Ricardo Tafur

Distribución, captura y CPUE del calamar gigante Dosidicus gigas a bordo de buques calamareros (27 de julio al 26 de agosto de 1997)

Evaluación poblacional del recurso concha de abanico (Argopecten purpuratus) en Bahía Independencia. 18 de abril - 02 de mayo de 1996

Reproductive biology of jumbo squid Dosidicus gigas in relation to environmental variability of the northern Humboldt Current System

Mar Ecol Progr Ser, 2010

Dosidicus gigas is a monocyclic ommastrephid squid and is an important component of its ecosystem... more Dosidicus gigas is a monocyclic ommastrephid squid and is an important component of its ecosystems in the Eastern Pacific Ocean. The species shows variable reproductive characteristics; among these are 3 spatially separated groups of size-at-maturity. Biological data from the industrial fisheries of the Peruvian Humboldt Current System (HCS) from 1991 to 2007 were analyzed. Changes in reproduction patterns allow jumbo squid to cope with productivity changes in their environment. In the HCS, low productivity is related to warm water masses prevailing during warm periods, and high productivity is found for cool water masses during cool periods. Three general features related to reproduction enabling the squid to adjust to changes have been identified: (1) variable size-at-maturity, (2) temporal decoupling of male and female formation of reproductive tissue in order to temporally distribute the required energy and (3) changing sex-ratios. Smaller sizes-at-maturity are found in warm water masses, specimens maturing at larger sizes in cool water masses. Females mature at the end of their life which leads to a j-shaped increase in maturity when plotted against mantle length, while males mature at a medium size which results in an s-shaped form of maturation. The 3 groups of size-at-maturity proposed in earlier studies may not actually exist, and may only be an observational artifact from a continuous change in size-at-maturity between 2 extremes. KEY WORDS: Dosidicus gigas · Cephalopoda · Reproductive patterns · Interannual variability · Size-at-maturity · Energy availability · Peru Resale or republication not permitted without written consent of the publisher Editorial responsibility: Hans Heinrich Janssen,

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Evaluación poblacional de la concha de abanico (Argopecten purpuratus) en Bahía de Sechura e Isla Lobos de Tierra. Julio 1999

Aspectos reproductivos del pulpo (Octopus mimus) en el área de Callao

Determinación de las condiciones bioambientales de la poza La Arenilla, La Punta, Callao

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El calamar gigante Dosidicus gigas, primavera 2001. Crucero BIC Shinko Maru Nº 3

Crucero de investigación del calamar gigante BIC SNP-2 9903-04, 23 marzo al 12 abril 1999

Investigación de crustáceos de profundidad en la zona de Pisco - Callao

Población de la concha de abanico (Argopecten purpuratus) en el área de Chimbote, del 16 al 24 de setiembre 1999

Embryos and Rhynchoteuthion Paralarvae of the Jumbo Flying Squid Dosidicus gigas (Cephalopoda) Obtained through Artificial Fertilization from Peruvian Waters

Fisheries Science Fs, Dec 1, 1999

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Community Structure Changes of Subtidal Macrobenthos of Hard Substrate from Palomino Isle, Callao - Perú, from 1997 to 2001

Investigaciones marinas, 2002

Optimality-based model of phytoplankton growth and diazotrophy

Marine Ecology Progress Series, 2013

Significant gaps exist in our understanding of early sea turtle life stages. Dispersal and habita... more Significant gaps exist in our understanding of early sea turtle life stages. Dispersal and habitat use of young oceanic sea turtles are largely inferred. Historically, available tracking technology and tag attachment methods were limited by small body sizes and rapid growth of neonate sea turtles. We tested methods in the laboratory for attaching small solar-powered satellite tags to neonate loggerhead sea turtles Caretta caretta, including harnesses, hard epoxy and neoprene-silicone mounts. Non-harness attachments were tested on turtles with clean carapaces and carapaces treated with an acrylic base-coat. Turtle growth and condition were measured among treatment and control groups. We tested surrogate solar cells, coated with clear silicone antifoulant for biofouling and performance, and field tested the performance of 7 solar-powered satellite tags on neonate loggerheads released off southeastern Florida (USA). Attachments with acrylic base-coats remained affixed 4-to 8-fold longer than on untreated carapaces. Harness attachments resulted in long-term tag retention (> 60 d). However, harness and hard epoxy attachments did not adjust for turtle growth; we do not recommend these methods for rapidly growing neonate turtles. The method with longest retention was a neoprene-silicone attachment on an acrylic base-coat. Growth and condition were comparable among treated and control turtles using this flexible neoprene-silicone-acrylic attachment. Field-tested tags transmitted for 38 to 172 d. There were significant differences in charge rates of tags treated with an antifoulant and untreated tags; however, all tags charged optimally and transmitted high-quality locations. Our data suggest that small solar-powered tags are viable tools for monitoring the in-water behavior of oceanic sea turtles.

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Interannual variability in size structure, age, and growth of jumbo squid (Dosidicus gigas) assessed by modal progression analysis

ICES Journal of Marine Science, 2011

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Embryos and rhynchoteuthion paralarvae of the jumbo flying squid, Dosidicus gigas,(Cephalopoda) obtained through artificial fertilization from Peruvian waters

FISHERIES SCIENCE-TOKYO-, 1999

Abstract; Shipboard artificial fertilization experiments were carried out during November 1997 us... more

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Comprehensive Model of Jumbo Squid Dosidicus gigas Trophic Ecology in the Northern Humboldt Current System

by Monique Simier, Ricardo Tafur, ricardo tafur - jimenez, and Ana Alegre Norza Sior

PLoS ONE, 2014

The jumbo squid Dosidicus gigas plays an important role in marine food webs both as predator and ... more The jumbo squid Dosidicus gigas plays an important role in marine food webs both as predator and prey. We investigated the ontogenetic and spatiotemporal variability of the diet composition of jumbo squid in the northern Humboldt Current system. For that purpose we applied several statistical methods to an extensive dataset of 3,618 jumbo squid non empty stomachs collected off Peru from 2004 to 2011. A total of 55 prey taxa was identified that we aggregated into eleven groups. Our results evidenced a large variability in prey composition as already observed in other systems. However, our data do not support the hypothesis that jumbo squids select the most abundant or energetic taxon in a prey assemblage, neglecting the other available prey. Indeed, multinomial model predictions showed that stomach fullness increased with the number of prey taxa, while most stomachs with low contents contained one or two prey taxa only. Our results therefore question the common hypothesis that predators seek locally dense aggregations of monospecific prey. In addition D. gigas consumes very few anchovy Engraulis ringens in Peru, whereas a tremendous biomass of anchovy is potentially available. It seems that D. gigas cannot reach the oxygen unsaturated waters very close to the coast, where the bulk of anchovy occurs. Indeed, even if jumbo squid can forage in hypoxic deep waters during the day, surface normoxic waters are then required to recover its maintenance respiration (or energy?). Oxygen concentration could thus limit the co-occurrence of both species and then preclude predator-prey interactions. Finally we propose a conceptual model illustrating the opportunistic foraging behaviour of jumbo squid impacted by ontogenetic migration and potentially constrained by oxygen saturation in surface waters.

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Tracking habitat and resource use for the jumbo squid Dosidicus gigas: a stable isotope analysis in the Northern Humboldt Current System

by Pepe Espinoza, Michelle Graco, and Ricardo Tafur

Marine Biology, 2012

To determine the habitat and resource use of Dosidicus gigas in the Northern Humboldt Current Sys... more To determine the habitat and resource use of Dosidicus gigas in the Northern Humboldt Current System, we analysed carbon and nitrogen stable isotopes of 234 individuals collected during 2008-2010. Large variations in mantle stable isotope ratios were recorded, with values ranging from -19.1 to -15.1 % (d 13 C) and from 7.4 to 20.5 % (d 15 N). Most of the variation was explained by latitude, followed by distance to shelf break for carbon and by squid size for nitrogen. Latitudinal variations with increasing values from north to south were also found in zooplankton samples and were related to changes in isotope baseline values probably due to oxygen minimum zones that occur off Peru. This similar latitudinal trend in both zooplankton and D. gigas samples reveals that D. gigas is a relatively resident species at the scale of its isotopic turnover rate (i.e. a few weeks), even if this is not necessarily the case at the scale of its life. A small but significant size effect on d 13 C values suggests that jumbo squid perform offshore-onshore ontogenic migration, with juveniles distributed offshore. For nitrogen, the high interindividual variability observed with mantle length indicates that D. gigas can prey on a high variety of resources at any stage of their life cycle. This large-scale study off the coast of Peru provides further evidence that D. gigas have the capability to explore a wide range of habitats and resources at any stage of their life. Communicated by C. Harrod.

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Tracking habitat and resource use for Dosidicus gigas: a stable isotope analysis in the Northern Humboldt Current System

by Pepe Espinoza and Ricardo Tafur

Marine Biology, Sep 12, 2013

To determine the habitat and resource use of Dosidicus gigas in the Northern Humboldt Current Sys... more To determine the habitat and resource use of Dosidicus gigas in the Northern Humboldt Current System, we analysed carbon and nitrogen stable isotopes of 234 individuals collected during 2008-2010. Large variations in mantle stable isotope ratios were recorded, with values ranging from -19.1 to -15.1 % (d 13 C) and from 7.4 to 20.5 % (d 15 N). Most of the variation was explained by latitude, followed by distance to shelf break for carbon and by squid size for nitrogen. Latitudinal variations with increasing values from north to south were also found in zooplankton samples and were related to changes in isotope baseline values probably due to oxygen minimum zones that occur off Peru. This similar latitudinal trend in both zooplankton and D. gigas samples reveals that D. gigas is a relatively resident species at the scale of its isotopic turnover rate (i.e. a few weeks), even if this is not necessarily the case at the scale of its life. A small but significant size effect on d 13 C values suggests that jumbo squid perform offshore-onshore ontogenic migration, with juveniles distributed offshore. For nitrogen, the high interindividual variability observed with mantle length indicates that D. gigas can prey on a high variety of resources at any stage of their life cycle. This large-scale study off the coast of Peru provides further evidence that D. gigas have the capability to explore a wide range of habitats and resources at any stage of their life. Communicated by C. Harrod.

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Comprehensive Model of Jumbo Squid Dosidicus gigas Trophic Ecology in the Northern Humboldt Current System

by Pepe Espinoza, Ana Alegre Norza Sior, and Ricardo Tafur

Plos One, Jan 20, 2014

The jumbo squid Dosidicus gigas plays an important role in marine food webs both as predator and ... more The jumbo squid Dosidicus gigas plays an important role in marine food webs both as predator and prey. We investigated the ontogenetic and spatiotemporal variability of the diet composition of jumbo squid in the northern Humboldt Current system. For that purpose we applied several statistical methods to an extensive dataset of 3,618 jumbo squid non empty stomachs collected off Peru from 2004 to 2011. A total of 55 prey taxa was identified that we aggregated into eleven groups. Our results evidenced a large variability in prey composition as already observed in other systems. However, our data do not support the hypothesis that jumbo squids select the most abundant or energetic taxon in a prey assemblage, neglecting the other available prey. Indeed, multinomial model predictions showed that stomach fullness increased with the number of prey taxa, while most stomachs with low contents contained one or two prey taxa only. Our results therefore question the common hypothesis that predators seek locally dense aggregations of monospecific prey. In addition D. gigas consumes very few anchovy Engraulis ringens in Peru, whereas a tremendous biomass of anchovy is potentially available. It seems that D. gigas cannot reach the oxygen unsaturated waters very close to the coast, where the bulk of anchovy occurs. Indeed, even if jumbo squid can forage in hypoxic deep waters during the day, surface normoxic waters are then required to recover its maintenance respiration (or energy?). Oxygen concentration could thus limit the co-occurrence of both species and then preclude predator-prey interactions. Finally we propose a conceptual model illustrating the opportunistic foraging behaviour of jumbo squid impacted by ontogenetic migration and potentially constrained by oxygen saturation in surface waters.

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Comprehensive Model of Jumbo Squid Dosidicus gigas Trophic Ecology in the Northern Humboldt Current System

by Monique Simier and Ricardo Tafur

PLoS ONE, 2014

The jumbo squid Dosidicus gigas plays an important role in marine food webs both as predator and ... more The jumbo squid Dosidicus gigas plays an important role in marine food webs both as predator and prey. We investigated the ontogenetic and spatiotemporal variability of the diet composition of jumbo squid in the northern Humboldt Current system. For that purpose we applied several statistical methods to an extensive dataset of 3,618 jumbo squid non empty stomachs collected off Peru from 2004 to 2011. A total of 55 prey taxa was identified that we aggregated into eleven groups. Our results evidenced a large variability in prey composition as already observed in other systems. However, our data do not support the hypothesis that jumbo squids select the most abundant or energetic taxon in a prey assemblage, neglecting the other available prey. Indeed, multinomial model predictions showed that stomach fullness increased with the number of prey taxa, while most stomachs with low contents contained one or two prey taxa only. Our results therefore question the common hypothesis that predators seek locally dense aggregations of monospecific prey. In addition D. gigas consumes very few anchovy Engraulis ringens in Peru, whereas a tremendous biomass of anchovy is potentially available. It seems that D. gigas cannot reach the oxygen unsaturated waters very close to the coast, where the bulk of anchovy occurs. Indeed, even if jumbo squid can forage in hypoxic deep waters during the day, surface normoxic waters are then required to recover its maintenance respiration (or energy?). Oxygen concentration could thus limit the co-occurrence of both species and then preclude predator-prey interactions. Finally we propose a conceptual model illustrating the opportunistic foraging behaviour of jumbo squid impacted by ontogenetic migration and potentially constrained by oxygen saturation in surface waters.

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