Diet composition and feeding habits of the pelagic thresher shark Alopias pelagicus in Eastern Central Pacific Ocean, Ecuadorian waters

2020 ◽  
Vol 100 (5) ◽  
pp. 837-845
Author(s):  
Marcos D. Calle-Morán ◽  
Felipe Galván-Magaña
Keyword(s):  
Diet Composition ◽  
Feeding Habits ◽  
Trophic Niche ◽  
Maturity Stage ◽  
Dosidicus Gigas ◽  
Central Pacific ◽  
Central Pacific Ocean ◽  
Jumbo Squid ◽  
Top Predators ◽  
Thresher Shark

AbstractThe diet and feeding habits of the pelagic thresher shark Alopias pelagicus were analysed based on 104 stomachs (N = 84 females, 20 males) collected off Santa Rosa de Salinas, in the Ecuadorian Pacific. The sharks were caught between February 2008 and January 2009 in artisanal fisheries. The trophic spectrum of A. pelagicus included 19 prey items (10 cephalopods and 9 teleost fishes), the main four prey were the red flying squid Ommastrephes bartramii, jumbo squid Dosidicus gigas, the purpleback flying squid Sthenoteuthis oualaniensis and the South Pacific hake Merluccius gayi. The trophic niche was narrow (Bi = 0.2), thus the pelagic thresher could be considered a specialist predator. The analysis of dietary overlap showed high similarity between the diets of females and males (Cλ = 0.99), immature and mature females (Cλ = 0.81), immature and mature males (Cλ = 0.72), sizes of 141–230 cm TL and 231–321 cm TL (Cλ = 0.97), as well as sharks in rainy season and dry season (Cλ = 0.77). Using canonical of correspondence analysis (CCA), we found similarities in the diet for all categories recorded (sex: canonical r = 0.38, P = 0.97; sexual maturity stage: canonical r = 0.54, P = 0.31; sizes: canonical r = 0.55, P = 0.26; seasons of the year: canonical r = 0.61, P = 0.75). The trophic level estimated for A. pelagicus was 5.0, which is typical of top predators (quaternary consumers or tertiary carnivores).

Feeding habits of the toothed flounder Cyclopsetta querna (Paralichthyidae) of the south-east Gulf of California

2010 ◽  
Vol 91 (6) ◽  
pp. 1225-1230 ◽  
Author(s):  
Felipe Amezcua ◽  
Alfonso Portillo ◽  
Felipe Amezcua-Linares
Keyword(s):  
Gulf Of California ◽  
Diet Composition ◽  
Niche Breadth ◽  
Feeding Habits ◽  
Demersal Fish ◽  
Trophic Niche ◽  
The South ◽  
Top Predators

Feeding habits of the toothed flounder Cyclopsetta querna caught in the south-east Gulf of California were studied. Specimens were collected via demersal fish surveys. Results of this study show that C. querna is a predator that focuses on fish inhabiting the bottom and in particular on tonguefish (Symphurus sp.), midshipman fish (Porichthys sp.) and moray eels (Muraenidae). The diet of the toothed flounder did not vary significantly throughout the period of study, and neither size nor sex-related variations in diet composition were observed. Simpson's index indicates a limited trophic niche breadth with a diet dominated by a limited number of taxa. The estimated TROPH value for C. querna is similar to that estimated for other demersal top predators from the studied area; therefore, the toothed flounder can be considered a top carnivore from the demersal community in the Gulf of California.

Feeding habits and trophic level of the smooth hammerhead shark, Sphyrna zygaena (Carcharhiniformes: Sphyrnidae), off Ecuador

2018 ◽  
Vol 99 (3) ◽  
pp. 673-680 ◽  
Author(s):  
Colombo Estupiñán-Montaño ◽  
Luis Cedeño-Figueroa ◽  
José F. Estupiñán-Ortiz ◽  
Felipe Galván-Magaña ◽  
Alejandro Sandoval-Londoño ◽  
...  
Keyword(s):  
Trophic Level ◽  
Feeding Habits ◽  
Trophic Niche ◽  
Commercial Fishing ◽  
Dosidicus Gigas ◽  
Apex Predators ◽  
Marine Food Webs ◽  
Fishing Vessels ◽  
Marine Food ◽  
Index Of Relative Importance

As apex predators, sharks are known to play an important role in marine food webs. Detailed information on their diet and trophic level is however needed to make clear inferences about their role in the ecosystem. A total of 335 stomachs of smooth hammerhead sharks, Sphyrna zygaena, were obtained from commercial fishing vessels operating in the Ecuadorian Pacific between January and December 2004. A total of 53 prey items were found in the stomachs. According to the Index of Relative Importance (%IRI), cephalopods were the main prey (Dosidicus gigas, Sthenoteuthis oualaniensis, Ancistrocheirus lesueurii and Lolliguncula [Loliolopsis] diomedeae). Sphyrna zygaena was thus confirmed to be a teutophagous species. The estimated trophic level of S. zygaena was between 4.6 and 5.1 (mean ± SD: 4.7 ± 0.16; males: 4.7; females: 4.8). Levin's index (BA) was low (overall: 0.07; males: 0.08; females: 0.09), indicating a narrow trophic niche. We found that sharks <150 cm in total length consumed prey of coastal origin, whereas sharks ≥150 cm foraged in oceanic waters and near the continental shelf. The analyses indicate that S. zygaena is a specialized predator consuming mainly squids.

Reconstructing ecosystem dynamics in the central Pacific Ocean, 1952–1998. I. Estimating population biomass and recruitment of tunas and billfishes

2002 ◽  
Vol 59 (11) ◽  
pp. 1724-1735 ◽  
Author(s):  
Sean P Cox ◽  
Steven J.D. Martell ◽  
Carl J Walters ◽  
Timothy E Essington ◽  
James F Kitchell ◽  
...  
Keyword(s):  
Stock Assessment ◽  
Ecosystem Dynamics ◽  
Central Pacific ◽  
Central Pacific Ocean ◽  
Makaira Nigricans ◽  
Top Predators ◽  
Production Models ◽  
Thunnus Obesus ◽  
Age Structured ◽  
Commercial Yield

Commercial yield of tunas in the central Pacific increased severalfold between 1952 and 1998. We developed age-structured production models that incorporate information from multiple fisheries to estimate population biomass and recruitment trends of tunas (Thunnus alalunga, Thunnus albacares, Thunnus obesus, and Katsuwonus pelamis) and billfish in the central north Pacific (0°N to 40°N and 130°E to 150°W). Our results suggest that all tuna stocks remain above 40% of 1950s levels, whereas blue marlin (Makaira nigricans) declined to 21% and swordfish (Xiphias gladius) to 56%. Estimated biomasses of juvenile bigeye (T. obsesus) and yellowfin (T. albacares) tuna increased to 112 and 129%, respectively, of 1950s levels. Juvenile albacore (T. alalunga) decreased during the 1970s and 1980s but recovered to historical highs (121%) in recent years. Skipjack (K. pelamis) remained relatively stable between 1952 and 1980, declined by 35% between 1981 and 1990, and then increased to 68% of 1950s levels. These changes generally represent decreases in top predators and increases in small tunas, which make up their prey. Application of stock assessment methods set in a food web context provides an important step toward developing a method that recognizes fishery exploitation as a component of ecosystem dynamics.

scholarly journals Same Diet, Different Strategies: Variability of Individual Feeding Habits across Three Populations of Ambrosi’s Cave Salamander (Hydromantes ambrosii)

Diversity ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 180
Author(s):  
Enrico Lunghi ◽  
Fabio Cianferoni ◽  
Filippo Ceccolini ◽  
Yahui Zhao ◽  
Raoul Manenti ◽  
...  
Keyword(s):  
Diet Composition ◽  
Feeding Habits ◽  
Population Level ◽  
Trophic Niche ◽  
Trophic Dynamics ◽  
Extrinsic Factors ◽  
Surrounding Environment ◽  
New Information ◽  
Depth Study ◽  
Different Populations

European cave salamanders of the genus Hydromantes are a group of eight species endemic to Italy and south-eastern France. Knowledge on the trophic niche of European Hydromantes is poor, and the few available studies only partially investigate their feeding habits. We performed an in-depth study on the trophic niche of the Ambrosi’s cave salamander (H. ambrosii), assessing the potential divergences among three different populations. All the populations had a similar diet composition, showing a wider trophic niche in fall compared to spring. In only one population, “true specialists” were present; however, in all three populations, generalist individuals always represented the larger proportion. Interspecific and intraspecific competition did not play an important role in determining individual dietary specialisation in H. ambrosii; contrarily, the characteristics of the surrounding environment seemed to be an important factor. The best body conditions were observed in the population located in the site where the non-arboreal vegetation cover was the highest. Besides providing new information on the trophic niche of H. ambrosii, we here showed that studies encompassing both intrinsic and extrinsic factors at the population level are needed to fully understand the trophic dynamics occurring among European cave salamanders.

scholarly journals A Bayesian Multilevel Ordinal Regression Model for Fish Maturity Data: Difference in Maturity Ogives of Skipjack Tuna (Katsuwonus pelamis) Between Schools in the Western and Central Pacific Ocean

2021 ◽  
Vol 8 ◽  
Author(s):  
Jie Cao ◽  
Xuefang Wang ◽  
Matthew D. Damiano ◽  
Cheng Zhou ◽  
Jiangfeng Zhu
Keyword(s):  
Pacific Ocean ◽  
Ordinal Data ◽  
Gonadosomatic Index ◽  
Fork Length ◽  
Ordinal Regression ◽  
Maturity Stage ◽  
Skipjack Tuna ◽  
Central Pacific ◽  
Free Swimming ◽  
Central Pacific Ocean

The maturity ogive is vital to defining the fraction of a population capable of reproduction. In this study, we proposed a novel approach, a Bayesian multilevel ordinal regression (i.e., Bayesian continuation ratio model), to model the maturity ogive. The model assumes that the observed maturity stage originates from the categorization of latent continuous variables. We demonstrated this approach by testing whether there are differences in the maturity ogive of skipjack tuna (Katsuonus pelamis) in the western and central Pacific Ocean between two school types, i.e., free-swimming and floating-object-associated schools. The model results show that K. pelamis, given the same fork length, are more likely to have a higher maturity stage in a free-swimming school than those associated with floating objects. The gonadosomatic index revealed the same conclusion. Our results indicate that fish aggregation devices (FADs) could negatively affect the maturity of K. pelamis and consequently reduce the population reproductive potential. This study provides (1) an alternative approach to analyze fisheries ordinal data; (2) important quantitative evidence to evaluate the existing ecological hypotheses; and (3) implications for tuna fisheries management.

scholarly journals The biology and ecology of the jumbo squid Dosidicus gigas (Cephalopoda) in Chilean waters: a review

2016 ◽  
Vol 43 (3) ◽  
pp. 402-414
Author(s):  
Christian M. Ibáñez ◽  
Roger D. Sepúlveda ◽  
Patricio Ulloa ◽  
Friedemann Keyl ◽  
M. Cecilia Pardo-Gandarillas
Keyword(s):  
Life History ◽  
Pacific Ocean ◽  
Size Structure ◽  
Feeding Habits ◽  
Marine Ecosystem ◽  
Background Information ◽  
Dosidicus Gigas ◽  
Southeastern Pacific ◽  
Jumbo Squid ◽  
History Of

The jumbo squid Dosidicus gigas is the most abundant cephalopod species in the southeastern Pacific Ocean, which supports the biggest cephalopod fishery in the world. Due to its growing economic importance, the population growth and distributional expansion of this squid is being increasingly studied. Nevertheless, some basic features of the biology of D. gigas are still unknown or have been poorly investigated. In this review we summarize the known information regarding the biology and ecology of this species in the southeastern Pacific Ocean; we focus on the Chilean region in order to propose hypotheses and research lines for a better understanding the life history of this organism. Available data on the size structure, reproduction and genetics of D. gigas allows us to propose hypotheses related to the squid’s life history traits. Based on the current literature and publications of colleagues, we propose two hypotheses regarding the effect of spatial variation on the life history of D. gigas. Hypothesis 1: Squids mature at large sizes and spawn in oceanic waters with warm temperatures where paralarvae and juveniles develop. Immature squids migrate near shore to feed, grow and mature, and then return to the offshore sites to spawn. Hypothesis 2: Alternatively, juvenile D. gigas in the oceanic zone do not migrate to coastal waters and mature at small sizes compared to individuals living near the coast that mature at larger size and migrate to oceanic waters to spawn. We provide background information about the feeding behavior and parasitism of this species, suggesting that D. gigas is an important trophic link in the southeastern Pacific marine ecosystem. However, more studies on the feeding habits, reproduction and parasite load are needed not only to test hypotheses proposed in this study, but also to advance the overall knowledge of this species.

Food and feeding habits of jumbo squid Dosidicus gigas (Cephalopoda: Ommastrephidae) from the Gulf of California, Mexico

2003 ◽  
Vol 83 (3) ◽  
pp. 507-522 ◽  
Author(s):  
Unai Markaida ◽  
Oscar Sosa-Nishizaki
Keyword(s):  
Gulf Of California ◽  
Environmental Changes ◽  
Feeding Habits ◽  
Stomach Contents ◽  
Dosidicus Gigas ◽  
Fish Prey ◽  
Monthly Basis ◽  
Jumbo Squid ◽  
Food And Feeding ◽  
Northern Anchovy

Stomach contents of 533 jumbo squid, Dosidicus gigas, ranging between 14·5 and 87·5 cm dorsal mantle length were collected on a monthly basis in the central Gulf of California from November 1995 to April 1997. Fish prey were identified by sagittal otoliths, cephalopods by beaks and crustaceans by exoskeletal features. The diet was dominated by Benthosema panamense, an abundant near-shore nyctoepipelagic myctophid that forms dense aggregations. Another myctophid, Triphoturus mexicanus, several micronektonic squid, pelagic red crab and small pelagic fish such as northern anchovy and Pacific sardine played a secondary role. The largest differences in diet were due to spatial and monthly changes, while differences regarding squid size or sex were smaller. Prey size (averaging 5–7 cm) and prey number did not vary with size of jumbo squid. Jumbo squid in the slopes of the Guaymas basin feed on abundant schooling mesopelagic micronekton of annual nature with a quick response to environmental changes, which could partly explain the large annual fluctuations of this commercial resource.

Energy accumulated in the somatic tissues of the jumbo squid, Dosidicus gigas, off Peru

2018 ◽  
Vol 25 (2) ◽  
pp. 444
Author(s):  
Yanran WEI ◽  
Xinjun Chen ◽  
Dongming LIN ◽  
Zimo CHEN
Keyword(s):  
Dosidicus Gigas ◽  
Jumbo Squid ◽  
Somatic Tissues
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