Modern fish are able to produce a plethora of different traces (both bioturbation and bioerosion structures) according to several behaviours, yet only five ichnotaxa have been interpreted as produced by the activity of fish in the fossil record. Many taphonomic factors may favour the non-fossilization of many of these traces and, even fossilized, they could have been misinterpreted. In this contribution, shallow and bilobed traces produced by the feeding activity of the perciform fish Diplodus vulgaris (Sparidae) in the estuary of the Piedras River (Lepe, Huelva, SW Spain) are described. Neoichnological study and comparison of these bioturbation structures with the fossil record allow associating them as Cruziana- and Rusophycus-like traces, i.e. traces with features very similar to those of such ichnogenera. Since these ichnotaxa have been commonly interpreted as the result of the locomotion and resting of different kinds of invertebrates, in order to get a better understanding of the marine and continental fossil record, we also propose taking into account fish as potential producers of this kind of traces in future paleoichnological studies

Gas-hydrate occurrences along the Chilean margin have been widely documented, but the processes associated with fluid escapes caused by the dissociation of gas hydrates are still unknown. We report a seabed morphology growth related to fluid migration offshore Lebu associated with mud cones by analysing oxygen and deuterium stable water isotopes in pore water, bathymetric, biological and sedimentological data. A relief was observed at − 127 m water depth with five peaks. Enrichment values of δ¹⁸O (0.0–1.8‰) and δD (0.0–5.6‰) evidenced past hydrate melting. The orientation of the relief could be associated with faults and fractures, which constitute pathways for fluid migration. The benthic foraminifera observed can be associated with cold seep areas. We model that the mud cones correspond to mud growing processes related to past gas-hydrate dissociation. The integration of (i) the seismic data analysis performed in the surrounding area, (ii) the orientation of our studied relief, (iii) the infaunal foraminifera observed, (iv) the grain size and (v) the total organic matter and isotope values revealed that this area was formerly characterised by the presence of gas hydrates. Hence, this part of the Chilean margin represents a suitable area for investigating fluid-migration processes.

Our study investigates the trophic ecology of the anchoveta (Engraulis ringens). The anchoveta plays a key role in the Greater Humboldt Ecosystem and is extensively exploited by countries from the south-eastern Pacific Ocean. For a comprehensive study of trophic ecology, we employed a combined approach that included stomach content analysis, stable isotope analysis, and scaled mass index of body condition. Our results showed that the multivariate composition of the diet varies significantly between life stage and fishing zones in Chile. Copepods and euphausiids emerged as the dominant prey found in the stomachs across all fisheries zones. Stable isotope analysis revealed significant differences among different zones. The scaled mass index values were higher in the northern zone compared to the southern zones, for both juveniles and adults. This research carries significant implications for fisheries management and conservation efforts, such as the development of targeted management strategies that address variations in the trophic structure of anchoveta across different life stages and fishing zones.

Toxoplasma gondii, a parasitic protozoan, may infect most warm-blooded animals, including humans and carnivores. Our study focused on alien-invasive American minks (Neogale vison) and domestic cats (Felis catus) in the Valdivian Temperate Rainforest, Chile. The main goal was to investigate the relationship between their dietary habits and T. gondii exposure in the Valdivia River watershed. To detect T. gondii exposure, blood serum samples from 49 domestic cats and 40 American minks were analyzed using an ELISA, and stable isotope analysis of δ15N and δ13C from vibrissae was performed to determine the dietary habits of both species. Relationships between T. gondii exposure and dietary habits were explored using generalized linear mixed-effects models. American minks that were T. gondii seropositive exhibited a broader prey range compared to seropositive domestic cats, with minimal dietary overlap between the two groups. Exposure of domestic cats to T. gondii had no significant association with any isotope value or prey item in their diet. In American minks, we found a positive and significant association between the proportion of Domestic chicken (Gallus gallus domesticus) in the diet and high δ15N values with T. gondii exposure. This suggests that domestic species prey related to anthropogenic areas, and the consumption of high-trophic-level prey, may contribute to T. gondii exposure in American minks. Conversely, contrary to previous hypotheses, consumption of rodents showed no significant association with T. gondii exposure in either species. Our findings emphasize the importance of further research to investigate trophic interactions in the transmission dynamics of T. gondii in the Valdivian Temperate Rainforest.

Fish growth analysis is a fundamental part of research in fisheries biology, aquaculture, and physiology. However, there is the question of whether the addition of mass and length depends on the amount of energy a prey can deliver. This study tested the hypothesis that there is an effect on the length/weight ratio of the predator, under the premise that fish that ingest prey with a greater amount of energy will have greater mass growth, in contrast to those that ingest food with lesser energy. The fish in this experiment was under controlled laboratory conditions under two types of food treatment and one control (low energy vs high energy amount). The energy-rich treatment had a significant effect on the mass increase (GLM; F = 2.72; P = 0.031), and the length/weight ratio was greater in the fish under the energy-rich treatment (ANCOVA; F = 3.59; P = 0.043). However, the IGR showed that fish presented low rates of intrinsic size growth (ANOVA; F = 0.189; P = 0.828).