Reproduction, diet and habitat use of leopard sharks, Triakis semifasciata (Girard), in Humboldt Bay, California, USA

2005 ◽  
Vol 56 (8) ◽  
pp. 1089 ◽  
Author(s):  
David A. Ebert ◽  
Thomas B. Ebert
Keyword(s):  
Habitat Use ◽  
Sexual Segregation ◽  
Minor Importance ◽  
Nursery Ground ◽  
Relative Importance ◽  
Fish Eggs ◽  
Index Of Relative Importance ◽  
Diet Analyses ◽  
Triakis Semifasciata ◽  
Leopard Sharks

A total of 312 female leopard sharks (Triakis semifasciata) was sampled in Humboldt Bay, California, USA, an important nursery ground for this species, during the spring month of May from 1983 to 1984 and 1985. Sexual segregation is strong as only three males were observed in the study area. Females ranged in size from 120 to 154 cm total length, and all examined were determined to be mature. Overall, 130 out of 153 females examined in early May contained term embryos. The number of embryos per female ranged from 1 to 37 with larger females tending to possess more embryos. Of the 159 individuals examined in late May, no females were found carrying embryos and most were ovulating. Diet analyses revealed that, overall, fish eggs (Atherinopsis californiensis) at 48.0%, had the highest percentage Index of Relative Importance (%IRI), followed by the cancrid crabs, Cancer antennarius (29.8%) and C. magister (11.6%). All other prey were of relatively minor importance, cumulatively representing 10.6% of the overall diet. Adults shift their diet after parturition: early May sharks fed almost exclusively on fish eggs, while crabs were more important in those examined in late May.

scholarly journals Food and Trophic Relationships of Four Mullet Fish (Mugilidae) in the Shatt Al-Arab River, Iraq

2019 ◽  
Vol 7 (1) ◽  
Author(s):  
Abdul-Razak M Mohamed ◽  
Abdullah N. Abood
Keyword(s):  
Food Item ◽  
Feeding Activity ◽  
Food Composition ◽  
Trophic Relationships ◽  
Relative Importance ◽  
Fish Eggs ◽  
Direct Competition ◽  
Competition For Food ◽  
Index Of Relative Importance ◽  
Monthly Variations

Food composition and feeding relationships of four mullet species, Planliza abu, P. subviridis, P. klunzingeri and Osteomugil speigleri from the Shatt Al-Arab River, Iraq, were assessed during 2016-2017.Fish were captured by gill nets, cast net and electro-fishing. The index of relative importance (IRI%) of food item was determined by combined the frequency of occurrence and points methods. Monthly variations in feeding activity and intensity of all species were observed. All species were herbivorous and P. abu and  P. klunzingeri were considered non-specialized feeders, while P. subviridis and O. speigleri were low specialist feeders. P. abu fed mainly on diatoms (38.6%), high plants (21.7%), algae (15.9%), detritus (15.3%), fish eggs (6.9%) and zooplankton (1.6%).The diet of P. subviridis constituted from diatoms (42.2%), high plants (20.9%), detritus (17.7%), algae (15.9%), zooplankton (2.0%) and fish eggs (1.8%). P. klunzingeri fed mainly on diatoms (35.5%), high plants (29.3%), detritus (16.4%), algae (13.4%), fish eggs (4.1%) and zooplankton (2.4%). O. speigleri were consumed mainly diatoms (52.0%), detritus (17.8%), algae (16.6%), high plants (10.7%), zooplankton (2.5%) and fish eggs (2.4%).Similarity dendrogram among fish species based on their diet showed high significant overlaps among the mullet species. It means that these species might be in direct competition for food in the Shatt Al-Arab River.

scholarly journals Changing patterns of habitat use by southern right whales (Eubalaena australis) on their nursery ground at Península Valdés, Argentina, and in their long-range movements

2020 ◽  
pp. 133-143
Author(s):  
Victoria J. Rowntree ◽  
Roger S. Payne ◽  
Donald M. Schell
Keyword(s):  
Habitat Use ◽  
Nitrogen Isotope ◽  
Isotope Ratios ◽  
Small Scale ◽  
Nursery Ground ◽  
Adult Males ◽  
Human Disturbances ◽  
Eubalaena Australis ◽  
Right Whales ◽  
Southern Right Whales

Southern right whales (Eubalaena australis) have been studied on their nursery ground at Península Valdés, Argentina, every year since 1970. Since 1990, 1,208 individuals have been identified from photographs taken during annual aerial surveys; 618 whales were seen in two or more years. Patterns of habitat use have changed during the study in ways which suggest that right whales may be capable of substantial behavioral and ecological flexibility. One male and three females from Península Valdés have been sighted on other nursery grounds (Tristan da Cunha and southern Brazil). Three individuals from Península Valdés were sighted on feeding grounds off Shag Rocks and South Georgia. Some right whales from Península Valdés showed carbon and nitrogen isotope ratios very similar to those seen in right whales off South Africa, while others showed distinctive isotope ratios indicating that they fed in a different area. Whales of all ages and both sexes moved frequently between three major regions of concentration on the Península Valdés nursery ground. Subadults and adult females with calves were resighted at higher rates than adult males and females in non-calf years. Changes in the geographic distribution of whales at the Península include: (1) abandonment of a major region of concentration; (2) establishment of a nursery area adjacent to thecentre of a growing whalewatching industry; and (3) small-scale shifts in distribution, possibly in response to natural and human disturbances.

Tissue-specific isotope trophic discrimination factors and turnover rates in a marine elasmobranch: empirical and modeling results

2012 ◽  
Vol 69 (3) ◽  
pp. 551-564 ◽  
Author(s):  
Luis Malpica-Cruz ◽  
Sharon Z. Herzka ◽  
Oscar Sosa-Nishizaki ◽  
Juan Pablo Lazo
Keyword(s):  
Natural Populations ◽  
Nitrogen Isotope ◽  
Cartilage Tissue ◽  
Turnover Rates ◽  
Isotopic Equilibrium ◽  
Isotope Turnover ◽  
Discrimination Factors ◽  
Triakis Semifasciata ◽  
Leopard Sharks ◽  
Trophic Discrimination

There are very few studies reporting isotopic trophic discrimination factors and turnover rates for marine elasmobranchs. A controlled laboratory experiment was conducted to estimate carbon and nitrogen isotope trophic discrimination factors and isotope turnover rates for blood, liver, muscle, cartilage tissue, and fin samples of neonate to young-of-the-year leopard sharks ( Triakis semifasciata ). Trophic discrimination factors varied (0.13‰–1.98‰ for δ13C and 1.08‰–1.76‰ for δ15N). Tissues reached or were close to isotopic equilibrium to the new diet after about a threefold biomass gain and 192 days. Liver and blood exhibited faster isotope turnover than muscle, cartilage tissue, and fin samples, and carbon isotopes turned over faster than those of nitrogen. Metabolic turnover contributed substantially to isotopic turnover, which differs from most reports for young marine teleosts. We modeled the relationship between muscle turnover rates and shark size by coupling laboratory results with growth rate estimates for natural populations. Model predictions for small, medium, and large wild leopard sharks indicate the time to isotopic equilibrium is from one to several years.

scholarly journals Low latitude habitat use patterns of a recovering population of humpback whales

2018 ◽  
Vol 98 (5) ◽  
pp. 1087-1096 ◽  
Author(s):  
Maria Isabel Carvalho Gonçalves ◽  
Renata Santoro De Sousa-Lima ◽  
Niel Nascimento Teixeira ◽  
Maria Emilia Morete ◽  
Gustavo Henrique De Carvalho ◽  
...  
Keyword(s):  
Habitat Use ◽  
Cost Effective ◽  
Humpback Whales ◽  
Anthropogenic Activity ◽  
Small Scale ◽  
Nursery Ground ◽  
Social Strategies ◽  
Low Latitude ◽  
Use Patterns ◽  
Key Factor

The coast of Brazil is an important low latitude nursery ground for humpback whales (Megaptera novaeangliae). The number of humpback whales in this region has increased and its population is reoccupying areas where it has been depleted during the whaling period. The goal of this study was to conduct land-based observations during 2014 and 2015 to characterize patterns of habitat use and relative abundance of humpback whales that migrate to one of these reoccupation areas: Serra Grande, Bahia state. The observed mean group size was 2.12 ± 0.96 individuals and did not vary through the reproductive season nor between years. Dyads (32.9%) and singletons (26.7%) were more frequently observed, and groups with calves represented 21.2% of the sightings. The mean number of whales counted per hour increased from 2014 (3.44 ± 3.35) to 2015 (5.12 ± 4.18). Habitat use varied during the season; whales used shallower waters closer to shore as the season progressed. The spatial distribution of groups with calves was dependent on the presence and number of escorts. Spatial segregation of groups with calves closer to shore is a key factor in understanding the overall distribution of whales in the area, suggesting that social strategies are affected by environmental factors, as seen in other wintering grounds. Small-scale studies from land-based stations, in areas such as this where there is no previous knowledge about the species, are cost effective. They provide information about the overall behavioural and spatial patterns while anthropogenic activity is still low, allowing habitat protection and management decisions before implementation and increase of human activities.

Forage, Habitat use, and Sexual Segregation by a Tropical Deer (Cervus Eldi Thamin) in a Dipterocarp Forest

2001 ◽  
Vol 82 (3) ◽  
pp. 848-857 ◽  
Author(s):  
W. J. McShea ◽  
M. Aung ◽  
D. Poszig ◽  
C. Wemmer ◽  
S. Monfort
Keyword(s):  
Habitat Use ◽  
Sexual Segregation ◽  
Dipterocarp Forest

scholarly journals Spatial and seasonal changes in the diet of Oligosarcus hepsetus (Characiformes, Characidae) in a Brazilian Reservoir

2005 ◽  
Vol 65 (1) ◽  
pp. 1-8 ◽  
Author(s):  
F. G Araújo ◽  
C. C Andrade ◽  
R. N Santos ◽  
A. F. G. N Santos ◽  
L. N Santos
Keyword(s):  
Seasonal Changes ◽  
Prey Capture ◽  
Gut Contents ◽  
Relative Importance ◽  
Food Items ◽  
Dietary Shifts ◽  
Index Of Relative Importance ◽  
Almost All ◽  
Previous Autumn ◽  
Very High

We assessed spatial and seasonal changes in the diet of Oligosarcus hepsetus in order to describe the strategy developed by this species that allows their very high abundance in Lajes reservoir, Rio de Janeiro, Brazil. Fish samplings were carried out using gill nets, deployed during ca. 12 and 24 hours, between April 2001 and May 2002. A total of 289 individuals were examined, of which 97 showed gut contents. We used the index of relative importance (IRI) to compare probable dietary shifts, and the frequency of occurrence (% OC) to analyze possible ontogenetic influences on feeding. O. hepsetus showed carnivorous habits, feeding preferably on fish and insects, the latter of which occurred in 71.0% of the guts presenting contents. O. hepsetus consumed different items along the three reservoir zones: insects (61.0% IRI) and Cichla monoculus (38.9% IRI) in the lower zone; Lepidoptera (57.0% IRI) in the middle zone; and C. monoculus (77.0% IRI) in the upper zone. Food items changed seasonally with C. monoculus predominating in autumn 2001, and Hymenoptera and Lepidoptera in the winter. In spring almost all food was Lepidoptera (99.8% IRI), while in the summer Hemiptera dominated in the diet. In autumn 2002 Hemiptera (97.0% IRI) was dominant, in significant contrast with the previous autumn. Individuals smaller than 190 mm SL fed heavily on insects, while fishes predominated in the diet of individuals larger than 190 mm SL. Shifts in prey-capture ability among length classes suggest decreasing intraspecific competition. A higher food plasticity seems to be the strategy employed by this opportunist species, which used food resources available in the reservoir.

scholarly journals Bio-Ecological Traits of Western Tubenose Goby Proterorhinus semilunaris (Heckel, 1837): A Key to Understand Its Invasion Success

Water ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 1247 ◽  
Author(s):  
Gülşah Saç
Keyword(s):  
Standard Length ◽  
Natural Habitat ◽  
Invasion Success ◽  
Biological Traits ◽  
Relative Importance ◽  
Ecological Traits ◽  
Tubenose Goby ◽  
Significant Difference ◽  
Index Of Relative Importance ◽  
Proterorhinus Semilunaris

This study aims to contribute to the limited knowledge on the bio-ecological traits of the native Western tubenose goby, Proterorhinus semilunaris, which is considered to invade many inland waters in Europe and North America. During monthly sampling surveys from March 2012 to June 2013, the species was collected from the four stations in the Istranca River (Turkey) by electrofishing. The standard length and body weight of 310 samples varied between 1.4–6.1 cm and 0.08–7.09 g, respectively. The sex ratio of female to male was found to be 1.7:1.0, with a significant difference. The values of the exponent b in the length–weight relationship were approximately 3 for females, males, and all individuals, indicating an isometric growth. The size at first sexual maturity was 2.44 cm standard length (SL) for females and 2.29 cm SL for males. Absolute fecundity ranged from 56 to 344 eggs with a mean of 164 eggs. The food composition of the species comprised of 8 major groups: Insecta (Diptera, Ephemeroptera, Plecoptera, Odonata, Trichoptera, Coleoptera), Arachnida, Annelida, Gastropoda, Crustacea, Pisces, plant, and detritus. According to the results of modified index of relative importance (MI) and index of relative importance (IRI), insect and Diptera were the most prevalent prey for this fish. The present study has provided baseline information on the basic biological traits of the fish in its natural habitat for further understanding of this species success of invasion.

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