleagris display colour variations from blue to purple, and different pigmentation patterns on the umbrella surface. Although these colour phenotypes are commo...

Graceful mojarra (Eucinostomus gracilis) is an important component of the ichthyic fauna of lagoon systems but knowledge of its population aspects is scarce. Monthly samples in the Magdalena-Almejas Lagoon system (March-August, 2014-2017) were obtained with a trawling net. Abundance was estimated using the swept area method and its spatial variation; and the maturity size was determined using the logistic method. The sex ratio for mature and immature populations, and their length-weight relationship were estimated; FISAT was used to estimate the growth and recruitment parameters. Abundance ranged from 0.6 to 203 ind-Ha-1 with changes for each lagoon system areas and among years. Size at maturity (L50) was 132 mm in total length (TL) for the population, 129 mm TL females, and 135 mm TL males. Considering the population of the total organisms, L50 indicated that 18% were adults and 82% were juveniles. Juvenile dominance indicated that this lagoon system is used for grow-out. The smaller ratio of adult organisms does not allow asserting assertion that the priority of the area is for reproduction. E. gracilis showed moderate growth (K = 0.56 year-1) with longevity of 5.4 years and asymptotic length of L∞ = 195 mm.

Worldwide catches of cannonball jellyfish Stomolophus meleagris (Cnidaria: Scyphozoa) have increased during the last years; nevertheless, this species still lacks updated biological knowledge for its management. This research proposes that the individual growth pattern for jellyfish can be estimated in the absence of age readings through cohort follow-up over time and by multi-model inference approach (MMI). Length data were obtained during 2010–2011 in Gulf of California to obtain cohort information using a multinomial analysis and then assign age; growth model selection was based on MMI. Three cohorts were identified and the von Bertalanffy model suitably described their growth. The species has an accelerated growth with a short life cycle; cohorts one and two reached their asymptotic length, and the third one barely reached the length-at-first sexual maturity. Growth variations among cohorts could be explained by their different biological strategies where the first two prioritized asymptotic length and the third one reproduction length. The three cohorts shared a common goal for medusoid phase, which was sexual reproduction. This information could be used for estimating harvest rates or assessing their capacity for redoubling as an invasive population in coastal ecosystems. The proposed methodology may be applied in other jellyfish species around the world.

This study provides information on feeding habits of the lizardfish Synodus scituliceps, one of the most abundant and frequent species in shrimp by-catch in the demersal area in the eastern coast of the Gulf of California, Mexico. Stomach content analyses were performed on 114 organisms caught from August 2004 to March 2005, and Levin's index was applied. The most important prey species were benthic fishes: Eucinostomus currani, Opisthonema libertate, Synodus lucioceps and Paralichthys californicus. According to the Levin’s index (Bi = 0.39), S. scituliceps is a piscivorous specialist predator in soft bottoms, with similar diet in juveniles and adults.

Exploitation of the cannonball jellyfish (Stomolophus sp. 2) is increasing in Mexico and USA due to successful fisheries associated with seasonal blooms in coastal areas. Previously, it was proposed that such blooms could be identified by recognizing the presence of young stages in the water. In our work, we aim to describe the young stages (ephyra and metaephyra) found in the Las Guásimas lagoon, Sonora, Mexico. The description of specimens is based on photographs, drawings, and morphological measurements aimed at helping in the early detection of blooming events.

Environmental changes have been associated with natural climatic variability and/or human activity. External forcing as the North Atlantic Oscillation (NAO) have implications in the global and regional hydrological balance. Previous data in the Tampamachoco lagoon, in Mexico, for the past 54 years, shows changes in the fish assemblage. Therefore, in the present study, a time series of water temperature from 1922 to 2020 data was processed detecting periodic cycles of 34 and 17 years. Additionally, multivariate analyses of the historical data from the fish assemblage from the past 54 years and 2020 were correlated with temperature anomaly and NAO; moreover, fishery catches were correlated to climatic events. Furthermore, a survey was made in 2020 to local fisheries to assess the socioeconomic impact of the early months of the COVID-19 pandemic. Tampamachoco lagoon is facing multiple stressors such as: climate variability and human activities that are leading to a collapsing ecosystem with low resilience.

Coastal zones are important areas for the development of diverse ecosystems. The analysis of chlorophyll a (Chl a), as an indicator of primary production in these regions, is crucial for the quantification of phytoplankton biomass, which is considered the main food chain base in the oceans and an indicator of the trophic state index. This variable is greatly important for the analysis of the oceanographic variability, and it is crucial for determining the tendencies of change in these areas with the objective of determining the effects on the ecosystem and the population dynamics of marine resources. In this study, we analysed the Chl a concentration distribution on the mainland coast of the Gulf of California based on the monthly data from July 2002 to July 2019, obtained from remote sensing (Moderate-Resolution Imaging Spectroradiometer Aqua (MODIS-Aqua) with a 9 km resolution). The results showed a clear distribution pattern of Chl a observed along this area with the maximum levels in March and minimum levels in August. A four-region characterisation on this area was used to make a comparison of the Chl a concentrations during warm and cold periods. The majority of the results were statistically significant. The spectral analysis in each of the four regions analysed in this study determined the following variation frequencies: annual, semi-annual, seasonal, and inter-annual; the last was related to the macroscale climatological phenomena El Niño-La Niña affecting the variability of the Chl a concentration in the study region.

This study provides information on the population dynamics of the smooth hammerhead shark Sphyrna zygaena in the central-southeast Pacific Ocean. The samples were obtained from artisanal fisheries from 2008 to 2013 to analyse cohorts, growth, mortality, abundance and recruitment using methods based on length and relative age and an inference multi-model. According to the von Bertalanffy growth model, the results indicated that the species showed from three to seven cohorts annually and slow growth (Wi = 57.20%): L∞ = 292.86 cm, K = 0.141 per year and t0 = -2.26. Length of sexual maturity was 239.30 and 209.10 cm at first capture; the average natural mortality value was 0.231 per year, by fishing 0.051 per year with a total mortality of 0.26 1 per year and exploitation rate of 0.15. Interannual variability was recorded in biomass with an average of 7367.24 tonnes, as well as a spatial permanence pattern. The results suggest that the La Nina event biologically favours the population in the area. The information from this study is essential for better understanding the species population and serves as a basis for future actions of management and conservation of S. zygaena.

Immigration density magnitude and entry sizes of shrimp postlarvae to Terminos Lagoon were analyzed through sixteen fortnightly sampling from March to November in 2013, in three levels in the deepest channel of the Puerto Real inlet. Trapezium nets were used with 1.5 m length, 50 cm mouth diameter and 505 μm mesh, during each sampling 12 casts of 15 minutes/each were made. It was determined the presence of two species Litopenaeus setiferus and Farfantepenaeus duorarum, with total densities of 41.284 and 37.558 Pls 100 m-3 respectively. The annual cycle of immigration of postlarvae was very similar for both species, with a clear pattern of immigration throughout the year, linked to climatic variation, with the highest densities (88%) during rainy season. There were two periods of maximum density, related to the periods of greatest reproduction of these species. The density variation among cast reflects the presence of at least two and probably more postlarvae banks, located some closer than others to the mouth of the lagoon and with different densities in them. The average sizes of the two species were 7.9 mm total length of L. setiferus and 9.0 mm of F. duorarum. The differences in income sizes of both species seem to indicate the habitat preference of adult populations, L. setiferus occurring in more coastal areas than F. duorarum. Considering the variation in density and sizes throughout each sampling period, it is evident that the larvae on the banks belong to different cohorts and that have coincided in their location in front of the mouth.

The aim of this study was to determine the presence of the white spot syndrome virus (WSSV) in zooplankton organisms collected from an important shrimp-culture area of the Gulf of California. Environmental water parameters (temperature, salinity, dissolved oxygen, and pH) were monitored, and zooplankton was collected. Samples were sectioned according to taxonomic groups (from Phylum to Family) for the detection of WSSV via PCR. A total of 52 zooplankton taxa were identified, of which crustaceans were the most abundant (82%). From the 228 WSSV diagnoses performed, 35% were positive. Moreover, from 32 taxa recorded at least one positive result was observed during the study, and only 13 were negative in all tests. The highest prevalence was observed in three taxa of copepods, brachyurous and bivalves. However, considering prevalence and frequency of occurrence, it was determined that up to 12 taxa could be considered as high-risk vectors. Finally, a significant correlation was found between the number of diagnoses per station with biovolume (rs = 0.817) and taxa richness (rs = 0.995). The results suggest that zooplankton diversity and abundance are associated with virus dispersion; moreover, these results demonstrated that the dispersion capacity of the virus through different taxa has been probably underestimated in recent years.

Background. The presence of Laemonema verecundum (Jordan & Cramer, 1897) had not been previously reported at depths less than 666 m. Goals. The objective of the research was to study the bathymetric distribution of L. verecundum. Methods. In the eastern continental shelf of the Gulf of California, 648 specimens of L. verecundum were collected during two experimental research cruises in September 2004 and February 2005. Results. Specimens were collected at depths between 165 and 483 m, where temperatures ranged between 9.5 and 19.9° C, and average oxygen concentration was 1.7 mg/l. Conclusions. This new record expands the known bathymetric distribution range of this species inhabiting shallow waters in the gulf.

Biometric relationships were estimated for the three most important shrimp species on the coasts of the Gulf of California, Mexico. Individuals were obtained from six lagoon systems, and offshore sites along the east coast of the Gulf of California, mainly in the state of Sonora, between March and September of 2015 and 2016. A total of 25,764 individuals of Penaeus stylirostris, Penaeus vannamei and Farfantepenaeus californiensis were analyzed; the length and weight regression for the females, males and combined sexes showed a high correlation between variables. Additionally, some statistically significant differences were found in the linear length and weight relationships (P < 0.05) between sexes. This study reports the length-weight parameters for a key site of the shrimp fishery, it covers a wide range of sizes for each species and was based on the stages late inshore juvenile and offshore of the shrimp lifecycle; as such, this study provides useful information for future estimations of indispensable parameters for stock assessment analyses.

Aspects of distribution and population dynamics were assessed in two rock shrimp species of the genus Sicyonia . Samples were obtained by sea bottom trawling in depths from 50 to 460 m during two research cruises on board the B/I BIP XII in the Gulf of California, Mexico. Taxonomic identification of specimens was performed; measurements of individual length and weight data were taken to obtain biometric relationships and length frequencies. Growth parameter estimations were performed adjusting the von Bertalanffy growth model (VBGM), and the recruitment pattern was obtained by the ELEFAN II method. Longevity was estimated with the Taylor equation, natural mortality with six different models, and length at first maturity by the logistic model. A total of 67 fishing trawls were monitored, and 1,330 specimens were caught (65% S. ingentis ; 35% S. penicillata ) in the depth range from 124 to 338 m. Sex ratio (F:M) was 1.0:1.6 for both species; weight and length relationships (both sexes) showed an isometric growth for S. ingentis and positive allometric growth for S. penicillata . Growth parameters and longevity values were moderate (1.71 and 1.81 years) with age at first maturity around six months for both species. The recruitment pattern showed continuous periods all year long, with a notable peak from November to May. Average natural mortality was 2.47 for S. ingentis and 2.35 for S. penicillata . Distribution and population dynamics information reported in this study for these two shrimp species should be considered as base knowledge in subsequent studies on fisheries management in the Gulf of California.

Oceanic mesoscale events such as eddies, coastal upwelling, filaments and fronts created by water mass intrusion present properties allowing them to concentrate, transport and disperse salt, nutrients and plankton, among other important constituents in the ocean. The use of satellite images enables the continuous monitoring of the ocean dynamics at different temporal and spatial scales, aiding the study of its variability. This study focuses on the identification of these mesoscale events in the Gulf of California (GC) by means of sea surface temperature (SST) and chlorophyll a (Chl a) fronts (edge) detection by processing 5-day satellite images from the 1998–2019 period. The annual occurrence or frequency and duration of each event was identified; the interannual variability was evaluated and underlying correlations with the Multivariate El Niño Index (MEI) and the Pacific Decadal Index (PDOI) were assessed via Principal Component Analysis. Most events showed a seasonal variability due to the seasonal behavior of forcing agents (i.e., Pacific Ocean and winds) that stimulate their formation or presence in the GC; seasonality was more evident in the northern region than in the southern region. The interannual variability of their frequency or duration was associated with strong and intense El Niño and La Niña conditions (positive or negative MEI values) together with positive or negative phases of the PDOI. The use of SST and Chl a satellite images with a 5-day temporal resolution allowed to better identify and quantify the annual frequency and duration of each mesoscale event. It allowed to detect a seasonal behavior of these events in the northern region, followed by the central region. The southern region, due to the interaction of different water masses with unique characteristics, exhibited a less evident seasonality in the frequency of eddies, and no apparent association between their interannual frequency and duration with the MEI and PDOI. Constantly monitoring these oceanic events and their variability will help in the understanding of how the different regions of this large marine ecosystem respond to these variations in the long term.

The knowledge of the population dynamics and changes of biomass of harvested marine species is relevant for fisheries management. In this study, a catch-at-age analysis for jumbo squid Dosidicus gigas called CAGEAN-JS model was implemented. So, for illustrative purposes and based on the best biological and fishery data available, the advantages of the catch-at-age model are described and modeled as an alternative statistical method useful for stock assessment in jumbo squid fishery, improving the biomass and recruitment estimations in the population. A matrix was implemented that included catch-at-age data using a time step of the matrix of 30 days with a fishing period or time expressed in months. Numbers of squid caught at time (age) and fishing period (months) were estimated from the commercial catch using an age-length key and weight-at-length relationship. Catch and catch rate data for 2001 and 2002 fishing seasons from three different fleets were used to provide extra structure to the CAGEAN-JS model. The model estimated a total biomass of 798,084 t (C.I. 781,435–837,679 t, P P

RESUMEN. Se presenta la composición de especies de peces y sus aspectos biogeográficos de la Laguna Las Guásimas, localizada en el sector central del Golfo de California. Se realizaron siete campañas estacionales de muestreo y las colectas se efectuaron con tres artes de pesca: atarraya, chinchorro de línea y red de arrastre. Se observaron 95 especies representadas por 16 órdenes, 38 familias y 67 géneros. Las familias mejor representadas por su número de especies fueron: Carangidae, Sciaenidae, Haemulidae, Paralichthydae, Engraulidae y Gerreidae. Además se identificaron tres especies endémicas del Golfo de California (Micropogonias megalops, Leuresthes sardina y Pleuronichthys ocellatus). El análisis de afinidad biogeográfica mostró una alta dominancia de especies distribuidas en el Pacífico Oriental Tropical (Provincia de Cortés y Panámica) y especies transicionales entre la Provincia de California y el Pacífico Oriental Tropical (POT). Utilizando investigaciones sobre peces efectuadas anteriormente en la localidad, se realizó una comparación entre las especies previamente registradas en la localidad y las registradas en esta investigación, utilizando como indicadores la vulnerabilidad y resiliencia. Se observaron cambios en la estructura de la comunidad a lo largo de tiempo, que pudieran ser inducidos por cambios ambientales, actividades antropogénicas como la pesca y/o la dinámica del ecosistema. La mayoría de las especies que son nuevos registros (84%), mostraron vulnerabilidades de moderadas a altas, enfatizando la alta importancia de la laguna como área de crianza y protección de estas especies.

Jellyfish are non-model organisms that have brought the scientific community's attention over the last decades since the frequency and intensity of these species blooms around the world have increased significantly. The occurrence of blooms has been hypothesized due to the rise in seawater temperature associated with climate change. This fact has promoted an increased interest in studying jellyfish metabolic responses to face thermal stress and maintain cell homeostasis. In this study, the response of the cannonball jellyfish Stomolophus meleagris to short-term exposure to different temperatures was evaluated. The survival and respiratory rates, and the concentration of glucose, L-lactate, glycogen, ATP, and total soluble protein in the umbrella of adult jellyfish were measured. Low survival rates at extreme temperatures (18 and 33 °C) and an increase in the jellyfish respiratory rates were observed as seawater temperature raised. Rapid changes were detected in energy substrates such as glucose and glycogen that significantly varied at extreme temperatures and longer exposure periods. L-lactate levels increased after 2 h of exposure, and then remained steady at longer times of exposure. Soluble protein concentration decreased significantly in jellyfish exposed to extreme temperatures, and ATP increased after exposure to non-optimal temperatures (18, 28, and 33 °C). These results suggest that S. meleagris faces temperature changes through rapid metabolic responses that use energetic reserves, activate anaerobic metabolism, and display a remarkable ability to synthesize ATP and maintain energy, even at long exposure.

Developing countries may face many obstacles in managing their resources and in assigning conservation status to certain groups or species. One of the main obstacles is the lack of basic and reliable information on habitat of species or ecosystems. Sustainable species management is difficult to attain without this information. A key piece of information about any resource is their distribution and abundance. Shrimp of the genus Sicyonia are poorly known globally in their biology although they have been exploited in several parts of the world. This study analyzed their distribution, abundance and size structure in the Gulf of California (GC) and the western coast of the Baja California Peninsula (WCBCP). From a total of 207 trawling tows performed (73 in the GC and 134 in the WCBCP) at depths from 45 to 600 m from 2004 to 2006, organisms (N = 4205) from four species (S. disdorsalis: 1 849; S. ingentis: 1405; S. penicillata: 965; and S. picta: 71) were caught. Of the four species found in the GC, the most frequent and abundant were S. penicillata and S. ingentis. Only three of the species, S. disdorsalis, S. ingentis and S. penicillata, were found in the WCBCP, of which S. disdorsalis and S. ingentis were the most frequent and abundant. The relationship between S. disdorsalis, S. ingentis and S. penicillata abundance and depth showed significant associations. The sizes of each species were different between the two areas. This study reports a range extension in the bathymetric distribution to 174 m for S. picta, 199 m for S. ingentis, and 259 m for S. disdorsalis, and provides more information on size structure of the four species of the genus Sicyonia still unknown to date.

First report of the dynamic populations (structure size, growth, size at first maturity, longevity, natural mortality, and recruitment pattern) of black brotula Cherublemma emmelas in the Gulf of California. Growth parameters (L, k and to) were estimated using the von Bertalanffy model. The ELEFAN II method was used to estimate recruitment pattern and Taylor’s equation to estimate longevity. Natural mortality was determined using Pauly’s equations and Jensen’s. Size at first maturity was obtained by adjusting a logistics model. During four cruises on board the BIP-XI research ship, 2148 specimens were caught at 119-499 m depth in February and May 2005, and June and October 2007. The size structure showed a bimodal distribution with lengths from eight to 32 cm of total length and 15.9 cm average size. The biometric relationship between weight and length showing allometric growth rate (b ≠ 3) for sex. The fitted growth parameters were L ∞ = 33 cm; k = 0.6 yr -1 ; t o = -0.26 year indicated a moderate growth, while longevity was five years of age. Size at first sexual maturity was 18.8 cm, and natural mortality was 0.77 yr -1 (by Pauly) and 0.90 (by Jensen). The recruitment pattern showed peaks in June and July. Normal 0 21 false false false ES-MX JA 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-top:0cm; mso-para-margin-right:4.8pt; mso-para-margin-bottom:6.0pt; mso-para-margin-left:0cm; text-align:justify; line-height:150%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri",sans-serif; mso-bidi-font-family:"Times New Roman"; mso-ansi-language:ES-MX; mso-fareast-language:ES-MX;}

The coastal zones are areas with a high flow of energy and materials where diverse ecosystems are developed. The study of coastal oceanography is important to understand the variability of these ecosystems and determine their role in biogeochemical cycles and climate change. Sea surface temperature (SST) analysis is indispensable for the characterization of physical and biological processes, and it is affected by processes at diverse timescales. The purpose of this work is to analyze the oceanographic variability of the Eastern Coastal Zone of the Gulf of California through the study of the SST from time series analysis of monthly data obtained from remote sensors (AVHRR-Pathfinder Version 5.1 and Version 5 resolution of 4 km, MODIS-Aqua, resolution of 4 km) for the period 1981 to 2016. The descriptive analysis of SST series showed that the values decrease from south to north, as well as the amplitude of the warm period decrease from south to north (cold period increase from south to north). The minimum values occurred during January and February, and ranged between 18 and 20 °C; and maximum values, of about 32 °C, arose in August and September. Cluster analysis allowed to group the data in four regions (south, center, midriff islands and north), the spectral analysis in each region showed frequencies of variation in scales: Annual (the main), seasonal, semiannual, and interannual. The latter is associated with the El Niño and La Niña climatological phenomena.

This study describes the first record of the whale shark Rhincodon typus association with the cannonball jellyfish Stomolophus meleagris in the Gulf of California, Mexico. Whale sharks were observed swimming and feeding among swarms of jellyfish, suggesting competition and predatory behaviour given the overlap in food preferences between both species. This finding is relevant because of the species-wide distribution and the importance of these interactions, which should be considered in conservation strategies of R. typus and management of cannonball jellyfish fisheries.

The immigration of white shrimp Penaeus setiferus (Decapoda: Penaeidae) postlarvae (Pls) into the Terminos Lagoon was studied to determine the annual pattern of abundance and its relationship with temperature, salinity, tidal current velocity, and river discharge. Zooplankton samples were simultaneously obtained fortnightly at surface, mid-water, and bottom. The nets used were 50 cm in diameter, 1.5 m in length and 505 μm mesh size. The results indicated a postlarval seasonal immigration pattern, with the lowest average density values from March to May and October to November, and significantly higher values from June to September; maximum peaks occurred in June and September. High Pls densities were obtained between one and three hours after the tidal inflow started. Temperature and salinity varied little during each sampling period and had no apparent effect on immigration, but did have an effect on the seasonal abundance cycle. The multiple regression models indicated that the tidal current velocity and the temperature explained 86% of the variation in Pls abundance during immigration to the Terminos lagoon. The larval migration varied at different levels, with highest densities occurring at a medium depth of 5 m. The Pls entered an optimal range of tidal current velocity (between 0.6 and 0.9 m3 s-1). The main entry mechanism was through the tide current of the Selective Tide Stream Transport, where the Pls could also select an optimum current velocity, avoiding the strata of higher turbulence that would imply higher energy expenditures.

The Northern Gulf of California (NGC) is a mega diverse area of high endemism with major economic interest because of the multi-specific fisheries developed, mainly shrimp. There is a lack of recent studies on bycatch fish assemblages, so during the fishing seasons from 2009-2010 and 2010-2011, on board 13 shrimp boats, 14 commercial fishing trips were performed from 5 m - 90 m in depth with a total of 119 catches. The 119 catches were analyzed to assess fish community structure using taxonomic diversity indices to detect changes in the community following the taxonomic distinctness average Δ+ and the diversity index Δ* (TAXDEST of the PRIMER v6 program). To confirm the structure of functional groups, we considered similarities of ecologic and morphologic traits among species. The results showed that the indices Δ+ and Δ* were within the expected average and confidence intervals at 95%, finding significant differences between the indices. The analyses showed a well-structured community because of the great variety of forms and functions of the species within the community. In the community of the functional groups, reproduction was the ecological attribute that contributed the most to their structure. The community structure was represented by intermediate trophic levels (3-3.9), preferably primary and secondary carnivores within the trophic categories of predators of benthic ichthyo-fauna that belong to demersal species of soft bottoms and mostly fusiform body. To conclude, the NGC showed high functional redundancy according to the estimated functional groups, thus the ecosystem was considered stable and with great diversity. This type of studies should be followed using fishing and environmental effort due to the great biological and ecologic importance in the area.

The diet and feeding pattern of scyphomedusa Stomolophus meleagris (Rhizostomeae) was studied, by comparing stomach samples from different developmental stages and environmental zooplankton with the aim to determine diet composition, trophic niche breadth, selectivity and feeding overlap of this edible jellyfish species. Samplings were performed during April and December 2010 and in January 2011, in the coastal lagoon Las Guásimas (27°49′–27°54′N 110°40′–110°35′W), central Gulf of California, which consisted of zooplankton tows and jellyfish collections for stomach content. More than 39 prey items were identified in the gut contents (N = 69), from which eight taxa formed over 90% of the total. Fish eggs were considered main prey (58.6%), copepods (10.8%), veliger larvae of gastropod (13.0%) and bivalve (12.7%) were secondary prey while cirriped and decapod larvae were incidental prey (S. meleagris is a specialist predator and Pearre's index showed positive selection of fish eggs, gastropods, bivalves and cirripeds while selectivity was negative for copepods and appendicularians. The relative timing of these changes suggests that ontogenetic processes are closely related with shift in the diet, which indicates increasing predation pressure during development of the medusoid stage of this species, thus emphasizing their ecological importance in coastal ecosystems.

Algunas especies de lenguados son capturadas incidentalmente con redes de arrastre y algunas de estas son especies objetivo de una pesqueria artesanal en el Golfo de California, Mexico. Con el proposito de conocer cuantos individuos de la poblacion estan siendo capturados y cuales son los efectos de estas capturas, el objetivo de este estudio fue estimar la abundancia de los lenguados capturados incidentalmente con redes de arrastre y en una pesqueria artesanal o de pequena escala en el Golfo de California, y determinar la posible competencia entre flotas (con redes de arrastre y la flota artesanal con redes agalleras) por el mismo recurso. Las muestras fueron recolectadas durante 2002 y 2003 de 3 diferentes fuentes: prospecciones de 2 barcos de la flota camaronera comercial, prospecciones en 2 cruceros de investigacion y de una flota artesanal la cual opera a lo largo de la costa del estado de Sonora, Mexico. La abundancia de los lenguados capturados en las redes de arrastre fue estimada usando el metodo de area barrida y a traves de analisis de cohortes por talla fue estimada la abundancia para los lenguados capturados por la flota artesanal. Catorce especies de lenguados fueron identificados en las capturas incidentales con redes de arrastre, destacando Paralichthys woolmani, Etropus crossotus, Citharichthys fragilis, Citharichthys gilberti, Achirus mazatlanus y Syacium ovale. Seis de las 14 especies de lenguados capturados incidentalmente fueron tambien capturados por la flota artesanal, de la cual el 70% corresponde a P. woolmani. Se demostro que cada flota opera sobre diferentes fracciones de la poblacion, individuos de 25 a 90 cm en longitud total fueron capturados por la flota artesanal y los valores de mortalidad por pesca y tasa de explotacion fueron < 0,01, mientras que en las capturas incidentales (flota camaronera) los individuos presentaron tallas entre 4 y 20 cm, demostrando presion de pesca en los individuos juveniles cuya captura podria tener efectos negativos, debido a estos pueden ser reclutas para la pesca artesanal.

espanolLas lagunas costeras se caracterizan por su alta diversidad, riqueza y abundancia de peces, las cuales pueden ser modificadas por la variabilidad de las condiciones ambientales. El presente estudio tiene como objetivo describir la estructura de la comunidad de peces y relacionar su variabilidad estacional con los parametros de temperatura y salinidad en una laguna costera. Durante 6 campanas de muestreo se recolectaron 4.199 peces, agrupados en 95 especies. Los resultados indicaron que la riqueza, diversidad y equidad tuvieron un comportamiento estacional similar con valores mayores durante otono 2010, primavera 2011 y 2012; la abundancia fue mayor en otono 2010, verano 2011 y 2012 y la biomasa en otono 2010 y verano 2011. La relacion de la temperatura y salinidad a traves del analisis RDA con los parametros ecologicos, indico que algunas de las especies dominantes son de afinidad calida y otras de afinidad fria. Mientras que la riqueza y diversidad se incrementan durante temporadas frias, la biomasa y equidad aumentan en las temporadas de mayor salinidad; por su parte la abundancia se incrementa en temporadas calidas. Las curvas ABC mostraron estres moderado durante invierno y verano de 2012 y el MDS indico la formacion de 4 grupos, dos integrados por 2 periodos de muestreo y dos por uno solo de ellos. Los parametros ecologicos presentaron variaciones estacionales debido a la influencia de los cambios en temperatura y salinidad. EnglishCoastal lagoons are characterized by high diversity, richness, and abundance of fishes, which can be modified by high variability of environmental conditions. The present study aims to describe the structure of the fish community and related its seasonal variability with temperature and salinity in a coastal lagoon. During 6 seasonal sampling campaigns 4,199 fish were collected and grouped in 95 species. The results indicated that richness, diversity and evenness indices showed similar pattern with higher values in autumn 2010, spring 2011 and 2012, abundance was higher in autumn 2010, summer 2011 and 2012 and biomass in autumn 2010 and summer 2011. Relationship of temperature and salinity through the RDA analysis with ecological parameters indicated that some dominant species are of warm affinity and other of cold affinity. Richness and diversity increase during cold seasons, while biomass and evenness increase in seasons of higher salinity and abundance increases in warm seasons. The ABC curves showed moderate stress in winter and summer 2012 and MDS indicate the formation of 4 groups, two integrated by 2 sampling periods and two by single sampling period. Ecological parameters showed seasonal variations because they are influenced by changes of temperature and salinity.

We analyzed mantle length and age data of the whole ontogenic cycle of the jumbo squid Dosidicus gigas in the Gulf of California, Mexico, to describe its growth pattern. Several individual growth models that included asymptotic and non-asymptotic patterns were fitted to the data, and Akaike’s information criterion and multimodel inference were used to identify the model that best fit the data. The length-at-age data were divided into males and females (recruits and adults) for analysis separately and then combined to assess the overall growth pattern. The Schnute general model ( ρ ≠ 0, η ≠ 0, where ρ is the constant relative rate of the relative growth rate, η is the incremental relative rate of the relative growth rate) was the function that best described the growth of females, males and both sexes of D. gigas together. For females, the Akaike difference and Akaike weight were 0 and 0.91, respectively; for males, the Akaike difference was also 0, but the Akaike weight was 0.39, showing that alternative growth models could explain the individual growth; these growth models were the Gompertz (L0, length at time zero), Gompertz (L∞, asymptotic length) and Schnute (ρ ≠ 0, η = 0) models. We estimated the age and mantle length at which the growth rate changes for both sexes, estimating an age of 162.36 d (separately, 167.51 d for females and 158.98 d for males), and a length of 299.52 mm for the growth inflection point (separately, 312.84 mm for females and 292.86 mm for males). Once D. gigas reaches this point, the species exhibits more gradual growth until reaching an asymptotic mantle length of 859.45 mm (for females, 904.80 mm, and for males, 828.49 mm). A comparison of the growth patterns of D. gigas reported in the Eastern Pacific indicated non-asymptotic growth of this species in the Humboldt Current and Costa Rica Dome; in contrast, asymptotic growth was identified for the western coast of Baja California and Gulf of California. The reason for this difference is unclear, and this issue will be a topic of future studies.

The trophic spectrum of bothEucinostomus entomelasandMicropogonias megalops, the two most abundant fish species in Laguna Las Guásimas, Sonora, México is described in our study. A total of 21 types of prey were identified belonging to seven taxonomic groups (Crustacea, Mollusca, Annelida, Rhodophyta, Copepoda, Echinodermata and Chordata) to analyse the feeding spectra and diet breadth. The preferred prey items ofEucinostomus entomelas(Dark-spot mojarra) were Polichaeta (index of relative importance = 46.7%), followed by bivalves(36.6%), andLuidia columbia (5.6%), while those ofMicropogonias megalops(Bigeye croaker) were Portunidae (22.8%) followed by Gammaridae (20.55%) and Crustacea (18.37%). The trophic spectrum for maleE. entomelawas composed of Bivalvia and Polychaeta. Both predators showed low values in diet breadth (E. entomelas(Levin's indexBi = 0.14) andM. megalops(Levins's indexBi = 0.43)). The low trophic overlap (Cλ = 0.14) between predators suggests that both fish are not competing with each other for food resources in Laguna Las Guásimas.

Population dynamics of 3 Callinectes species: C. arcuatus, C. bellicosus, and C. toxotes are reported for the first time as incidental shrimp bycatch samplings captured in the eastern Gulf of California in a range from 10 to 77 m in depth from September 2004 to March 2005. Growth, longevity, recruitment pattern, mortality (natural, total, and by fishing), and exploitation rate were analyzed. Also, size comparison among the organisms captured by the shrimp and artisanal fishing fleets was calculated. Callinectes arcuatus (n = 737) was more abundant than the other two (C. bellicosus, n = 291 and C. toxotes, n = 344). Significant differences were shown between size distribution of C. arcuatus and C. bellicosus captured by the 2 fleets; the shrimp fleet extracted mainly organisms in sizes ranging from 50 to 120 mm in carapace width (CW), while the artisanal fleet extracted sizes from 75 to 155 mm in CW from both species. Growth parameters were moderate (L∞= 160, 173, and 168 mm; K= 1.1., 1.3 and 0.9 year-1 for C. arcuatus, C. bellicosus, and C. toxotes, respectively), estimating a 4-year longevity for the 3 species. The reproductive recruitment pattern showed a continuous period with a peak from May to August. The exploitation rate did not show a significant degree of overexploitation for any of the species. There are some differences in the parameters of population dynamics (sizes, growth) of this species based on data from commercial captures and those obtained with data of incidental captures. It is important to perform an analysis including both types of information for an adequate fishery management of these resources.