Enrique A Crespo

Centro Nacional Patagonico · Laboratorio de Mamíferos Marinos

Studying trophic habits and their variation over time is crucial for understanding individual and population success. Although many generalist populations appear to use diverse trophic resources, they are often composed of individuals that specialize in only a subset of these resources, a phenomenon known as Individual Trophic Specialization (ITS)....

In recent decades, the growth, physiology and distribution of many elasmobranch species have been altered as a result of environmental changes that affect prey abundance, availability and composition. Consequently, variations in nutrient input during climate events could manifest in the growth of their hard tissues. This study focuses on assessing...

Due to their relationship with prey availability, elasmobranchs with an opportunistic diet can serve as indicators of changes in the marine community, thereby enhancing our understanding of the health of marine ecosystems. In this study, the Zearaja brevicaudata’s trophic ecology was studied, by analysing its stomach contents, aiming to provide evi...

Killer whales ( Orcinus orca ) are highly mobile, large marine apex predators that inhabit all oceans. Despite being the most conspicuous top predator, little is known about their ecology along Patagonia, Argentina. Here, we used carbon (δ ¹³ C) and nitrogen (δ ¹⁵ N) isotope analysis of bone and dentine collagen from killer whales ( n = 13) strande...

To understand the scope and scale of the loss of biodiversity, tools are required that can be applied in a standardized manner to all species globally, spanning realms from land to the open ocean. We used data from the International Union for the Conservation of Nature Red List to provide a synthesis of the conservation status and extinction risk o...

Hybridization is widespread and constitutes an important source of genetic variability and evolution. In animals, its role in generating novel and independent lineages (hybrid speciation) has been strongly debated, with only a few cases supported by genomic data. The South American fur seal (SAfs) Arctocephalus australis is a marine apex predator o...

1. The main issue affecting the conservation of most pinniped species has been identified as interactions with fisheries and aquaculture. In South American waters in particular, this problem has not been well evaluated. Consequently, there is an urgent need for research and conservation measures to address the problem, particularly for species of c...

Península Valdés, Patagonia, Argentina, is recognized as a calving ground for the southern right whale (SRW, Eubalaena australis) population from the southwestern Atlantic Ocean. Previous studies have reported that SRWs feed during their calving season, but little is known about their foraging ecology in this area. Here, we collected photo data of...

A key in species conservation is understanding the amount and distribution of genetic diversity and how environmental changes that occurred in the recent past may have influenced current patterns of population structure. Commerson’s dolphin, Cephalorhynchus commersonii, has two subspecies, one of which is endemic to South America (C. commersonii co...

This is an obituary for William F. Perrin.

This study compares the δ15N values and the trophic position of two seabird species throughout the late Holocene in three regions in the southwestern Atlantic Ocean to assess the hypothesis that the decimation of megafauna led to changes in the trophic position of mesopredators. Modern and ancient mollusk shells were also analyzed to account for ch...

Common dolphins, Delphinus delphis, in the southwestern Atlantic Ocean are subject to incidental mortality in fishing gear. However, no information on trends in abundance or estimates of bycatch mortality are available to evaluate the impact of this threat on the population. This study presents estimates of life history parameters using postmortem...

This chapter reviews the existing data of distribution, population estimates, and trend of the most conspicuous species of pinnipeds and cetaceans in the Argentine sea, in particular the Patagonian ecosystem, exploring foraging ecology and population consumption of prey through time. The chapter focuses on the South American sea lion, South America...

Understanding the recovery of whale populations is critical for developing population-management and conservation strategies. The southern right whale (SRW) Eubalena australis was one of the baleen whale species that has experienced centuries of exploitation. We assess here for the first time the population dynamics of the SRW from the southwestern...

Abundance estimation by means of aerial surveys is prone to errors related to the observer’s performance. We developed a monitoring method based on aerial surveys off the coastline for the Southern Right Whale (Eubalaena australis) in the breeding grounds of the Southwestern Atlantic. These surveys have been taking place since 1999, and whales have...

Conservation actions often rely on some knowledge of the status of a population and can be more effectively implemented if trends in population size are known. Therefore, estimation of abundance is key to contributing to the conservation of the franciscana (Pontoporia blainvillei), the most endangered small cetacean in the western South Atlantic. A...

Durante varias décadas, las interpretaciones sobre las pautas de explotación de pinnípedos en el canal Beagle se basaron sobre los conjuntos zooarqueológicos recuperados en el Segundo Componente de Túnel I. En los últimos años, el análisis sistemático de un número mayor de contextos distribuidos en distintos sectores de la costa norte del canal Bea...

Commerson’s dolphins (Cephalorhynchus commersonii) are separated into the subspecies C. c. commersonii, found along southern South America (SA) and the Falkland Islands/Islas Malvinas (FI/IM), and C. c. kerguelenensis, restricted to the subantarctic Kerguelen Islands (KI). Following the dispersal model proposed for the genus, the latter is thought...

Aquatic ecosystems usually receive pollutants from near industrialized and highly populated zones, through riverine inflow, discharges of sewage or other wastes or the atmosphere. The trophic webs of such ecosystems can be affected by those pollutants, with the inhabitant species manifesting different vulnerabilities for certain compounds. Pollutan...

The estimation and monitoring of population trends are essential to understand the recovery and population dynamics of species that have been affected by humans. When population censuses are carried out for long periods of time, and especially if the species under consideration has wide distributional ranges, different working groups with different...

El Niño-Southern Oscillation (ENSO) and Southern Annular Mode (SAM) indirectly affect tooth growth of marine mammals , through changes in prey abundance, availability, and composition. This is reflected as variation in the dentine deposition, which determines the formation of annual layers, called growth layer groups (GLGs). The aim of this work wa...

The phylogeny and systematics of fur seals and sea lions (Otariidae) have long been studied with diverse data types, including an increasing amount of molecular data. However, only a few phylogenetic relationships have reached acceptance because of strong gene-tree species tree discordance. Divergence times estimates in the group also vary largely...

The South American sea lion, Otaria flavescens, is one of the most conspicuous marine mammals along the coasts of the Atlantic and Pacific Oceans. It has a long history of exploitation throughout its range. In the southwestern Atlantic it was heavily exploited throughout the first half of the twentieth century. As a K-strategist subject to exploita...

Changes in the duration and frequency of foraging trips by female otariids may result in changes in the duration and frequency of lactation bouts and hence influence pup growth rate, unless females modify milk energy density and/or the total amount of milk delivered depending on the trip duration. To test this hypothesis on South American sea lions...

Diphyllobothriosis caused by the Pacific broad tapeworm Adenocephalus pacificus (syn. Diphyllobothrium pacificum) is an emerging parasitic disease reported also from non‐endemic areas, including Europe (Spain). The origin of these human cases is unknown but should be related to fresh marine fish imported from endemic areas. In this study, we molecu...

The poorly known Clymene dolphin (Stenella clymene) is a small oceanic cetacean distributed in tropical and subtropical waters of the Atlantic Ocean. In this study, we report, for the first time, a vagrant individual of Clymene dolphin in Argentina (Rada Tilly) that represents the current southern-most record for this cetacean species. We provide a...

The South American fur seal is distributed on both sides of South America along the Atlantic and Pacific Oceans mostly in sympatry with the South American sea lion. However, there is gap of distribution between 43°S and 29°S in the Pacific coast of approximately 1600 km. The total population was estimated at 320,000 individuals, and the species is...

The South American sea lion is distributed almost continuously from Zorritos, Peru, on the Pacific Ocean to Torres, Brazil, on the Atlantic Ocean. The total population was estimated at 445,000 individuals, and the species is considered as Least Concern in the IUCN Red List. Two evolutionarily significant units were recognized based on molecular dat...

Populations of the South American sea lion (SASL, Otaria byronia) have been intensely exploited for leather and oil in different parts of its distribution range throughout the 19th and 20th centuries, generating large changes in abundance. In Patagonia, the SASL population was reduced by more than 90% of its original abundance, and it began to reco...

Adult specimens of Corynosoma australe Johnston, 1937 were recorded from the intestines of California sea lions, Zalophus californianus (Lesson), from Baja California Peninsula, Mexico, whereas larval forms were collected from two fish species on the Argentinian coast. Adult specimens of C. australe were morphologically characterized by having a cy...

Abstract We present estimates of the seasonal and spatial occupation by pinnipeds of the Wildlife Refuge of Ilha dos Lobos (WRIL), based on aerial photographic censuses. Twenty aerial photographic censuses were analysed between July 2010 and November 2018. To assess monthly differences in the numbers of pinnipeds in the WRIL we used a Generalized L...

Difference among colonies in the population structure of otariids can be driven by philopatry and/or by specializa-tions in the foraging ecology of females. In northern Patago-nia, the South American sea lion (SASL) shows some degree of spatial genetic structure among colonies from north and south zones. This study aims to explore the isotopic nich...

A bstract The phylogeny and systematics of fur seals and sea lions (Otariidae) have long been studied with diverse data types, including an increasing amount of molecular data. However, only a few phylogenetic relationships have reached acceptance pointing at strong gene-tree species tree discordance. Divergence times in the group also vary largely...

Overexploitation of marine communities can lead to modifications in the structure of the food web and can force organisms like elasmobranchs to change their feeding habits. To evaluate the impact that fisheries have on food webs and on the interactions between species, it is necessary to describe and quantify the diet of the species involved and fo...

This study analyzed mtDNA sequences of two bottlenose dolphin subspecies found along the northern Patagonian coast, Argentina: the endangered Tursiops truncatus gephyreus and the data deficient Tursiops trun-catus truncatus. Three haplotypes were recovered from nine samples. The most frequent haplotype represented the coastal morph, also two haplot...

To understand the recovery process and population dynamics of species that were severely depleted, it is essential to monitor their population size and habitat changes throughout their distribution. The South American sea lion (SASL, Otaria flavescens) provides an opportunity to investigate the process of a reduction from sealing and the subsequent...

This study analyzed mtDNA sequences of two bottlenose dolphin subspecies found along the northern Patagonian coast, Argentina: the endangered Tursiops truncatus gephyreus and the data deficient Tursiops truncatus truncatus . Three haplotypes were recovered from nine samples. The most frequent haplotype represented the coastal morph, also two haplot...

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...

Natural or human-induced environmental changes can modify the structure of ecological communities and thus alter food web interactions. After the collapse of hake stocks (Merluccius hubbsi) provoked by fisheries over the Patagonian shelf in 1997 profound changes have taken place in the community, including long-term dietary shifts in some marine ve...

Whale watching in Patagonia began in 1973, with the southern right whale (Eubalaena australis) as a target. Thus far, only short-term effects of whale watching on behaviour have been evaluated. The southern right whale population is increasing locally and expanding to adjacent areas. We evaluated boat effects on the biological system through the an...

Commerson’s dolphin Cephalorhynchus commersonii and Peale’s dolphin Lagenorhynchus australis live in sympatry along the southwestern South Atlantic Ocean, suggesting the existence of some degree of habitat partitioning to reduce their competition for resources. Both species are usually associated with coastal environments, but information on their...

The odontocetes are at the top of the trophic chains, and because they accumulate numerous compounds throughout life, they are considered as bioindicators of ecosystem contamination. This study aimed to analyze the concentrations of trace elements of the short-beak common dolphin (Delphinus delphis) and Fraser's dolphin (Lagenodelphis hosei) from t...

In this article, we present the first results of the determination of season at death performed over eighteen South American sea lions (Otaria flavescens) teeth recovered at Cueva del Negro site (northern coast of the Santa Cruz Province, Patagonia, Argentina). Age and season of death was determined by growth-layer analysis on sea lion teeth. This...

A detailed list of acanthocephalans from Argentina was generated based on 205 published records. The list includes 52 named and 35 undetermined species of Acanthocephala infecting 6 species of invertebrate (2 amphipods, 3 decapods and 1 insect) and 155 species of vertebrate (one cartilaginous fish, 95 bony fishes, 10 amphibians, 3 reptiles, 13 bird...

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...

Social network analysis provides a powerful tool for understanding social organisation of animals. However, in free-ranging populations, it is almost impossible to monitor exhaustively the individuals of a population and to track their associations. Ignoring the issue of imperfect and possibly heterogeneous individual detection can lead to substant...

The knobbed argonaut Argonauta nodosus [Lightfoot], 1786 is a pelagic octopus from tropical and temperate waters with a circum-global distribution in the Southern Hemisphere, between 10°S and 44°S. The species was recorded for the first time in the cold waters of the Patagonian Atlantic coast (45°S) from empty shells. The present record expands the...

Fisheries interactions with non-target marine vertebrates are a worldwide problem. The impact of coastal bottom trawl fisheries on marine mammals has never been evaluated before in the Río de la Plata estuary and adjacent Atlantic Ocean. Our aim was estimate the bycatch per unit effort (BcPUE) and incidental mortality rates of marine mammals caused...

An understanding of the mechanisms that shape animal-population dynamics is a fundamental consideration in conservation biology and ecology. Populations of the species of South-American sea lions (SASLs) Otaria flavescens reveal different growth rates, which variations could be linked to changes in the accessibility of nutritional resources in any...

In this study, 542 individual fish from 20 species from the Patagonian continental shelf of Argentina were examined for acanthocephalans. A total of 1,547 acanthocephalans belonging to 5 species were collected from 18 species of fish. Adult forms were represented by 2 species: Aspersentis johni ( Baylis, 1929 ) (Heteracanthocephalidae) from longtai...

Acanthocephalans display a two-host life cycle that involves arthropods as intermediate hosts and vertebrates as definitive hosts. Some species also use paratenic hosts to bridge the trophic gap between both obligatory hosts. However, the relative role of these paratenic hosts in the transmission to definitive hosts has seldom been assessed quantit...

Since the 1980s, the distribution range of the southern right whale (Eubalaena australis) in Argentina was mostly located in the winter calving grounds around Península Valdés. After the international moratorium that forbade the commercial hunting, southern right whales have shown signs of recovery during the last few decades. Nowadays, it is thoug...

Position of the whales recorded during the zig-zag aerial survey. Latitude, longitude, number of individuals and angle measured with the clinometer. (XLSX)

Change in group composition throughout the season. Type and size (number of individuals) of group recorded during the coastal aerial surveys in Golfo San Matías in the different months. Group: Mother calf pair, Solitary animal, Breeding group; Month: August, September, October. (XLSX)

Change in the distribution of right whales on the coast of Golfo San Matías. Group types and number of whales recorded per segment on the flight in which the highest number of whales was recorded each year. Group: Mother calf pair, Solitary animal, Breeding group; Segment: 1–69; Year: 2007, 2013, 2014, 2015, 2016. (XLSX)

Number of right whales recorded on each coastal aerial survey between Islote Lobos and Caleta de los Loros. Data set used to estimate the population trend in Golfo San Matías, including the year and day (Julian day) in which the flight was made, the number of individuals recorded and the sea state (Beaufort scale). (XLSX)

Group composition in the different hotspots. Group types and total number of whales recorded per segment in each hotspot. The data were extracted from 11 flights performed in Golfo San Matías and 11 flights performed in Península Valdés. Hotspots: Golfo Nuevo, Golfo San José, Golfo San Matías; Group: Mother calf pair, Solitary animal, Breeding grou...

Relative abundance of whales in each hotspot. Total number of whales recorded and kilometres survey in each hotspot in the 11 flights performed in Golfo San Matías that were compared with the 11 flights performed in Península Valdés. Hotspots: Golfo Nuevo, Golfo San José, Golfo San Matías. (XLSX)

Background The Southern Right Whale ( Eubalaena australis ) population of the South–western Atlantic Ocean is recovering. In the breeding ground of Peninsula Valdés, as a consequence of the population growth, expansion to new areas by some types of groups and a change in the habitat use patterns at the coastal area were recorded. Methods We analys...

Stable carbon and nitrogen isotope ratios in the skeletal elements of both ancient and modern marine species from the Beagle Channel were used to compare the structure of Late Holocene and modern food webs, and predict potential changes as a result of a Sea Surface Temperature (SST) increase in the region. Complementary, ancient and modern shells o...

The systematics and phylogeny of Otariidae have been extensively studied for over two centuries. Yet, several relationships, in particular, the monophyly within Arctocephalus, remain unclear. Recent molecular phylogenies only used few concatenated mitochondrial or nuclear genes. Here we reconstructed the Otariidae phylogeny based on whole-genome se...

ABSTRACT. Description and functional interpretation of morphological variation in the dolphin column can be facilitated by recognizing structural units. This information o ers important clues to the proportion of the column involved in the oscillation and displacement of the ukes, and how swimming style can vary among species. Thus, the morphologic...