Phylogenetic relationships of sleeper gobies (Eleotridae: Gobiiformes: Gobioidei), with comments on the position of the miniature genus Microphilypnus.

Microphilypnus and Leptophilypnion are miniaturized genera within the family Eleotridae. The evolutionary relationships among these taxa are still poorly understood, and molecular analyses are restricted to mitochondrial genes, which have not been conclusive. We compiled both mitochondrial and nuclear genes to study the phylogenetic position of Microphilypnus and the evolutionary history and relationships of eleotrids. We propose that Microphilypnus and Leptophilypnus (a non-miniature genus) are not sister groups as suggested by previous studies, but rather separate lineages that arose in the early Eocene, with Leptophilypnus recovered as a sister group to the other analyzed eleotrids. In fact, Microphilypnus is currently associated with the Neotropical clade Guavina/Dormitator/Gobiomorus. We also identified a well-supported clade that indicated Gobiomorus and Hemieleotris as paraphyletic groups, besides a close relationship among Calumia godeffroyi, Bunaka gyrinoides, Eleotris and Erotelis species. This is the first comprehensive report about the evolutionary relationships in members of the family Eleotridae, including multiloci and multispecies approaches. Therefore, we provided new insights about the phylogenetic position of some taxa absent in previous studies, such as the miniature genus Microphilypnus and a recently described species of Eleotris from South America.

Genetic structure and historic demography of endangered unarmoured threespine stickleback at southern latitudes signals a potential new management approach.

Habitat loss, flood control infrastructure, and drought have left most of southern California and northern Baja California's native freshwater fish near extinction, including the endangered unarmoured threespine stickleback (Gasterosteus aculeatus williamsoni). This subspecies, an unusual morph lacking the typical lateral bony plates of the G. aculeatus complex, occurs at arid southern latitudes in the eastern Pacific Ocean and survives in only three inland locations. Managers have lacked molecular data to answer basic questions about the ancestry and genetic distinctiveness of unarmoured populations. These data could be used to prioritize conservation efforts. We sampled G. aculeatus from 36 localities and used microsatellites and whole genome data to place unarmoured populations within the broader evolutionary context of G. aculeatus across southern California/northern Baja California. We identified three genetic groups with none consisting solely of unarmoured populations. Unlike G. aculeatus at northern latitudes, where Pleistocene glaciation has produced similar historical demographic profiles across populations, we found markedly different demographics depending on sampling location, with inland unarmoured populations showing steeper population declines and lower heterozygosity compared to low armoured populations in coastal lagoons. One exception involved the only high elevation population in the region, where the demography and alleles of unarmoured fish were similar to low armoured populations near the coast, exposing one of several cases of artificial translocation. Our results suggest that the current "management-by-phenotype" approach, based on lateral plates, is incidentally protecting the most imperilled populations; however, redirecting efforts toward evolutionary units, regardless of phenotype, may more effectively preserve adaptive potential.

Population-level morphological variation of Anisotremus interruptus (Gill, 1862) (Perciformes: Haemulidae) in the Tropical Eastern Pacific, with the description of two new species.

The family Haemulidae is a wide-ranging group of marine fishes that are of significant commercial value in the Tropical Eastern Pacific (TEP). Phylogenetic studies on the species Anisotremus interruptus have revealed high levels of genetic diversity as well as divergence among populations in the TEP, which suggests that the taxonomic diversity of A. interruptus could be underestimated. Anisotremus interruptus has a large distribution, ranging from central Baja California, Mexico to northern Peru, including all oceanic islands except Clipperton. Recent genetic studies on this taxon indicate the presence of a species complex of at least three distinctive lineages. We performed a comparative study of the population-level meristic and morphometric variation of A. interruptus in the TEP to evaluate and identify possible morphological features concordant with the genetic differentiation of populations. Our results provide evidence of the presence of two new species of the genus Anisotremus, A. perezponcedeleoni sp. n. from the Revillagigedo Archipelago and A. espinozai sp.n. from Galapagos Archipelago-Cocos Island.

Age-Appropriate Wisdom? : Ethnobiological Knowledge Ontogeny in Pastoralist Mexican Choyeros.

We investigate whether age profiles of ethnobiological knowledge development are consistent with predictions derived from life history theory about the timing of productivity and reproduction. Life history models predict complementary knowledge profiles developing across the lifespan for women and men as they experience changes in embodied capital and the needs of dependent offspring. We evaluate these predictions using an ethnobiological knowledge assessment tool developed for an off-grid pastoralist population known as Choyeros, from Baja California Sur, Mexico. Our results indicate that while individuals acquire knowledge of most dangerous items and edible resources by early adulthood, knowledge of plants and animals relevant to the age and sex divided labor domains and ecologies (e.g., women's house gardens, men's herding activities in the wilderness) continues to develop into middle adulthood but to different degrees and at different rates for men and women. As the demands of offspring on parents accumulate with age, reproductive-aged adults continue to develop their knowledge to meet their children's needs. After controlling for vision, our analysis indicates that many post-reproductive adults show the greatest ethnobiological knowledge. These findings extend our understanding of the evolved human life history by illustrating how changes in embodied capital and the needs of dependent offspring predict the development of men's and women's ethnobiological knowledge across the lifespan.

Morphometry and meristics of two species of Ictalurus (Siluriformes: Ictaluridae), native catfishes of Sierra Madre Occidental, Mexico

Introduction: Morphotypes of native catfish of the genus Ictalurus (Siluriformes: Ictaluridae) are known to occur in allopatry in the northern Sierra Madre Occidental of Mexico, with only the Yaqui catfish (Ictalurus pricei) taxonomically described. Recent genetic analysis of these morphotypes has revealed the monophyly of the I. pricei complex, which indicates Ictalurus sp. from the Culiacán River and San Lorenzo River basins as its nearest genetic relative and recognizes as an evolutionarily significant unit the Culiacán River and San Lorenzo River morphotypes. Objective: To compare the meristic and morphometric characteristics of the catfish of the Culiacán River basin with its nearest genetic relative, the Yaqui catfish, in order to determine the presence of distinctive morphological characters that support genetic evidence previously reported for these morphotypes. Methods: Catfish specimens were collected during various field expeditions (1990-2012) to remote sites of the Sierra Madre Occidental and conducted in the Yaqui River and Culiacán River basins with the purpose of morphological comparison. Forty-five morphological characters (40 morphometric and five meristic) were examined in 76 adult specimens - 52 Ictalurus sp. and 24 Ictalurus pricei. Three groups were subject to a discriminant function analysis (DFA), including two Ictalurus sp. groups from the Humaya River and Tamazula River sub-basins, representing the Culiacán River basin, and one I. pricei group representing the Yaqui River basin. The standardized measurements and meristic data of the catfish morphotypes were compared by means of DFA. Results: The DFA revealed 12 characters to be significantly different (P< 0.01) among the groups compared. The morphological characters separating the Ictalurus sp. (Culiacán River basin) from the Yaqui catfish were associated with lower anal, pelvic and pectoral fin ray numbers, shorter head and predorsal lengths, shorter longest lateral barbel and longest dorsal ray lengths and a narrower premaxilar dentary plate; and finally longer distances in Ictalurus sp. for dorsal-fin origin to last anal-fin ray base and dorsal-fin origin to posterior end of the adipose fin base. The standardized coefficients for canonical variables 1 and 2 accounted for 85.6 % and 14.4 % of the total variation, respectively. Conclusions: The distinctive morphological characters of the Ictalurus sp. found in the Culiacán River basin, combined with the known mitochondrial evidence for this morphotype, identify it as an evolutionarily significant unit that requires description as a new species based on taxonomical protocols.

Introducción: Morfotipos de bagres nativos del género Ictalurus (Siluriformes: Ictaluridae) se distribuyen de manera alopátrica en el norte de la Sierra Madre Occidental, de los cuales solo el bagre Yaqui (Ictalurus pricei) ha sido taxonómicamente descrito. Análisis genéticos recientes de esos morfotipos han revelado la monofilia del complejo I. pricei, que incluyó a Ictalurus sp. de las cuencas de los ríos Culiacán y San Lorenzo como su pariente genético más cercano, además del reconocimiento de los morfotipos de los ríos Culiacán and San Lorenzo como una unidad evolutivamente significativa. Objetivo: Comparar características merísticas y morfométricas del bagre de la cuenca del río Culiacán con su pariente genético más cercano, el bagre Yaqui, con el propósito de determinar la presencia de caracteres morfológicos distintivos en apoyo a evidencia genética previamente reportada para esos morfotipos. Métodos: Especímenes de bagres fueron recolectados durante varias expediciones de campo (1990-2012) en sitios remotos de la Sierra Madre Occidental en las cuencas de los ríos Yaqui y Culiacán para comparación morfológica. Cuarenta y cinco caracteres morfológicos (40 morfométricos y cinco merísticos) fueron examinados en 76 especímenes adultos (52 de Ictalurus sp. y 24 de Ictalurus pricei). Medidas corporales estandarizadas y datos merísticos de los morfotipos de bagres estudiados fueron comparados por medio de un análisis de función discriminante (AFD). Resultados: El AFD arrojó 12 caracteres significativamente diferentes (P< 0.01) entre los grupos comparados. Los caracteres morfológicos que distinguen al bagre del río Culiacán del bagre Yaqui, estuvieron asociados con un menor número de radios anales, pélvicos y pectorales, así como dimensiones más pequeñas para la longitud de la cabeza, longitud predorsal, longitud de la barbilla lateral más larga, longitud del radio dorsal más largo y una menor anchura de la placa dentaria premaxilar; y finalmente, dimensiones mayores en Ictalurus sp. (cuenca del río Culiacán) para distancias como origen de aleta dorsal a la base del último radio anal y origen de aleta dorsal a conexión posterior de aleta adiposa. Los coeficientes estandarizados para las variables canónicas 1 y 2 explicaron el 85.6 y 14.4 % de la variación total, respectivamente. Conclusiones: Los caracteres morfológicos distintivos de Ictalurus sp. de la cuenca del río Culiacán, en combinación con la evidencia mitocondrial conocida para este mismo morfotipo, permite reconocerlo como una unidad evolutivamente significativa y que requiere ser descrita como una especie nueva bajo los protocolos taxonómicos.

Edad y crecimiento del pez Fundulus lima (Cyprinodontiformes: Fundulidae) en el río La Purísima, Baja California Sur, México

Introducción: El estudio de la edad y crecimiento en peces es un prerrequisto básico para generar información sobre la longevidad, tasas de crecimiento y estructura poblacional, entre otros atributos, todos ellos para la aplicación de políticas enfocadas en el manejo y conservación poblacional. Evaluamos estos atributos en la sardinilla peninsular en peligro de extinción (Fundulus lima) que habita los oasis de Baja California Sur, con la perspectiva de generar información base de este pez endémico. Objetivo: Determinar la edad, crecimiento somático y estructura de las poblaciones de F. lima en una de las cuencas hidrológicas más importantes de su ámbito de distribución. Métodos: De octubre 2002 a julio 2004 se muestreó F. lima en 4 sitios del río La Purísima por métodos de captura pasiva y activa. Los individuos fueron medidos y pesados en el campo, donde submuestras fueron seleccionadas para el análisis de la edad en escamas. Todos los individuos fueron liberados vivos a sus sitios originales de captura. Estimamos edad, relaciones longitud-peso y longitud-longitud, y estructura poblacional, basados en 802 individuos examinados por técnicas no invasivas. Resultados: El crecimiento somático de F. lima fue alométrico positivo (b > 3.0) en todas las poblaciones estudiadas, con valores de "b" variando de 3.126 (Ojo de Agua) a 3.420 (El Pilón). Tres clases de edad (0, 1 y 2 años) fueron reconocidas, de las cuales la edad 1 fue la más frecuente (49 %). El método polimodal basado en datos de frecuencia de tallas identificó tres clases de edad. Longitudes totales retrocalculadas en edades previas basadas en incrementos de crecimiento en escamas fue entre 38.61 y 68.81 mm para individuos de 1 y 2 años, respectivamente. Conclusiones: Tres clases de edad (0, 1 y 2 años) fueron determinadas para las poblaciones de F. lima en el río La Purísima, basadas en la interpretación de anillos de crecimiento anual en escamas y en la distribución modal de frecuencia de tallas observadas. Todas las poblaciones examinadas demostraron un crecimiento alométrico positivo (b > 3.0).

Introduction: The study of age and growth in fishes is a basic prerequiste to generate information on longevity, growth rates, population structure, among other attributes, all of them for the application of policies focused on the population management and conservation. We evaluated these attributes in the endangered Baja California killifish (Fundulus lima) that inhabits the oases of Baja California Sur, Mexico, with the perspective of generating base information for the conservation of this endemic fish. Objective: To determine the age, somatic growth and population structure of F. lima in one of the most important hydrological basins of its distribution range. Methods: From October 2002 to July 2004 we sampled for F. lima in 4 sites of La Purisima river by using passive and active collection methods. Individuals were measured and weighed in the field, where subsamples were selected for analysis of age based on scales. All of the individuals were released alive to its original sites of capture. We assessed the age, length-weight and length-length relationships and population structure on the basis of 802 individuals examined by non-invasive techniques. Results: The somatic growth of F. lima was of positive allometric type (b > 3.0) in all the populations studied, with values of "b" ranging from 3.126 (Ojo de Agua) to 3.420 (El Pilón). Three age class (0, 1 and 2 years old) were recognized, of which the age 1 year was the most frequent (49 %). The polimodal method based on length-frequency data also identified three age classes. Back-calculated total lengths at previous ages based in increments of growth in scales were 38.61 and 68.81 mm for individuals of 1 and 2 years, respectively. Conclusions: Three age classes (0, 1 and 2 years old) were determined for the populations of F. lima in La Purisima river, based on the interpretation of annual growth rings in scales and in the modal distribution of observed length frequencies. All the populations examined showed a positive allometric growth (b > 3.0).

Composición taxonómica y abundancia espacio-temporal de la ictiofauna del Río Presidio, Sinaloa, México / Taxonomic composition and spatio-temporal abundance of the ichthyofauna in Presidio River, Sinaloa, Mexico

Resumen El Río Presidio, ubicado en el sur de Sinaloa, México, pertenece a la zona de transición zoogeográfica NeárticoNeotropical, donde su fauna de peces podría manifestar cambios en la abundancia y distribución de las especies durante los períodos de lluvias y de secas. El objetivo principal de este estudio fue describir la composición taxonómica y la abundancia espacial y temporal de la fauna de peces de la parte baja y media del Río Presidio, mediante muestreos bimestrales de abril 2008 a febrero 2009. Cuarenta especies (39 nativas y 1 exótica) pertenecientes a 32 géneros y 19 familias fueron registradas, siendo las familias Gerreidae y Poeciliidae las más diversas con cinco y cuatro especies, respectivamente. Seis especies: Lile stolifera, Oreochromis aureus, Awaous banana, Gobiomorus maculatus, Anchoa analis y Atherinella crystallina, en ese orden de importancia contribuyeron con casi el 49 % de la abundancia íctica total. La riqueza de especies y la salinidad demostraron una relación directa y ambas tuvieron una relación inversa con la altitud. Con base en la disimilitud de especies entre sitios, dos tipos de ensambles de peces fueron distinguidos a través de un gradiente de salinidad y turbidez en el río, el primero representado por especies de derivación marina (periféricas) en la parte baja, y el segundo por especies dulceacuícolas secundarias en la parte media. La mayor similitud de especies se dio en agosto y septiembre y estuvo asociada a condiciones de altos flujos del periodo de lluvias. Veintisiete especies tienen afinidad a la Región del Pacífico oriental, seis a la Región Neotropical, dos a la Región Neártica (Dorosoma smithi e Ictalurus cf. pricei), una Anfiatlántica (Mugil curema), una Circumtropical (M. cephalus), dos Anfiamericanas (Agonostomus monticola y Gerres cinereus) y una exótica (O. aureus).

Abstract The Rio Presidio in the southern Sinaloa, Mexico belongs to Nearctic-Neotropical zoogeographical transition zone, where its fish fauna could manifest changes in the abundance and distribution of the species during rainy and dry periods. The main objective of this study was to describe the taxonomic composition and spatial and temporal abundance of the fish fauna from the lower and middle Rio Presidio, by means of bimonthly samplings from April 2008 to February 2009. Forty fish species (39 native and 1 exotic) belonging to 32 genera and 19 families were registered. Two families (Gerreidae and Poeciliidae) contained the highest numbers of species (five and four, respectively). Six species (Lile stolifera, Oreochromis aureus, Awaous banana, Anchoa analis, Gobiomorus maculatus and Atherinella crystallina) in this order of importance contributed with almost 49 % of the total fish abundance. Species richness and salinity showed a direct relationship and an inverse relationship with the altitude. Based on the coefficient of similarity of species among sites two fish assemblages were identified. The first assemblage formed by species from marine derivation (peripheral) occurring in the lower part of the river, and the second assemblage by secondary freshwater species in the middle part. The higher fish species similarity observed in August and September was under the influence of the highest flows of the rainy period. Twenty-seven 27 species showed affinity to the Tropical Eastern Pacific Region, six species to the Neotropical region and two to the Nearctic region (Dorosoma smithi and Ictalurus cf. pricei ); one species has an Amphiatlantic distribution (Mugil curema), another is circumtropical (Mugil cephalus), two species have Amphiamerican distribution (A. monticola and G. cinereus), and one is exotic (O. aureus). Rev. Biol. Trop. 66(2): 848-862. Epub 2018 June 01.

Genotoxic Assessment of Some Inorganic Compounds in Desert Pupfish (Cyprinodon macularius) in the Evaporation Pond from a Geothermal Plant.

The frequency of micro nucleated erythrocytes in peripheral blood of the desert pupfish (Cyprinodon macularius) from a geothermal effluent pond is determined and compared to organisms kept in an aquarium. The frequency of micronucleated erythrocytes found in pupfish from the geothermal pond is 2.75 (±2.09) and only 0.44 (±0.52) in captivity organisms. Dissolved As in the ponds doubles the 340 µg L-1 US-EPA acute quality criteria for aquatic life and Hg equals the 1.77 µg L-1 chronic criteria. The organisms with high MNE also have significantly high Se, As and Hg concentrations in muscle and liver. Compared to international maximum allowable limits for fish consumption, there is 81× enrichment for Se, 6× for As and 5× for Hg. Although Se is not significantly enriched in water, it is likely that its bioaccumulation occurs via feeding of detritus. The desert pupfish has a significant resistance to extreme metal accumulations and to recover under unpolluted conditions.

Assessing population-level morphometric variation of the Mountain Mullet Agonostomus monticola (Teleostei: Mugilidae) across its Middle American distribution

Population-level morphometric variation of the Mountain Mullet (Agonostomus monticola) was assessed in 419 adult specimens from 25 sample sites (river basins) across its Middle American distribution (Pacific and Atlantic-Caribbean drainages). This analysis was based on 36 standardized linear measurements and 19 landmarks on geometric morphometrics approach. Discriminant function analysis (DFA) revealed 19 linear morphological characters with significant variation among groups. Geometrically, the most notable changes were associated to the curvature of the frontal region of the head, the anterior and posterior insertion of the first dorsal and anal fins. The resulting grouping based on the DFA and geometric morphometrics techniques (Pacific-A, Pacific-B and NE México-Caribbean) were similar to those previously recovered by genetic techniques, where the Pacific-B (Ayuquila river basin) was the most different group. Our results provide morphological evidence for considering Agonostomus monticola as a complex of evolutionary entities, represented by two forms in the Pacific Ocean and another in the Atlantic Ocean.(AU)

La variación morfométrica de poblaciones de la lisa de montaña Agonostomus monticola fue evaluada en 419 especímenes adultos recolectados en 25 sitios (cuencas) a través de su distribución mesoamericana (Pacífico, Atlántico y cuencas del Caribe). El análisis fue basado en 36 medidas lineales estandarizadas y 19 puntos de referencia basados en morfometría geométrica. El análisis de función discriminante (AFD) reveló 19 caracteres morfométricos con variación significativa entre grupos. Geométricamente, los cambios más notables estuvieron asociados con la curvatura de la región frontal de la cabeza y la inserción anterior y posterior de la primera aleta dorsal y de la aleta anal. Los agrupamientos resultantes del AFD y del análisis de morfometría geométrica (Pacífico-A, Pacífico-B y NE México-Caribe) fueron similares con los previamente definidos mediante técnicas genéticas. El grupo Pacífico-B (cuenca de Ayuquila) fue el más disímil. Nuestros resultados proveen evidencia morfológica para considerar a Agonostomus monticola como un complejo de entidades evolutivas, representadas por dos formas en la cuenca del océano Pacífico y una forma en la cuenca del océano Atlántico.(AU)

Complete mitochondrial genome of Ictalurus pricei (Teleostei: Ictaluridae) and evidence of a cryptic Ictalurus species in Northwest Mexico.

The nominal Yaqui catfish, Ictalurus pricei, is a species of Ictaluridae (Siluriformes) often recorded from Northwest Mexico. Southern distribution members of the I. pricei complex in Northwest Mexico include at least one undescribed species that differs from Yaqui catfish in morphological features, herein called "Sinaloa Catfish". Sequencing of four geographical mitogenome haplotypes of Yaqui catfish and Sinaloa catfish showed geographical haplotypes of I. pricei within a clade of specific identity, close to Sinaloa catfish haplotypes. Our molecular phylogeny represents a working hypothesis supporting information on the evolutionary relationships of the Ictalurus species from Western Mexico and Western USA.

Entire mitochondrion genome sequence of the Desert Pupfish, Cyprinodon macularius Baird & Girard, 1853.

The complete mitochondrial genome sequence of the Desert Pupfish, Cyprinodon macularius (Gene accession number KM985373) has a length of 16,940 bp, and the arrangement consisted of 13 protein-coding genes, 2 ribosomal RNA (rRNA) genes and 22 transfer RNA, which are similar to other known mitogenomes for the family Cyprinodontidae.

El hueso urohial de los peces gerreidae (Teleostei: Percoidei) de américa y su aplicación taxonómica / The urohyal bone of the american gerreidae (Teleostei: Percoidei) and its taxonomic application

El urohial es un hueso impar de origen dérmico, ubicado en el centro de la mandibula inferior de los peces teleósteos y constiyuye un elemento fundamental en el mecanismo de apertura bucal. El estudio comparativo del hueso urohial en los Gerreidae americanos, sustenta la idea de que dicha estructura manifesta formas distintivas que pudieran ser de gran utilidad para la diferenciación taxonómica a nivel de géneros y de especies. La presente contribución ofrece una descripción de las características que distinguen la morfología del hueso urohial de cinco especies selectas representativas de cuatro géneros de la familia Gerreidae en América: Diapterus (D. brevirostris), Eucinostomus (E. dowii), Eugerres (E. lineatus y E. mexicanus) y Gerres (G. cinereus).

The urohyal is a single bone of dermal origin, located in the center of the lower jaw bones of teleostean fishes, which represents the original point for the function of the mouth-opening mechanism. The comparative study of the urohyal morphology in American gerreids supports the idea that this bony structure shows different forms that might be of great usefulness for the taxonomic discrimination among genera, and even species. This study provides the description of morphological characteristicas of the urohyal bone, that allows these to be distinguished among five selected species representatives of four genera of American gerreids: Diapterus (D. brevirostris), Eucinostomus (E. dowii), Eugerres (E. lineatus and E. mexicanus) and Gerres (G. cinereus).

Seasonal diet composition of Fundulus lima (Cyprinodontiformes: Fundulidae) in two oasis systems of Baja California Sur, Mexico

Fundulus lima inhabits river drainage systems and is threatened after the introduction of cichlids in the area. To support conservation programs, the spatial and temporal variation of the diet composition of this endangered killifish, was determined in two oasis systems of Baja California Sur, Mexico (San Ignacio and La Purisima river drainages), during rainy and dry seasons. F. lima was captured by using passive and active capture techniques. A total of 192 stomach contents of F. lima was analyzed. The contribution of each prey item in the diet composition was quantified by means of the indices of occurrence frequency (% OF), numerical (%N) and volume (%V) percentages. The relative importance of each prey item was determined according to the percentage of the Relative Importance Index (%RII). The similarity of the diet was calculated between hydrological basins (populations combined by basin), seasons (rainy versus dry months), sexes and size classes, by using Schoener’s resource overlap index. We used two ecological indices to determine the type of feeding strategy exhibited by the fish: (1) niche breadth of Levins and (2) proportional similarity of Feisinger. Sand was the most abundant item in the stomach content of killifishes from both drainages (39% and 47%, respectively). Diet composition was similar for both drainages (74%) as well as among their respective size classes; however, it was different between sexes. In both drainages, F. lima predated mainly on diatom algae, dipterous and trichopteran larvae, and fish scales during the dry season; while it preferred dipterous larvae, filamentous algae and ostracods in the rainy season. A feeding strategy of opportunist type was exhibited by F. lima during the rainy season, changing to specialist type during the dry season. This information will be the basis for future investigations related to the conservation of this endangered species and its habitat. Rev. Biol. Trop. 59 (4): 1669-1678. ...

Fundulus lima habita sistemas de aguas continentales, y se encuentra amenazado tras la introducción de cíclidos en el área de estudio. Para poder llevar a cabo programas de conservación, fue determinada la dieta de la sardinilla peninsular en peligro de extinción, en dos sistemas de oasis de Baja California Sur, México (cuencas de los rios San Ignacio y La Purísima), durante las épocas secas y de lluvias. Una gran proporción de arena fue encontrada en el contenido estomacal de este pez para ambas cuencas (39% y 47%, respectivamente). La composición de la dieta fue similar entre ambas cuencas (74%), como también dentro de sus respectivas clases de tallas; sin embargo, fue diferente entre sexos. Durante la época de secas, F. lima consumió principalmente diatomeas, larvas de dípteros y tricópteros, además de escamas de peces; mientras que en la época de lluvias tuvo preferencia por las larvas de dípteros, algas filamentosas y ostrácodos. Este pez exhibe una estrategia alimentaria de tipo oportunista durante la época de lluvias, la cual cambia a tipo especialista en la época de secas. Esta información será la base para futuras investigaciones relacionadas con la conservación de esta especie, en peligro de extinción, y su hábitat.

Seasonal diet composition of Fundulus lima (Cyprinodontiformes: Fundulidae) in two oasis systems of Baja California Sur, Mexico.

Fundulus lima inhabits river drainage systems and is threatened after the introduction of cichlids in the area. To support conservation programs, the spatial and temporal variation of the diet composition of this endangered killifish, was determined in two oasis systems of Baja California Sur, Mexico (San Ignacio and La Purisima river drainages), during rainy and dry seasons. F. lima was captured by using passive and active capture techniques. A total of 192 stomach contents of F. lima was analyzed. The contribution of each prey item in the diet composition was quantified by means of the indices of occurrence frequency (% OF), numerical (% N) and volume (% V) percentages. The relative importance of each prey item was determined according to the percentage of the Relative Importance Index (% RII). The similarity of the diet was calculated between hydrological basins (populations combined by basin), seasons (rainy versus dry months), sexes and size classes, by using Schoener's resource overlap index. We used two ecological indices to determine the type of feeding strategy exhibited by the fish: (1) niche breadth of Levins and (2) proportional similarity of Feisinger. Sand was the most abundant item in the stomach content of killifishes from both drainages (39% and 47%, respectively). Diet composition was similar for both drainages (74%) as well as among their respective size classes; however, it was different between sexes. In both drainages, F. lima predated mainly on diatom algae, dipterous and trichopteran larvae, and fish scales during the dry season; while it preferred dipterous larvae, filamentous algae and ostracods in the rainy season. A feeding strategy of opportunist type was exhibited by F. lima during the rainy season, changing to specialist type during the dry season. This information will be the basis for future investigations related to the conservation of this endangered species and its habitat.