Mariana Degrati

Mariana Degrati
Centro para el estudio de los Sistemas Marinos (CESIMAR-CENPAT-CONICET) · Marine Mammals Laboratory

PhD

About

33
Publications
10,009
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472
Citations
Additional affiliations
May 2015 - present
Centro para el estudio de los Sistemas Marinos (CESIMAR-CENPAT-CONICET)
Position
  • Researcher
September 2008 - present
National University of Patagonia San Juan Bosco
Position
  • Professor (Assistant)

Publications

Publications (33)
Article
Full-text available
In waters off Península Valdés (PV), Argentina, southern right whales (SRW, Eubalaena australis) are occasionally exposed to domoic acid (DA), a neurotoxin produced by diatoms of the genus Pseudo-nitzschia. Domoic acid toxicity in marine mammals can cause gastrointestinal and neurological clinical signs, alterations in hematologic and endocrine var...
Article
The North Patagonian gulfs, Argentina, support an important population of small pelagic fish (SPF) that play a key role in the marine ecosystem. Here, we assessed the seasonal SPF distribution in Nuevo gulf and San Matías Gulf concerning several environmental variables and the nautical area scattering coefficient (NASC) of Munida gregaria using gen...
Article
Southern right whale-kelp gull biological interaction has been the focus of debates in Península Valdés, Argentina, not only within the academia but also in the public domain. This interaction is perceived as an important and imminent threat to whale conservation and thus to the whale watching activity. When stake-holders complain, sometimes the ma...
Article
Full-text available
Successful conservation strategies require an accurate estimation of population size, and this parameter is one of the most important factors that determine the rate of various evolutionary processes. In this study, we integrated information from genetic, photo-identification, and aerial surveys of dusky dolphins to determine the effective populati...
Article
In spite of the worldwide ecological relevance of Calanus australis and Calanoides carinatus, little is known on the morphology of their mandibular gnathobase edges (MGEs). Thus, in order to further learn about the relationship between MGEs and diet, adults and copepodites of C. australis and C. carinatus collected from northern Patagonian coasts,...
Conference Paper
Full-text available
We report on the investigation of a mass stranding of 68 short-beaked common dolphins (Delphinus delphis) that occurred in Golfo Nuevo, Península Valdés, Argentina in March 2018. Twenty-one of the stranded dolphins were returned alive to the sea, while 47 animals died. Dead dolphins included all ages, with more males than females (29 males and 18 f...
Article
Full-text available
We inspected dusky dolphin (Lagenorhynchus obscurus) group dynamics in Golfo Nuevo and found differences in social organization between cold and warm seasons. Surveys were conducted onboard a research vessel, from which we collected behavioral observations and group fission‐fusion data from 2001 to 2008; we also collected photo‐identification data...
Article
This paper reports on aerial surveys conducted to estimate the relative abundance and trend in growth of the southern right whale (Eubalaena australis) population from Península Valdés. The number of whales counted tripled from 1999 to 2016. We modeled the number of whales, the number of calves, the number of solitary individuals and the number of...
Article
This is the first exploratory study that addresses simultaneously the phytoplankton and mesozooplankton seasonal dynamics associated with some environmental factors in the northern Patagonian gulfs: Golfo Nuevo (GN) and Golfo San José GSJ), Argentina, during an annual cycle (December 2014–2015 and January 2015–2016, respectively). It also reports d...
Article
Full-text available
The gulfs that surround Península Valdés (PV), Golfo Nuevo and Golfo San José in Argentina, are important calving grounds for the southern right whale Eubalaena australis. However, high calf mortality events in recent years could be associated with phycotoxin exposure. The present study evaluated the transfer of domoic acid (DA) from Pseudo-nitzsch...
Article
Full-text available
Península Valdés (PV) is the most austral calving ground for the SW Atlantic population of the Eubalaena australis. Recent studies indicate that E. australis often feeds in PV mainly in late September and October. A microscopic analysis of food chitin remains found in five whale faeces was performed in the present study in an attempt to obtain base...
Article
Full-text available
The dusky dolphin, Lagenorhynchus obscurus, is a coastal small cetacean widespread in the southern hemisphere. Here, we present the first record of cestode parasites present in the blubber of dusky dolphin off Argentine coast. The host examined, corresponded to a 15 years old mature female and measured 171 cm long. Cysts of helminths belonging to C...
Article
Full-text available
The objective of this study was to describe associations between several species of seabirds and dusky dolphins. We investigated during what dolphin activities seabirds were most commonly associated, and the size of flock in relation to the number of dolphins in a group. Since both seabirds and dolphins may display different feeding strategies, we...
Article
Full-text available
Boulevard Almirante Brown 3600, CP (9120) Puerto Madryn, Chubut, Argentina, 3 Instituto Nacional de Investigación y Desarrollo Pesquero, Paseo V. Ocampo Nº 1, Mar del Plata (7600), Argentina The objective of this study was to describe associations between several species of seabirds and dusky dolphins. We investigated during what dolphin activities...
Article
The aim of this work was to analyze the sequential foraging behavior of dusky dolphins (Lagenorhynchus obscurus). Foraging sequences were defined when more than two feeding bouts occur with a traveling bout between them. We hypothesized that traveling costs of searching for prey patches were related to the time spent feeding on a patch. In addition...
Article
Full-text available
During winter, dusky dolphins (Lagenorhynchus obscurus) were observed in coordinated diving apparently in a feeding activity, contrasting with the surface feeding observed during summer. The aim of this work consisted in analyzing the diving activity as an alternative foraging strategy in Argentine dusky dolphins, based on sequential analysis. The...
Article
In Patagonia, Argentina, watching dolphins, especially dusky dolphins (Lagenorhynchus obscurus), is a new tourist activity. Feeding time decreases and time to return to feeding after feeding is abandoned and time it takes a group of dolphins to feed increase in the presence of boats. Such effects on feeding behavior may exert energetic costs on dol...
Article
Full-text available
The management scheme of Marine Protected Areas (MPAs) includes monitoring protocols but such activities are not always carried out. This is the case for Golfo San José, a MPA in northern Patagonia, Argentina. It was created in 1975 for the protection of the southern right whale (Eubalaena australis) breeding grounds. Other components of the system...
Article
Full-text available
We present a new record of sperm whale with notes on diet, age determination and a review of strandings along the continental Argentine coast. A complete necropsy was made in the field, and morphometric data were taken. The specimen stranded was a mature male of 64+ years old. This is the oldest specimen determined for a sperm whale in the Southwes...
Article
Full-text available
Several species of small cetaceans inhabit the coastal area of Patagonia (Argentina), but little is known about their distribution and the degree of overlap between them. The goal of the present study was to build habitat-selection models for small cetaceans in order to assess areas of particular importance for the different species. These models w...
Chapter
It is hypothesized that differences in dusky dolphin foraging behaviors between Argentina and New Zealand are due to differences in how prey are distributed, sizes of prey patches, dolphin abundances in each bay, and presence of plunge-diving gannets in New Zealand versus herding penguins in Argentina. Differences between Argentina and New Zealand...
Article
Full-text available
The use of habitat selection models to predict the likely occurrence of wild populations is an important tool in conservation planning and wildlife management. The goal of our study was to build habitat selection models for the dusky dolphin (Lagenorhynchus obscurus) in Golfo Nuevo, Argentina. Random transects were surveyed by boat in 2002–2007. A...
Article
Full-text available
Dolphin watching is a relatively newly developed tourist activity. Although it is assumed to contribute to the conservation of marine ecosystems, its long-term adverse effects are still unknown. The present work aims to assess the impact of tour vessels on the behavior pattern of dusky dolphins displaying diurnal and cooperative feeding. We evaluat...
Article
Full-text available
Standardized measures of behavior can be powerful tools for predicting effects of human activities on natural populations of mammals. We quantified the diurnal activity budget of dusky dolphins (Lagenorhynchus bscurus) in Golfo Nuevo, Argentina, by examining variation in activity as a function of season and age composition of social groups. Observa...
Data
Full-text available
Standardized measures of behavior can be powerful tools for predicting effects of human activities on natural populations of mammals. We quantified the diurnal activity budget of dusky dolphins (Lagenorhynchus obscurus) in Golfo Nuevo, Argentina, by examining variation in activity as a function of season and age composition of social groups. Observ...
Article
Full-text available
Off Patagonian coasts, Argentina, the dusky dolphin is one of the most common small cetaceans. This species is the aim of newly developed watching activities during summer in Golfo Nuevo. However, the real occurrence and movement pattern are unknown. The objectives of this work were to investigate the predictability of dusky dolphin distribution, g...

Projects

Projects (2)
Project
The southwestern South Atlantic is subject to the pressure of several human activities, acting at different levels and spatial scales, like fisheries, oil transport, and tourism. This marine system is located between the coast and shelf break, with an average depth of 100 mts, extending as far as 400 km from de coastline. The system is supported mainly by middle level species, like anchovy, hake and shrimp. Although the demersal-pelagic system is not of the highest diversity in the world, it supports a high divesity of top predators like seabirds and marine mammals. Trawling is the most common gear, along with jigging. Several trawling fisheries opérate for hake, shrimp and other less important species, including the anchovy, and they produce an important bycatch. Several species of dolphins and sea lions died entangled as bycatch. Also, the main target species for fisheries are the bulk components in the diet of top predators. By the other side, tourism developed all along the coast, based on natural landscapes and wildlife, like dolphins and sea lions. Then sea lions colonies are visited frequently, and dolphins pods are being watching from boats. The evaluation of the effects of both activities sharing the same species, as well as management advice, require different approaches, from population viability analysis, to food webs modelling, from behavior to hábitat use models. The effect of tour boats on dolphin pods was investigated by evaluating changes in behavior and activity budgets, by using Markov chains and transition matrices. Spatial models are though as useful tools in spatial planning and management. Several studies focused on the distribution and habitat use of dusky, common, and Commerson´s dolphins, at different spatial scales. Approaches included GLMs and MAXENT, with presence/absence, encounter rates, or index of use intensity, as response variables depending on available data and spatial resolution and scale. More recently, biotic factors like prey are being surveyed by active acoustics at the same time dolphins movements and abundance, to be incorporated into hábitat use models.
Project
The main goal of project is to understand the principal transfers of toxins at the base of food webs in th shelf zones of El Rincón and northpatagonian gulfs and factors positively influencing in the formation of blooms of toxigenic species. Today, we are investigating the domoic acid transfers and its producing microalgae (Pseudo-nitzschia spp) in coastal pelagic food webs, by using field data and experimental approaches. ----------------------------------------- D’Agostino Valeria C., Mariana Degrati, Viviana Sastre, Norma Santinelli, Bernd Krock, Torben Krohn, Silvana L. Dans, Mónica S. Hoffmeyer. 2017. Domoic acid in a marine pelagic food web: Exposure of southern right whales Eubalaena australis to domoic acid on the Península Valdés calving ground, Argentina. Harmful Algae 68:248–257 D’Agostino, V., M.S. Hoffmeyer, G.O. Almandoz, V. Sastre and M. Degrati. 2015. Potentially toxic Pseudo-nitzschia species in plankton and faecal samples of Eubalaena australis from Península Valdés calving ground, Argentina. Journal of Sea Research, 106:39-43 D’Agostino, V., M.S. Hoffmeyer and M. Degrati. 2015. Faecal analysis of southern right whales (Eubalaena australis) in Península Valdés calving ground, Argentina: Calanus australis, a key prey species. Journal of Marine Biological Association of the United Kingdom. doi:10.1017/S0025315415001897 Fabro, E., G.O. Almandoz, M. E. Ferrario, M.S. Hoffmeyer, R. E. Pettigrosso, R. Uibrig, B.Krock. 2015. Co-occurrence of Dinophysis tripos and pectenotoxins in Argentinean shelf waters. Harmful Algae, 42: 25-33.