Areas de migración y ecología de la anchoa Lycengraulis olidus (Günther) en las aguas argentinas (Pisces, fam. Engraulidae)

The purpose of the present study was to confirm the migratory habits of the anchovy, Lycengraulis olidus (Günther), between fresh and sea water environments. Anchovies were examined from three freshwater localities: Bella Vista and Rosario (Paraná river) and Punta Lara (La Plata river), and from four marine localities; Mar del Plata, Bahia Blanca, San Blas and Patagones, all in the Argentine Republic. Five meristic and nine morphometric characters were selected for study, namely: vertebrae; dorsal, pectoral and anal fin rays; gill rakers on the first gill arch; head-length; body-depth; distance between the snout and dorsal, pectoral, ventral and anal fin; eye-diameter; snout and maxilary. The food of the anchovy in fresh and sea water consists principally of fish and crustaceans including copepods, paleamonids, sergestids and larvae of Brachyura. The condition factor of the anchovy was lower in the fresh-water samples and higher in the marine samples. (PDF has 32 pages (two pages on each)

Field guide to requiem sharks (Elasmobranchiomorphi: Carcharhinidae) of the Western North Atlantic

Identification problems are common for many sharks due to a general lack of meristic characteristics that are typically useful for separating species. Other than number of vertebrae and number and shape of teeth, identifications are frequently based on external features that are often shared among species. Identification problems in the field are most prevalent when live specimens are captured and releasing them with a minimum of stress is a priority (e.g., shark tagging programs). Identifications must be accurate and conducted quickly but this can be challenging, especially if specimens are very active or too large to be landed without physical damage. This field guide was designed primarily for use during field studies and presents a simplified method for identifying the 21 species of western North Atlantic Ocean sharks belonging to the family Carcharhinidae (carcharhinids). To assist with identifications a dichotomous key to Carcharhinidae was developed, and for the more problematic Carcharhinus species (12 species), separation sheets based on important distinguishing features were constructed. Descriptive text and illustrations provided in the species accounts were developed from field observations, photographs, and published references. (PDF file contains 36 pages.)

Guide to the Identification of Larval and Early Juvenile Poachers (Scorpaeniformes: Agonidae) from the Northeastern Pacific Ocean and Bering Sea

Developmental stages of 22 species representing 16 genera of agonid fishes occurring in the northeastern Pacific Ocean from San Francisco Bay to the Arctic Ocean are presented. Three of these species also occur in the North Atlantic Ocean. Larval stages of nine species are described for the first time. Additional information or illustrations intended to augment original descriptions are provided for eight species. Information on five other species is provided from the literature for comparative purposes. The primary objective of this guide is to present taxonomic characters to help identify the early life history stages of agonid fishes in field collections. Meristic, morphometric, osteological, and pigmentation characters are used to identify agonid larvae. Meristic features include numbers of median-fin elements, pectoral-fin rays, dermal plates, and vertebrae. Eye diameter, body depth at the pectoral-fin origin, snout to first dorsal-fin length, and pectoral-fin length are the most useful morphological characters. Presence, absence, numbers, and/or patterns of dermal plates in lateral rows or on the ventral surface of the gut are also useful. Other important characters are the presence, absence, numbers, and ornamentation of larval head spines. Lastly, distinct pigmentation patterns are often diagnostic. The potential utility of larval characters in phylogenetic analysis of the family Agonidae is discussed. (PDF file contains 92 pages.)

A study of populations of the anchoveta, Cetengraulis mysticetus, based on meristic characters

ENGLISH: This study was undertaken to determine whether meristic characters indicate that more than one major population of anchovetas occurs in the range of the species from Mexico to Peru. Interest in this species lies in the fact that it is the principal bait fish used to catch yellowfin and skipjack tunas in the Eastern Pacific. Specimens examined were from collections made by California tuna fishing vessels at six major baiting localities covering nearly the entire range of the species, namely, Almejas Bay on the outer coast of Baja California, Guaymas and Ahome Point in the Gulf of California, Gulf of Fonseca, Gulf of Panama, and Gulf of Guayaquil. Four meristic characters were selected for study: vertebrae, dorsal fin rays, anal fin rays, and gill rakers on the first gill arch. Vertebral counts, using X-ray film, were taken from a total of 1,500 fish, 250 each from each of the six localities. For the other characters, 125 anchovetas were examined from each locality for a total of 750, the counts being made with the aid of a binocular microscope. Specimens were between 80 and 165 mm. standard length. SPANISH: Este estudio ha sido hecho con el propósito de determinar si los caracteres numéricos de las anchovetas indican que existe más de una población de este pez en la zona en que se encuentra la especie, comprendida entre México y Perú. El interés en dicha especie radica en el hecho de que éste es el pez de carnada usado principalmente para la pesca de los atunes "aleta amarilla" y "barrilete" en el Pacífico Oriental. Los especímenes que han sido examinados, se tomaron de las muestras recogidas por los barcos atuneros de California en seis de las mejores localidades en que se pesca la anchoveta, las cuales comprenden casi toda la zona en donde se encuentra la especie, a saber, Bahía de Almejas en la costa exterior de Baja California, Guaymas y Punta Ahorne en el Golfo de California, el Golfo de Fonseca, el Golfo de Panamá y el Golfo de Guayaquil. Cuatro caracteres numéricos fueron escogidos para su estudio: los que presentan 1) las vértebras, 2) los radios de la aleta dorsal, 3) los radios de la aleta anal y 4) las branquispinas del primer arco branquial. Mediante el uso de películas con rayos X, se contaron las vértebras en un total de 1,500 peces, es decir, 250 de cada una de las seis mencionadas localidades. En relación con los otros caracteres, se examinaron 125 anchovetas de cada área, o sea, un total de 750 ejemplares, habiendo sido hecho el conteo por medio de un microscopio binocular. Los especímenes tenían un largo standard entre 80 y 165 milímetros. (PDF contains 24 pages.)

Eggs, Larvae and Young of The Striped Bass, Roccus saxatilis

Detailed descriptions of the early development of the striped bass, Roccus saxitilis (Walbaum), with emphasis on variation in size and morphology, sequence of fin formation, changes in body form, and attainment of the full complement of maristic numbers, are presented and illustrated for the first time. The egg is spherical, transparent, non-adhesive and relatively large. It is pelagic and buoyant, although it sinks in quiet fresh water. When unfertilized, it averages 1.3 mm, in diameter, but is 3.4 mm. when fertilized and water-hardened. The granular yolk sac, green when alive and whitish-yellow when preserved, averages 1.2 mm., and the single amber-colored oil globule is about 0.6 mm. in diameter. Newly hatched striped bass prolarvae, which range from 2.9-3.7 mm. in total length, are relatively undeveloped and nearly transparent, with no mouth opening, unpigmented eyes, and a greatly enlarged yolk sac with the large oil globule projecting beyond the head. When 5-6 mm. long the yolk sac and oil globule are assimilated and the postlarvae I show advanced development of the internal anatomy. Although the fish is still transparent, scattered melanophores are found on the head and body and chromatophores in the eyes and the ventro-posterior edge of the body. Postlarvae transform to young between 7 and 10 mm. in length when the finfolds are lost except in the dorsal, anal and caudal regions. The largest fish in this group possess a well-formed skeleton with a full complement of 25 vertebrae. Between 10 and 20 mm. in length all fish are fully transformed, muscular tissue renders most of the internal structure obscure, and the myotomes, which generally correspond in number with the vertebrae, are no longer visible. At fish lengths of 20-30 mm. scales are found on all specimens, and with the exception of the pectoral fin-rays, a full complement of meristic structures is present in all other fins. At this stage the body is pigmented uniformly with small spots. Linear regressions between several dependent variables and the , independent variable of standard length indicate that the rate of development of head, eye. and snout to anus lengths is proportional to the length of the larvae and young. Body depth and standard length are non-linear among newly-hatched larvae. Hatchery-reared striped bass demonstrated a slow rate of growth, and were regarded as "stunted," when compared to growth rates observed in another study and field collections. Observations were also made on abnormal eggs and teratological larvae and young. Blue-sac disease is tentatively identified and described for the first time in larvae and pugnosed larvae and young are also described for the first time in striped bass.

Bomb radiocarbon and tag-recapture dating of sandbar shark (Carcharhinus plumbeus)

The sandbar shark (Carcharhinus plumbeus) was the cornerstone species of western North Atlantic and Gulf of Mexico large coastal shark fisheries until 2008 when they were allocated to a research-only fishery. Despite decades of fishing on this species, important life history parameters, such as age and growth, have not been well known. Some validated age and growth information exists for sandbar shark, but more comprehensive life history information is needed. The complementary application of bomb radiocarbon and tag-recapture dating was used in this study to determine valid age-estimation criteria and longevity estimates for this species. These two methods indicated that current age interpretations based on counts of growth bands in vertebrae are accurate to 10 or 12 years. Beyond these years, we could not determine with certainty when such an underestimation of age begins; however, bomb radiocarbon and tag-recapture data indicated that large adult sharks were considerably older than the estimates derived from counts of growth bands. Three adult sandbar sharks were 20 to 26 years old based on bomb radiocarbon results and were a 5- to 11-year increase over the previous age estimates for these sharks. In support of these findings, the tag-recapture data provided results that were consistent with bomb radiocarbon dating and further supported a longevity that exceeds 30 years for this species.

Age validation, growth, mortality, and demographic modeling of spotted gully shark (Triakis megalopterus) from the southeast coast of South Africa

This study documents validation of vertebral band-pair formation in spotted gully shark (Triakis megalopterus) with the use of fluorochrome injection and tagging of captive and wild sharks over a 21-year period. Growth and mortality rates of T. megalopterus were also estimated and a demographic analysis of the species was conducted. Of the 23 OTC (oxytetracycline) -marked vertebrae examined (12 from captive and 11 from wild sharks), seven vertebrae (three from captive and four from wild sharks) exhibited chelation of the OTC and fluoresced under ultraviolet light. It was concluded that a single opaque and translucent band pair was deposited annually up to at least 25 years of age, the maximum age recorded. Reader precision was assessed by using an index of average percent error calculated at 5%. No significant differences were found between male and female growth patterns (P>0.05), and von Bertalanffy growth model parameters for combined sexes were estimated to be L∞=1711.07 mm TL, k=0.11/yr and t0=–2.43 yr (n=86). Natural mortality was estimated at 0.17/yr. Age at maturity was estimated at 11 years for males and 15 years for females. Results of the demographic analysis showed that the population, in the absence of fishing mortality, was stable and not significantly different from zero and particularly sensitive to overfishing. At the current age at first capture and natural mortality rate, the fishing mortality rate required to result in negative population growth was low at F>0.004/ yr. Elasticity analysis revealed that juvenile survival was the principal factor in explaining variability in population growth rate.

Age validation of great hammerhead shark (Sphyrna mokarran), determined by bomb radiocarbon analysis

Preliminary validation of annual growth band deposition in vertebrae of great hammerhead shark (Sphyrna mokarran) was conducted by using bomb radiocarbon analysis. Adult specimens (n=2) were collected and thin sections of vertebral centra were removed for visual aging and use in radiocarbon assays. Vertebral band counts were used to estimate age, and year of formation was assigned to each growth band by subtracting estimated age from the year of capture. A total of 10 samples were extracted from growth bands and analyzed for Δ14C. Calculated Δ14C values from dated bands were compared to known-age reference chronologies, and the resulting patterns indicated annual periodicity of growth bands up to a minimum age of 42 years. Trends in Δ14C across time in individual specimens indicated that vertebral radiocarbon is conserved through time but that habitat and diet may inf luence Δ14C levels in elasmobranchs. Although the age validation reported here must be considered preliminary because of the small sample size and narrow age range of individuals sampled, it represents the first confirmation of age in S. mokarran, further illustrating the usefulness of bomb radiocarbon analysis as a tool for life history studies in elasmobranchs.

Larval development of the spotfin tonguefish (Symphurus oligomerus Mahadeva and Munroe, 1990) (Pleuronectiformes: Cynoglossidae) from the Gulf of California, Mexico

Larval and early juvenile stages of Symphurus oligomerus are described from 24 specimens from the Gulf of California. Meristic features were 48 – 49 total vertebrae, 87–94 dorsal-fin rays, 73–77 anal-fin rays, 12 caudal-fin rays, and five hypural bones. Seven larvae and one juvenile were cleared and stained to obtain the pterygiophore formula (1-3-2-2-2) that confirmed the identification of S. oligomerus. The pigment pattern from preflexion to juvenile stage consists of three bands on the dorsal margin and two bands on the ventral margin formed by star-shaped melanophores on the left side of the body. The intestine in preflexion to postflexion larvae forms an abdominal projection that ends in a short conical appendix. The intestine is supported by three cartilaginous struts; larvae with these physical attributes are called exterilium larvae. Preflexion larvae have two elongated dorsal-fin rays, and in flexion to postflexion larvae the second to the fourth dorsalfin rays are elongate. We found an apparent connection between the size at metamorphosis of the species of Symphurus and the depth distribution range of adults such that the fish species that metamorphose at a larger size have a deeper distribution as adults and exterilium larvae seem to correspond to species that have deeper distributions.

Age validation of juvenile Shortfin Mako (Isurus oxyrinchus) tagged and marked with oxytetracycline off southern California

The purpose of this study was to validate aging results of juvenile Shortfin Mako (Isurus oxyrinchus) by vertebral band counts. Vertebrae of 29 juvenile Shortfin Mako marked with oxytetracycline (OTC) were obtained from tag-recapture activities to determine centrum growth-band deposition. Tagging occurred off southern California from 1996 to 2010, and time at liberty of the 29 sharks ranged from 4 months to 4.4 years (mean=1.3 years). Growth information also was obtained from length-frequency modal analyses (MULTIFAN and MIXDIST) by using a 29-year data set of commercial and research catch data, in addition to a tag-recapture growth model (e.g, the GROTAG model). For vertebrae samples used for age validation, shark size at time of release ranged from 79 to 142 cm fork length (FL) and from 98 to 200 cm FL at recapture. Results from band counts of vertebrae distal to OTC marks indicate 2 band pairs (2 translucent and 2 opaque) are formed each year for Shortfin Mako of the size range examined. Length-frequency analyses identified 3 age class modes. Growth rate estimates from 26.5 to 35.5 cm/year were calculated for the first age-class mode (85 cm FL) and from 22.4 to 28.6 cm/year for the second age-class mode (130 cm FL). Results from the tag-recapture growth model revealed fast growth during time at liberty for tagged fish of the 2 youngest age classes. Collectively, these methods suggest rapid growth of juvenile Shortfin Mako in the southern California study area and indicate biannual deposition of growth bands in vertebrae for the first 5 years.

Larval development and identification of the genus Triglops (Scorpaeniformes: Cottidae)

Prior to Pietsch’s (1993) revision of the genus Triglops, identification of their larvae was difficult; six species co-occur in the eastern North Pacific Ocean and Bering Sea and three co-occur in the western North Atlantic Ocean. We examined larvae from collections of the Alaska Fisheries Science Center and Atlantic Reference Centre and used updated meristic data, pigment patterns, and morphological characters to identify larvae of Triglops forficatus, T. macellus, T. murrayi, T. nybelini, T. pingeli, and T. scepticus; larvae of T. metopias, T. dorothy, T. jordani, and T. xenostethus have yet to be identified and are thus not included in this paper. Larval Triglops are characterized by a high myomere count (42–54), heavy dorsolateral pigmentation on the gut, and a pointed snout. Among species co-occurring in the eastern North Pacific Ocean, T. forficatus, T. macellus, and T. pingeli larvae are distinguished from each other by meristic counts and presence or absence of a series of postanal ventral melanophores. Triglops scepticus is differentiated from other eastern North Pacific Ocean larvae by having 0–3 postanal ventral melanophores, a large eye, and a large body depth. Among species co-occurring in the western North Atlantic Ocean, T. murrayi and T. pingeli larvae are distinguished from each other by meristic counts (vertebrae, dorsal-fin rays, and anal-fin rays once formed), number of postanal ventral melanophores, and first appearance and size of head spines. Triglops nybelini is distinguished from T. murrayi and T. pingeli by a large eye, pigment on the lateral line and dorsal midline in flexion larvae, and a greater number of dorsal-fin rays and pectoral-fin rays once formed.

A remarkable new species of Psednos (Teleostei: Liparidae) from the western North Atlantic Ocean

Psednos rossi new species (Teleostei: Liparidae) is described from two specimens collected in the North Atlantic Ocean off Cape Hatteras, North Carolina, at depths of 500–674 m. Psednos rossi belongs to the P. christinae group, which includes six other species and is characterized by 46–47 vertebrae and the absence of a coronal pore. Psednos rossi differs from those six species by having characters unique within the genus: straight spine, body not humpbacked at the occiput, and a very large mouth with a vertical oral cleft. Other distinguishing characters include a notched pectoral fin with 15–16 rays, eye 17–19% SL, and color in life orange-rose. With P. rossi, the genus Psednos as currently known includes 26 described and five undescribed species of small meso- or bathypelagic liparids from the Atlantic, Pacific, and Indian Oceans.

Descriptions of larval, prejuvenile, and juvenile finescale menhaden (Brevoortia gunteri) (family Clupeidae), and comparisons to gulf menhaden (B. patronus)

Larval and juvenile development of finescale menhaden (Brevoortia gunteri) is described for the first time by using wild-caught individuals from Nueces Bay, Texas, and is compared with larval and juvenile development of co-occurring gulf menhaden (B. patronus). Meristics, morphometrics, and pigmentation patterns were examined as development proceeded. An illustrated series of finescale menhaden is presented to show changes that occurred during development. For finescale menhaden, transformation to the juvenile stage was completed by 17−19 mm standard length (SL). By contrast, transformation to the juvenile stage for gulf menhaden was not complete until 23−25 mm SL. Characteristics useful for separating larval and juvenile finescale menhaden from gulf menhaden included 1) the presence or absence of pigment at the base of the insertion of the pelvic fins; 2) the standard length at which medial predorsal pigment occurs; 3) differences in the number of dorsal fin ray elements; and, 4) the number of vertebrae.

Age-validation of a leopard shark (Triakis semifasciata) recaptured after 20 years

On 10 July 1999, vertebrae bearing an oxytetracycline (OTC) time mark were retrieved from a tagged leopard shark (Triakis semifasciata) recaptured in San Francisco Bay, CA, after being at liberty for almost 20 years. An additional long-term leopard shark tag return was received in June 2001, for which growth information (but not vertebrae) was obtained. The first recapture is significant in that it represents the longest at-liberty period for an age-validated (OTC-injected) shark, extends and completes age validation for this species, spanning all age classes up to its estimated average maximum age, and provides an example of the persistence of the OTC time mark in an elasmobranch at liberty for almost 20 years. The recaptured leopard shark made in 2001 also provides valuable information on long-term growth from time of release to time of recapture. Findings are documented here so that other researchers are aware that validation is complete for this species, to present pertinent evidence of considerable interannual variability in growth in this species, and to report observations on processing difficulties relating to the ephemeral nature of the 20-yr-old OTC mark.