Individual performance defines population dynamics. Condition index – a ratio of weight and some function of length – has been louded as an indicator of individual performance and recommended as a ...tool in fisheries management and conservation. However, insufficient understanding of the correlation between individual‐level processes and population‐level responses hinders its adoption. To this end, we use composite modelling to link individual's condition, expressed through the condition index, to population‐level status. We start by modelling ontogeny of European pilchard (Sardina pilchardus, Clupeidae) as a function of food and constant temperature using Dynamic Energy Budget theory. We then provide a framework to simultaneously track the individual‐ and population‐level statistics by incorporating the dynamic energy budget model into an individual‐based model. Lastly, we explore the effects of fishing pressure on the statistics in two constant and food‐limited environmental carrying capacity scenarios. Results show that, regardless of the species' environmental carrying capacity, individual condition index will increase with fishing mortality, that is, with reduction of stock size. Same patterns are observed for gilthead seabream (Sparus aurata, Sparidae), a significantly different species. Condition index can, therefore, in food‐limited populations, be used to (i) estimate population size relative to carrying capacity and (ii) distinguish overfished from underfished populations. Our findings promote a practical way to operationally incorporate the condition index into fisheries management and marine conservation, thus providing additional use for the commonly collected biometric data. Some real‐world applications, however, may require additional research to account for other variables such as fluctuating environmental conditions and individual variability.
•Gilthead sea bream energy content calculated from weight and length.•Structural size is a better predictor of energy content in fish than weight.•Simple but accurate method for calculating energy ...loss and gain from biometric data.•Calculation based on simplified dynamic energy budget (DEB) theory concepts.•Traditional methods underestimate energy gain when fish are fattening up.
Modeling energy content and gain of individuals is of increasing importance in ecosystem modeling, especially in aquaculture and fisheries. Traditional models for estimating the content and gain are either imprecise or expensive, in part because of intensive data requirements. Here we show how routine biometric data (length and wet weight or condition index) can be used to estimate total energy content of fish. Starting with theoretical partitioning between structure and reserves, we create a model to relate energy to the Fulton's condition index. We then use data from cultured sea bream (Sparus aurata L.) to show that the model based on structure should be used to calculate energy content from biometric data. Validation using independent data shows remarkable ability of the model to predict energy content (R2>0.99), while comparison with previously used models demonstrates marked differences in predictions when fish condition is variable. Unlike traditional methods, our model predicts different energy content and gain (or loss) for small fat and large thin fish of equal weight, and can therefore give considerable additional value to biometric data commonly collected in aquaculture, fisheries, and related citizen science programs.
Aquaculture of gilthead seabream, arguably the most important finfish aquaculture species in the Mediterranean, faces changing environmental conditions due to faster-than-average climate change in ...the region. We utilize physiological modelling to estimate effects of moderate and severe climate change on key indices of aquaculture production for all coastal regions of the Mediterranean. Two publicly available global climate change scenarios with daily sea temperature projections serve as forcing for the physiological model during two-year farming cycles representing: (i) reference period starting in 2021, (ii) mid-term effects starting in 2051, and (iii) long-term effects starting in 2091.
We investigate effects of climate change by analyzing changes in time for fish to reach a market size, feed conversion ratio at the market size, and the weight of the fish and the associated feed conversion ratio after two years of farming. Additionally, we track the number of days with sea water temperatures equal to or greater than 28 °C during the two-year period, when gilthead seabream starts experiencing temperature stress. Time to market size generally decreases with climate change from the initial average of 450 days for the reference period by up to 36%. Feed conversion ratio at market size does not appreciably change with climate change, but it does change for the two-year culturing period for up to 10 %, primarily due to faster growth in warmer sea water, and the correspondingly greater weight achieved over the two-year growth cycle.
While the outlook for aquaculture is positive in the mid-term, some indicators show a negative trend in the long-term. The long-term effects of climate change will be greatest in the currently most productive farming regions of the Mediterranean: Levantine, Aegean, and Adriatic seas, and coastal waters of Tunisia. Our analysis focuses on basin-level features, but we provide geospatially referenced simulation results that can be used to analyze effects of climate change in a particular region of interest.
•Mediterranean basin-wide effects of climate change on githead seabream aquaculture.•Key aquaculture performance indicators defined and estimated.•Copernicus data used to drive Dynamic energy budget model on a spatial grid.•Time to market, feed conversion ratio (FCR), and days above 28 °C estimated.
Aquaculture is one of the fastest growing industries in global food production, which raises the need for adopting holistic planning in the allocation of fish farm locations dedicated to aquaculture ...in the context of an ecosystem approach. The future development and expansion of aquaculture will strongly depend on the availability of space to develop the industry in a sustainable manner, or in finding ways to reduce the environmental impact at existing locations. This study assesses the possibility of reducing the impact of aquaculture farming by optimizing on the spatial stocking design of three generations of caged fish. Three spatial stocking scenarios were analyzed using simulated numerical experiments. The analysis was performed using emission estimates and by modelling the dispersion and deposition of organic matter on the seabed with concomitant effects on oxygen concentration. Emissions were estimated according to fish growth predictions, energy requirements, body chemical composition, daily meal requirements (industrial feed), and proximate chemical composition of the feed in a sea bream fish farm. The simulation results show that an optimized spatial stocking design of fish cages can significantly reduce the environmental footprint while simultaneously allowing for an increase in annual fish production and optimal utilization of the farming site. Additionally, our findings suggest that carrying capacity of the farming site based only on the annual maximum biomass of harvested fish does not give optimal production estimates and may contribute to underestimating the productive capacity of cage fish farms.
•Impacts of spatial stocking design of a cage fish farm on the benthic environment.•Numerical modeling simulations performed.•Emission estimates and dispersion and deposition of organic matter on the seabed.•Optimized spatial stocking design can reduce environmental impacts.•Increased production with contributes to sustainable use of fish farms.
The aim of the study was to evaluate the growth, fatty acid profile and concentration of malondialdehyde of muscle tissue of meagre Argyrosomus regius fed diets with different lipid content. The ...long-term experiment was conducted in three feeding groups: A (CP = 52.0; CL = 21.0), B (CP = 56.0; CL = 18.0), C (CP = 48.0; CL = 16.0) with two replicates in marine net cages on Bisage Island, Adriatic Sea over 20 months. At the beginning of the experiment, fish were of equal weight (6.83 ± 1.03 g) and length (8.57 ± 0.49 cm) and were fed to satiation during the experiment. At the end of the experiment, the fish from each feeding group (n = 110) were measured and muscle tissue was collected (n = 60) and stored at −80 °C until analysis. The final weight and condition factor were significantly different (p < 0.05) between the groups. The highest ratio of crude fats and n-3/n-6-fatty acids was found in the muscle tissue of group A. Fish fed diet A also exhibited higher MDA levels compared to fish in the other feeding groups, indicating elevated levels of lipid peroxidation in muscle tissues. Experimental feeding group A showed better growth performance, a higher content of the beneficial fatty acids EPA and DHA and a more favorable n-3/n-6 ratio than feeding groups B and C. Continuously monitoring and adjusting feeding protocols in accordance with lipid content and fatty acid composition could maximize growth and health outcomes in meagre farming.
Integrating mussel and finfish aquaculture has been recognized as a way to increase profits and decrease environmental impacts of finfish aquaculture, but not enough is known about the effects of ...finfish aquaculture on mussel growth. Here we present a pilot study aimed at determining how distance from finfish aquaculture affects mussel growth. To this end, we measured growth and condition index of mussel (Mytilus galloprovincialis) at three different distances (0, 60 and 700 m) from finfish aquaculture in the eastern Adriatic Sea. There was a statistically significant difference in growth of tagged mussels with respect to site. Average measured lengths of mussels at sites 1, 2 and 3 after the 10 months of the experiment were 57.60, 62.73 and 58.66 mm. Mussels grew fastest from March to May, and slowest from July to September, regardless of their position. Condition index showed spatial and temporal variations with higher values during fall and winter (~23), and lower values during spring and summer (~20). Our results show that production cycle in areas traditionally considered suboptimal for aquaculture can be equivalent to the cycle in areas traditionally considered optimal for mussel aquaculture if mussel aquaculture is integrated with finfish aquaculture.
Aquaculture provides more than 50% of all seafood for human consumption. This important industrial sector is already under pressure from climate-change-induced shifts in water column temperature, ...nutrient loads, precipitation patterns, microbial community composition, and ocean acidification, all affecting fish welfare. Disease-related risks are also shifting with important implications for risk from vibriosis, a disease that can lead to massive economic losses. Adaptation to these pressures pose numerous challenges for aquaculture producers, policy makers, and researchers. The dataset AqADAPT aims to help the development of management and adaptation tools by providing (i) measurements of physicochemical (temperature, salinity, total dissolved solids, pH, dissolved oxygen, conductivity, transparency, total nitrogen, ammonia, nitrate, nitrite, total phosphorus, total particulate matter, particulate organic matter, and particulate inorganic matter) and microbiological (heterotrophic (total) bacteria, fecal indicators, and Vibrio abundance) parameters of seawater and (ii) biochemical determination of culturable bacteria in two locations near floating cage fish farms in the Adriatic Sea. Water sampling was conducted seasonally in two fish farms (Cres and Vrgada) and corresponding reference (control) sites between 2019 and 2021 of four vertical layers for a total of 108 observations: the surface, 6 m, 12 m, and the bottom.
We have genotyped 44 fishes caught in the wild (Novigrad Sea, Croatia) using 11 microsatellite tetranucleotide markers. They were divided in two groups and after natural mass spawning, we selected ...500 offspring for genotyping following their labelling with electronic tags. All fish in the parental group could be identified based on unique genotypes, and a significant number of private alleles, the alleles found only in one fish, greatly facilitated subsequent parent-offspring assignments. The majority of potential parents left no progeny, while just six of them generated over 70 %. Such highly skewed reproduction success, observed also in other studies, can quickly lead to a highly inbred population in just a few selection cycles. This kind of genetic analysis is helpful for planning of future selective breeding, where faster progress will be made possible based on the soon to be completed sea bass genome sequence.
Juvenile European sea bass from the same fish stock were selected by successive size grading processes using 2, 3 and 4 mm bar graders at 79, 96 and 99 days post hatching, thus forming three groups ...(n=300) consisting of similar-sized fish that differed by time of each group formation. The growth patterns of fish groups were studied at three temperatures during 5 weeks of rearing. Three-way anova followed by the Tukey multiple comparison test (P<0.05) showed a high dependence of growth on the temperature applied. The smallest size and weight of fish were detected in all groups reared at 19 °C compared with fish held at 21 and 23 °C respectively. Differences in coefficients of variation of lengths were small and insignificant between groups and temperatures. Growth in the length of sea bass juveniles during the test period was a linear function of time and no differences were observed in growth rate among groups at a particular temperature. Growth rates of fish were 0.71 ± 0.02, 0.62 ± 0.01 and 0.52 ± 0.02 mm day⁻¹ at 23, 21 and 19 °C respectively. These results indicated that the variations in body size of juveniles in the test period were not the result of differences in the growth potential of individuals.
