Comparative analysis of the diet composition and its relation to morphological characteristics in Achirus mazatlanus and Syacium ovale (Pleuronectiformes: Osteichthyes) from a Mexican Pacific coastal lagoon

The purpose of this research was to investigate differences in diet composition between Achirus mazatlanus and Syacium ovale, two flatfishes inhabiting in a tropical coastal lagoon and to investigate the relationship of their feeding habits to size, body morphometry and mouths characteristics. Fish were collected during sampling trips conducted regularly from 2011 to 2016 using several types of fishing gear. Total number of analyzed stomachs with some food content was 328 for Achirus mazatlanus from 1.4 to 21.3 cm total length (TL) and 203 for Syacium ovale with 1.3 to 24.0 cm TL. Results indicate that both species share a general diet based on benthic invertebrates and fishes but S. ovale has a more piscivorous habit, which can be explained by a more slender body shape and larger teeth, characteristics which increase prey fish catching performance. Important changes in composition of food categories related to size were not found for any species, but larger fish of both species eat larger ranges of prey sizes, and this ontogenetic change is consistent with recent developments on optimal foraging theory.(AU)

Se investigaron las diferencias en la composición de la dieta entre Achirus mazatlanus y Syacium ovale, dos especies de lenguados que habitan en una laguna costera tropical, y la relación de los hábitos alimentarios con el largo total, la morfometría corporal y las características de las bocas. Los peces fueron colectados regularmente entre 2011 y 2016, mediante varios tipos de artes de pesca diferentes. El número total de estómagos analizados con contenido estomacal fue de 328 para Achirus mazatlanus de 1.4 a 21.3 cm de longitud total (TL) y 203 para Syacium ovale de 1.3 a 24.0 cm TL. Los resultados indican que ambas especies tienen una dieta general basada en invertebrados bentónicos y peces, pero S. ovale tiene un hábito más piscívoro, lo cual puede ser explicado por un cuerpo más alargado y dientes más grandes, características ambas que incrementan el rendimiento de la captura de peces presas. No se encontraron cambios importantes en la composición de las categorías alimentarias relacionados con la talla en ninguna de las especies de lenguados, pero los peces mayores de ambas especies consumen rangos más amplios de tamaños de presas y este cambio ontogénico es consistente con la teoría de forrajeo óptimo.(AU)

External morphology, postcranial and appendicular osteology of three southwestern Atlantic flatfishes ( Paralichthys, Paralichthyidae), and comparisons with other congeneric species

Comparisons of the external morphology and analysis of osteological features of the postcranial and appendicular skeletons of three southwestern Atlantic flatfish species of the genus Paralichthys (P. isosceles, P. orbignyanus and P. patagonicus) were carried out. Bones are described, and detailed morphological, morphometric and meristic characteristics of these flounders are given in order to provide information about the external and internal morphology of three species of Paralichthys occurring in the south-west Atlantic waters that add new information and will help regarding within the framework of a phylogenetic study of the group. Interspecific differences were found in the number of vertebrae and intermuscular bones, as well as in the morphology and morphometry of vertebrae, caudal skeletons, pectoral and pelvic girdle bones. Relationships between bones are discussed and bone characteristics compared with those found in other species of Paralichthys and in other pleuronectiform species. The position of Paralichthys isosceles within Paralichthys is discussed, along with other congeners such as P. triocellatus and P. oblongus.(AU)

Se llevaron a cabo comparaciones de la morfología externa y el análisis de las características osteológicas de los esqueletos postcraneal y apendicular de tres especies de peces planos del Atlántico sudoccidental del género Paralichthys (P. isosceles, P. orbignyanus y P. patagonicus). Se describen los huesos, y se proporcionan características morfológicas, morfométricas y merísticas detalladas de estos lenguados con el fin de aportar información sobre la morfología externa e interna de tres especies de Paralichthys presentes en el Atlántico sudoccidental. Esta nueva información contribuirá al marco de un estudio filogenético del grupo. Se encontraron diferencias interespecíficas en el número de vértebras y huesos intermusculares, así como en la morfología y morfometría de las vértebras, los esqueletos caudales, los huesos de las cinturas pectoral y pélvica. Se discuten las relaciones entre los huesos y las características óseas en comparación con las encontradas en otras especies de Paralichthys y de otros Pleuronectiformes. Se discute la posición de Paralichthys isosceles dentro del género Paralichthys, junto con otros congéneres como P. oblongus y P. triocellatus.(AU)

Osteología comparada del esqueleto caudal de Achirus lineatus y Achirus mazatlanus (Pleuronectiformes: Achiridae) / Comparative osteology of the caudal skeleton of Achirus lineatus and Achirus mazatlanus (Pleuronectiformes: Achiridae)

El esqueleto caudal constituye una importante herramienta para evaluar las relaciones ancestro-descendencia de los peces teleósteos. Por tal motivo, se realizó un análisis osteológico comparativo de dicha estructura, a partir de ejemplares de las especies Achirus lineatus (Linnaeus, 1758) y A. mazatlanus (Steindachner, 1869), obtenidos de colecciones científicas de referencia y recolectados in situ en Veracruz y Baja California Sur (México). Los organismos fueron identificados con claves taxonómicas especializadas y procesados mediante la técnica de aclaración y tinción diferencial, para evaluar las posibles similitudes o diferencias en las estructuras que componen al complejo caudal. Achirus lineatus y A. mazatlanus se caracterizan por la presencia de una fórmula caudal compuesta por 1 epural + 5 hipurales + 1 parahipural, además de una espina neural y dos espinas hemales; así como por la presencia de 16 radios principales y la ausencia de los radios procurrentes y el uroneural. Asimismo, se observo que en la especie A. lineatus, los hipurales se encuentran más cercanos uno del otro; sin embargo, en lo general, no se aprecio una clara diferencia en los elementos que componen la aleta caudal de las especies bajo estudio. Por consiguiente A. lineatus y A. mazatlanus son consideradas como especies fraternas.

The caudal skeleton is recognized as an important source of information for establishment of teleostean interrelationships. A comparative analysis of the caudal skeleton of Achirus lineatus (Linnaeus, 1758) and A. mazatlanus (Steindachner, 1869) was performed, based on the examination of specimens from biological museums and others materials collected in Veracruz localities and Baja California Sur (Mexico). The specimens were identified using taxonomic keys and processed by means of clearing and staining methods, in order to determine the differences and similarities on the elements that characterized the caudal complex of this species. The caudal formula in A. lineatus and A. mazatlanus is composed by: 1 epural + 5 hypurals + 1 parhypural, one neural and two hemal spines, as well as the presence of 16 principal rays and absence of procurrent rays and the uroneural bone. The hypural in the A. lineatus are closer together; however, in general, differences were not observed among the species. Therefore, A. lineatus and A. mazatlanus are established as sister species.

Growth and mortality of the fish Citharichthys xanthostigma (Pleuronectiformes: Paralichthyidae) off the Western coast of Baja California, México

Longfin sanddab (Citharichthys xanthostigma) represents a very important fishery resource in Southern and Baja California but are not very well known. The purpose of this study is to provide information on the growth and mortality of longfin sanddab population in the Mexican Pacific Ocean at Baja California, México. Data on growth were obtained for longfin sanddab collected with otter trawls during six cruises off the Western coast of Baja California. A total of 1 017 longfin sanddab were caught over the sampling period, and from 860 specimens, the male to female ratio was 1:1.8. The relationship between total weight (W) and standard length (SL) is described: W=0.00000743 SL3.196 for females and W=0.00000764 SL3.193 for males. Age groups were estimated from length frequency data, and von Bertalanffy annual growth parameters for all fish data combined were the following: L∞=289.2mm SL, k=0.20, t0=-0.73; for males, they were L∞=265.9mm SL, k=0.21, t0=-0.68, and for females, L∞=293.6mm SL, k=0.23, t0=-0.35. Longfin sanddab caught during this study reached a maximum age of 10 years, and at that age, males attained smaller sizes than females. The age groups had a total mortality (Z) rate of 0.82 year-1, a fishing mortality (F) of 0.52 year-1, and a natural mortality (M) of 0.3 year-1. Although the longfin sanddab is not a target species of commercial fisheries, it suffers high mortality as part of the bycatch in the shrimp fishery. Rev. Biol. Trop. 58 (2): 689-705. Epub 2010 June 02.

Se presenta información sobre el crecimiento y mortalidad de la población del C. xanthostigma (lenguado alón) en el Pacífico Mexicano de Baja California, México. Datos sobre su crecimiento fueron obtenidos de peces capturados con red de arrastre durante seis cruceros en la costa Oeste de Baja California, México. Se capturaron 1 017 peces en este periodo. La relación machos:hembras de 860 ejemplares fue de 1:1.2. La relación peso total (W) y longitud estándar (SL) se estimó para hembras: W=0.00000743 SL 3.196 y para machos: W=0.00000764 SL 3.193. La edad de los grupos se calculó con datos de frecuencia por longitud, el crecimiento de von Bertalanffy global fue: L∞=289.2mm SL, k=0.20, t0= -0.73; para los machos: L∞=265.9 mm SL, k=0.21, t0= -0.68 y para las hembras: L∞=293.6mm SL, k=0.23, t0=-0.35, anualmente. La captura de C. xanthostigma durante este estudio alcanzó una edad máxima de 10 años. Los machos alcanzan tallas menores que las hembras a la misma edad. Los grupos de edad tuvieron una tasa de mortalidad total (Z) de 0.82 por año, una mortalidad por pesca (F) de 0.52 por año y mortalidad natural (M) de 0.3 por año. Aunque el C. xanthostigma no es una especie objetivo (comercial), sufre una alta mortalidad indirecta durante la pesca del camarón.

Redescription of Symphurus diabolicus, a poorly-known, deep-sea tonguefish (Pleuronectiformes: Cynoglossidae) from the Galápagos Archipelago

Symphurus diabolicus, previously known only from the holotype collected in 501 m west of Isla San Cristobal (Chatham Island), Galápagos Archipelago, is re-described based on the holotype (112.6 mm SL) and 19 additional specimens (61.1-123.5 mm SL) recently collected from deep waters around the Galápagos Archipelago. Symphurus diabolicus is characterized by: an elongate body; narrow head with pointed snout; 1-3-2 ID pattern; 106-110 dorsal-fin rays; 89-96 anal-fin rays; 12 caudal-fin rays; 57-59 total vertebrae; 5 hypurals; extremely small scales; no pupillary operculum; large, prominent eyes, with migrated eye near dorsal margin of head; relatively short postorbital head length; relatively long snout and predorsal lengths; black peritoneum visible through abdominal wall on both sides of body; uniform olive green to dark brown ocular-side coloration with series of prominent, darker brown, elliptical to rectangular, blotches (not usually forming crossbands) along body at bases of dorsal and anal fins; and uniformly whitish or light yellow blind side. Symphurus diabolicus appears to be endemic to the Galápagos Archipelago, and is relatively common (captured at 16 different localities) at depths of 308 to 757 m (observed as shallow as 245 m) in this region. Examination of this expanded series of specimens confirms the validity of S. diabolicus and provides characters to distinguish it from S. microlepis Garman, a similar species known only from the holotype taken at approximately 530 m off Pacific Panama.

A new species of Trinectes (Pleuronectiformes: Achiridae), with comments on the other eastern Pacific species of the genus

A new eastern Pacific achirid, Trinectes xanthurus, has a distinctive yellow or light caudal fin, without pattern, to contrast with its relatively dark body. This species also has black, posterior margins of the dorsal and anal fins and 21-22 caudal vertebrae, versus 19-20 for its Pacific coast congeners. It usually is found in shallow, continental shelf waters on sand or mud bottoms and ranges from Colombia to El Salvador. The genus Trinectes is represented in the eastern Pacific by four species. A fifth species usually occurs in Pacific slope drainages (freshwater) in Panama. Of these species, only Trinectes fonsecensis is found throughout the tropical eastern Pacific, while the other three coastal species are confined to tropical waters south of the Golfo de Tehauntepec.