Biology subjects

Bartolino, V.

Publications and source records attributed to Bartolino, V..

3 recordsLinked to original sources

bioRxiv2025

Reduced size of larvae and small fish linked to warming and reduced prey density

Body size is a integrative trait that has declined across ecological assemblages in the last decades. Changes in body size of early life stages and small-bodied fish are driven by complex interactions between size-dependent mortality, and temperature- and food dependent growth, and can have consequences for recruitment to the adult stock and food availability to predators. While the mechanisms can be difficult to disentangle using observational data alone, simple indicators such as mean size can provide important information about ecosystem conditions as oceans rapidly change. Using 30 years of observations from the IBTS-MIK ichthyoplankton survey in Skagerrak and Kattegat in combination with sea surface temperature data, we investigated changes in the body size of early life stages and small-bodied fishes for 10 commercial and non-commercial species using geostatistical mixed models, and trends in prey density using generalized additive models. We found positive associations between chlorophyll-a concentration and length in 8 species (3 significant), and negative associations between temperature and length in 9 species (4 significant). Standardized indices of length revealed negative trends over time for all species since 2010, and all species were smaller in 2024 compared to 2000. The decline in size since 2010 varied between 30%-1%, with a mean of 14% and 9% for species predominantly found in Skagerrak and Kattegat, respectively. The trend of decreased body sizes since 2010 coincides with rapid declines in Calanus spp. -- a key prey predicted to decline in this area at the edge of their distribution area due to climate change. In Skagerrak it also coincides with a decline in the density of large copepods (> 0.25 mm). The synchronous declines in larval size across taxonomically diverse species experiencing different rates of exploitation suggest a common response to changing environmental conditions, which could have cascading effects throughout marine food webs.

ecology↗

bioRxiv2025

Weak effects of local prey density and spatial overlap on predation intensity in a temperate marine ecosystem

Quantifying the impact of lower trophic level species abundance on higher trophic level predators (and vice versa) is critical for understanding marine ecosystem dynamics and for implementing ecosystem-based management. Trophic ecosystem models generally predict a tight coupling between prey and fish predators, such that higher abundance of lower trophic species increases abundance of higher trophic level predators. This assumes that predator feeding rates are limited by prey availability to some degree. Despite being a key component of predator-prey interactions and multi-species fisheries management, relatively few studies have assessed the impacts of prey availability on predation patterns of mobile, generalist fish predators using spatiotemporal models and local-scale stomach content, predator, and prey data. In this study, we explore the association between local density of key prey and predator stomach contents, and predator-prey spatiotemporal overlap and predation indices, using the Baltic Sea as a case study. We use three decades of spatially resolved biomass and stomach content data on Atlantic cod (Gadus morhua), and biomass data on three of its key prey: herring (Clupea harengus), the isopod Saduria entomon, and sprat (Sprattus sprattus). Using geostatistical generalized linear mixed effects models fitted to relative biomass density and prey-weight-per-predator-weight, we estimate spatiotemporal trends and annual indices of biomass weighted and area-expanded per-capita and population-level predation, predator-prey overlap, and the correlation between these indices. Range shifts have resulted in reduced predator-prey overlap over time, which is now the lowest in three decades. For Saduria, we find an association between prey availability and stomach contents, but not for herring or sprat. Similarly, only in Saduria do we find a positive correlation between population-level predation indices and the spatiotemporal overlap. Although behavioral interactions with pelagic prey are challenging to infer from stomach content and acoustic data due to high mobility leading to fine-scale spatiotemporal mismatch, the weak connection with local-scale availability, and low correlation between population-level predation and spatial overlap, could imply weaker coupling between pelagic prey and cod than previously thought. These findings provide key information on the strength of species interactions, which is crucial for the continued development of multispecies models and ecosystem-based fisheries management.

ecology↗

bioRxiv2024

Quantifying competition between two demersal fish species from spatiotemporal stomach content data

Inference on competition is often made on indirect patterns of potential competition, such as population trends and spatiotemporal overlap in diet and distribution. However, these indicators do not test if the contested resources are limited in supply, nor if they decline as competitor biomass increases. Using stomach content and biomass data, we evaluate food competition between Atlantic cod (Gadus morhua) and flounder (Platichthys spp.) in the Baltic Sea. We quantify diet overlap and fit geostatistical mixed models to evaluate effects of local-scale covariates on stomach contents. The dietary overlap is low and does not decline with predator density. We find that cod feed less on the isopod Saduria entomon at high flounder densities. However, the total prey weight in cod is not affected by flounder densities. This suggests interspecific food competition is not limiting the overall feeding of cod, but affects its diet composition. In addition, we find support for intraspecific food competition in large cod and flounder. Our study illustrates the importance of local-scale processes when inferring competition from stomach content data.

ecology↗