Dr. Urzúa-Osorio, Ángel

Marine trophodynamics refer to the transfer of energy from prey to predators. In marine invertebrates and fishes, the nutrients obtained through the consumption of food and/or prey are stored as energy reserves in certain tissues and/or organs including the liver, muscle, or gonads, and that these are subsequently used as bioenergetic fuel for highly energy-demanding fundamental physiological processes. In the southern Humboldt Current System, the interaction between two highly migratory resources and top species has been observed: the swordfish (Xiphias gladius) and its prey the jumbo squid (Dosidicus gigas). Because of this trophic interaction, these species store large amounts of energy (as lipids and fatty acids) in their main organs. However, how the fatty acid profile varies in the various organs of the predator and its prey is still unknown, as is its potential use as trophic biomarkers and the ecophysiological role it plays. Our results showed a moderate similarity between the fatty acid profile of the digestive gland of D. gigas with the profiles of the liver, gonad, and muscle of X. gladius, particularly with fatty acids: palmitic (C16:0), stearic (C18:0), oleic (C18:1n9), gadoleic (C20:1), EPA (C20:5n3), and DHA (C22:6n3). Our findings on the use of fatty acids as biomarkers of the interaction between two highly migratory species in the southern Humboldt System may reveal the degree of preference swordfish have for preying on jumbo squid, particularly through the consumption of the digestive gland. In both species, a high bioenergetic fuel content characterized by a predominance of saturated, monounsaturated, and polyunsaturated fatty acids may be necessary to sustain the high energy costs involved in their migratory and reproductive processes in the Humboldt Current system.

The traceability of fish species and their resulting food products is essential to maintain the global supply of these goods, allowing us to distinguish and reconstruct the origin and history of their production chain. One way to trace food is through biochemical determinations, which aid in identifying their geographical origin quickly. This study analyzed the fatty acid (FA) profiles of highly migratory fishery resource species (HMRS) from the Southeastern Pacific Ocean (SEPO), and their use as potential tools to determine the geographic origin and nutritional condition of these marine resources. The fatty acids (FAs) presented in fillet or muscle tissue of 18 HMRS were measured as FA methyl esters by gas chromatography. Our results reveal that the swordfish Xiphias gladius presented the greatest variety of FAs, strongly characterized by the presence of saturated, monounsaturated, and polyunsaturated FAs. A similar trend of high diversity in all classes of FAs was observed in tuna species (i.e., Thunnus alalunga; T. albacares; T. obesus), oilfish (Ruvettus pretiosus) and escolar fish (Lepidocybium flavobrunneum). In turn, Lampris guttatus, Makaira indica, and Tetrapturus audax presented an intermediate variety of FAs and the highest amount of saturated and monounsaturated FAs of the evaluated species. Finally, Luvarus imperialis, Coryphaena hippurus and the sharks (Lamna nasus; Alopias vulpinus; Prionace glauca; Isurus oxyrinchus; Sphyrna zygaena) presented a low diversity of FAs, with only saturated FAs strongly predominating. Regarding the total concentration of FAs, the highest average values were recorded in X. gladius, L. flavobrunneum and R. pretiosus. The present study revealed notable differences in the FA compositions of the muscle of diverse HMRS from the SEPO off the coast of Chile, with the swordfish showing the healthiest FAs (i.e., mono and polyunsaturated) for human consumption. The data on FAs collected for HMRS could be used as a reference to characterize the FA profiles of other fisheries in the SEPO (e.g., coastal pelagic fishes). In an ecosystem approach, our findings help us to understand how essential nutrients (i.e., FA biomolecules) are transferred through the marine food web in the SEPO, revealing the diet type and/or feeding habits of HMRS considered as top predators. Furthermore, identifying the FA profiles of fishery resources at a spatial level provides crucial information for their management and conservation, particularly in those resources that are overexploited and also have a critical nutritional importance for human consumption.

Parasites can alter the reproductive performance of their hosts, and to avoid or mitigate the resulting fitness loss, hosts may increase their current reproductive output to compensate for the future loss due to the parasitic infection. Fecundity compensation can be exploited by parasites for their own transmission (exploitation of host compensatory responses by parasites). However, this phenomenon has rarely been reported in second intermediate hosts of trematodes and its mechanisms and consequences largely unexplored. Along the east coast of the South Pacific, the second intermediate host, the mollusk Fissurella crassa, has been observed to display higher muscular foot, greater shell length and weight, and a higher gonadosomatic index when parasitized by metacercariaes of Proctoeces humboldti compared to non-parasitized hosts. In this study, we examined the histology, biochemistry (glucose, lipids, and proteins), and levels of sex hormones (estradiol and progesterone) in both parasitized and non-parasitized female individuals of F. crassa. Our findings revealed that the gonad of parasitized limpets had a higher density of oocytes, but these had a smaller individual area. Additionally, the gonadal tissue of parasitized limpets exhibited lower glucose content but higher lipid content. Notably, the levels of progesterone increased with parasite intensity. These results suggest that F. crassa possesses the ability to compensate for the negative effects of parasites by increasing the number of oocytes through biochemical and hormonal mechanisms. Our study contributes to the limited research on the impact of metacercariae on the reproduction of second intermediate hosts. Furthermore, we discuss how these changes in parasitized limpets could benefit parasite transmission.

The integrated biochemical condition (IBC) of gonads is closely related to the reproductive success of highly migratory marine species. The IBC of gonads can be influenced not only by size and/or age, but also by environmental conditions. Here, female swordfish, Xiphias gladius, that migrate to temperate regions with a marked seasonality (e.g., the Southeastern Pacific Ocean, SEPO) were compared in relation to the IBCs (lipids, proteins, glucose and, fatty acid profiles) of their gonads; individuals with two body size ranges and distinct degrees of sexual maturity were evaluated, and considered as: small and/or virginal (SV: <170 cm lower jaw fork-length (LJFL), oocyte size (OS) <0.08 mm) vs large and/or maturing females (LM: >190 cm LJFL, OS >0.133 mm). This comparison was conducted in two environmentally contrasting seasons (winter vs spring). Our results showed that the gonadosomatic index (GSI) was significantly higher in LM than SV. Lipid contents varied significantly between seasons and body sizes. The highest lipid concentrations were recorded in the spring in large females. No significant differences were found when comparing the protein and glucose contents of the two evaluated seasons or body size ranges of the studied females. In turn, the fatty acid (FA) profiles of female gonads significantly varied for both seasons and body size ranges. A high content of saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs) and poly-unsaturated fatty acids (PUFAs) were recorded in female gonads in the spring. The SFAs C16:0 and C18:0, the MUFA C18:1n9, and the essential PUFA C22:6n3 were the main contributors to the observed differences between spring and winter. These results could be used as indicators of the nutritional condition and health status of swordfish individuals. Hence, the IBC of female swordfish gonads have great potential to aid in estimating survival rates and stock abundances of this species. The integration of this information constitutes an asset in fishery management models with an ecosystem approach.

This study focused on gathering available information on Pleuroncodes monodon, a widely distributed crustacean in the Humboldt Current System. Off the Chilean coast, this species presents benthic habits and constitutes the main resource of the industrial crustacean fishery; many studies have been carried out on its life cycle during the last century. In contrast, off the coast of Peru, this species exhibits mainly pelagic habits, with latent information gaps on aspects of its life history and no commercial fishery activities, such as catching, taking or harvesting from the marine environment. P. monodon is an ecologically important species, as a source of energy for its predators, which include invertebrates, birds, marine mammals and fish of commercial interest. Thus, P. monodon seems to play a key role in this ecosystem, mainly as an intermediate link between top predators and the first links in the food chain. In addition, this species presents various adaptation strategies to the changing oceanographic parameters of the areas it inhabits, even tolerating hypoxic environments and great depths in order to avoid being predated. Likewise, from an economic viewpoint, it has a high commercial value as a marine bioresource with great potential in the pharmaceutical and food industries. Considering this, more studies must be carried out to corroborate the biological, ecological, and fishing importance of this species in order to generate efficient management measures and ensure a sustainable fishery.

In the wide distribution range of the red squat lobster Pleuroncodes monodon in the Southeast Pacific Ocean, there is an important nursery area on the southern coast of Chile. The new juvenile individuals from this nursery area are directly recruited into the adult squat lobster population, which is exploited by industrial fisheries. Despite the importance of new P. monodon juveniles for recruitment estimations in fishery management models, their bioenergetic condition and/or nutritional status at the onset of their benthic phase remain unknown, as are the differences in the biochemical composition and energy reserves of the two sexes, which could help explain the cost of the first breeding event in females. Therefore, in new juvenile squat lobsters with the same degree of immaturity, we quantified and compared between the sexes (female vs. male): the size (cephalothorax length, CL), body biomass (dry weight and organic matter), biochemical composition (proteins, glucose, and lipids), and fatty acid profiles (FAs). The results indicate that the CL of new juveniles was similar between the sexes, while the dry weight and organic matter presented significant differences, with higher values in new juvenile females (NJF) than new juvenile males (NJM). Similarly, the NJF had a higher content of proteins, glucose, and lipids than NJM. The FAs also showed significant differences between the sexes; the NJF had a higher content than NJM in all fatty acid classes (i.e., saturated, monounsaturated, and polyunsaturated), with the FAs DHA (C22:6n‐3), EPA (C20:5n‐3), oleic (C18:1n‐9), palmitic (C16:0), and eicosatrienoic (C20:3n‐3) significantly contributing to the differentiation of FA profiles between the sexes. All of the aforementioned differences among the multiple variables of the bioenergetic condition can indicate biochemical adaptations in the storage capacity of energy reserves, particularly among NJF that must support the high energy cost of the first reproductive event (characterized by embryo production and incubation), which occurs during the austral winter, a period predominated by cold‐water temperatures and scarce food availability in the habitat. Overall, our findings have significant implications in fishery management models. In this case, defining the bioenergetic condition of the new juvenile squat lobsters can aid in predicting the density and stability of the adult population, which is exploited by commercial fisheries.

The red squat lobster Pleuroncodes monodon is an important fishery resource in the Humboldt Current System (HCS). This decapod is exploited in two fishing units: (a) the northern fishing unit (NFU, from 26°S to 30°S) and (b) the southern fishing unit (SFU, from 32°S to 37°S), each of which have an adjacent nursery area that is the source of recruits to replace the exploited adult populations (in the NFU: off the coast of Coquimbo (28°S) and in the SFU: off the coast of Concepción (36°S)). Marked spatial differences in the environmental conditions of the NFU and SFU, and the biogeographic break that exists between these nursery areas (30°S) may promote changes in the bioenergetic condition of new P. monodon juveniles. To evaluate this, we analyzed the bioenergetic condition (measured as: body mass, lipids, proteins, glucose, and energy) of new juvenile females in the main nursery areas off the Chilean coast. The juvenile females from the SFU showed a higher body mass than those from the NFU. Consistently, the juvenile females from the SFU had a higher content of lipids, proteins, and glucose than those from the NFU, indicative of higher energy contents and a higher lipid/protein ratio in the south compared to the north. Considering the current overexploitation of this fishery resource in the HCS, it is essential to understand how the bioenergetic condition of juvenile females of P. monodon may vary in nursery areas at different latitudes in order to generate sustainable fishery management policies with an ecological approach, designed specifically to each fishing unit. Furthermore, identifying the latitudinal variations of these biochemical compounds in P. monodon juveniles can elucidate the geographic origin of red squat lobsters that present a ”better bioenergetic condition” in the HCS, which may significantly benefit sustainable fishing certification processes.

Fishery pressure on nursery areas of smooth hammerhead in northern Peruvian coast have become a serious threat to sustainability of this resource. Even though, some management actions focused on conservation of the smooth hammerhead populations were proposed in recent years, their scientific foundations are often limited, and biomass of smooth hammerhead in Peruvian waters continues to decrease. To inform management and conservation, this study aims to evaluate the trophic niche of smooth hammerhead juveniles from three nursery areas in the northern Peruvian coast using stable isotope and fatty acid analyses. First, we compared the environmental characteristics of each nursery area (i.e., sea surface temperature and chlorophyll-a concentration) and concluded that nursery areas differed significantly and consistently in sea surface temperature. Subsequently, we evaluated isotopic composition of carbon and nitrogen and fatty acid profiles of muscle and liver tissues collected from juvenile smooth hammerhead from each nursery area. We found that juvenile smooth hammerhead captured in San José were enriched in heavier 13C and 15N isotopes compared to those captured in Máncora and Salaverry. Furthermore, the broadest isotopic niches were observed in juveniles from Máncora, whereas isotopic niches of juveniles from Salaverry and San José were narrower. This difference is primarily driven by the Humboldt Current System and associated upwelling of cold and nutrient rich water that drives increased primary production in San José and, to a less extent, in Salaverry. Compared to smooth hammerhead juveniles from Máncora, those from San José and Salaverry were characterised by higher essential fatty acid concentrations related to pelagic and migratory prey. We conclude that smooth hammerhead juveniles from three nursery areas in the northern Peruvian coast differ significantly in their trophic niches. Thus, management and conservation efforts should consider each nursery area as a unique juvenile stock associated with a unique ecosystem and recognize the dependence of smooth hammerhead recruitment in San José and Salaverry on the productivity driven by the Humboldt Current System.

The red squat lobster Pleuroncodes monodon is a species of high commercial value that inhabits the Humboldt Current System. Along the Chilean coast, two populations are exploited by the fishing industry, one located off the coast of Coquimbo and the other off the coast of Concepción. Yet, it is unknown whether there are differences in the “bioenergetic fuel” (measured as lipid content and fatty acid profile) of juvenile populations of these two fishing units and whether these bioenergetic compounds can be modulated by differences in the environmental parameters (such as temperature or chlorophyll-a) of their breeding areas. To shed some light on this, we measured the lipid content and fatty acid profiles of the viscera and muscle of juvenile female red squat lobsters from these two fishing units, specifically from breeding areas near long-exploited fishing grounds: a) the northern fishing unit (NFU, from 26°S to 30°S) and b) the southern fishing unit (SFU, from 32°S to 37°S). We found differences in the lipid content, fatty acid profiles, and ratios of saturated fatty acids (C16:0/C18:0) of juvenile females from these two locations. In addition, the essential fatty acids (DHA/EPA) found in the viscera versus the muscle of these lobsters varied significantly. Juvenile females from the SFU (i.e. Concepción) showed a higher lipid content compared to the juvenile females from the NFU (i.e. Coquimbo). Consistently, individuals from the SFU had a higher content of fatty acids, which also proved to be richer in saturated and monounsaturated fatty acids compared to those from the NFU. Our results are important for the fisheries in both areas because these juvenile populations are the source of new recruits for the adult populations that are exploited by the fishing industry. Our study also aids in determining which populations are healthier or of better quality in bioenergetic terms. Furthermore, increasing the incorporation of bioenergetic parameters in fishery models is essential for the recruitment and stock assessment within an ecosystem approach, since it allows for the evaluation of the nutritional condition of different fishing populations.

The Western Antarctic Peninsula (WAP) is a hotspot for environmental change and has a strong environmental gradient from North to South. Here, for the first time we used adult individuals of the bivalve Aequiyoldia eightsii to evaluate large-scale spatial variation in the biochemical composition (measured as lipid, protein and fatty acids) and energy content, as a proxy for nutritional condition, of three populations along the WAP: O’Higgins Research Station in the north (63.3_x0001_S), Yelcho Research Station in mid-WAP (64.9_x0001_S) and Rothera Research Station further south(67.6_x0001_S). The results reveal significantly higher quantities of lipids (L), proteins (P),energy (E) and total fatty acids (FA) in the northern population (O’Higgins)(L: 8.33 ± 1.32%; P: 22.34 ± 3.16%; E: 171.53 ± 17.70 Joules; FA: 16.33 ± 0.98 mg g)than in the mid-WAP population (Yelcho) (L: 6.23 ± 0.84%; P: 18.63 ± 1.17%;E: 136.67 ± 7.08 Joules; FA: 10.93 ± 0.63 mg g) and southern population (Rothera)(L: 4.60 ± 0.51%; P: 13.11 ± 0.98%; E: 98.37 ± 5.67 Joules; FA: 7.58 ± 0.48 mg g). We hypothesize these differences in the nutritional condition could be related to a number of biological and environmental characteristics. Our results can be interpreted as a consequence of differences in phenology at each location; differences in somatic and gametogenic growth rhythms. Contrasting environmental conditions throughout the WAP such as seawater temperature, quantity and quality of food from both planktonic and sediment sources, likely have an effect on the metabolism and nutritional intake of this species.