Nikos Papandroulakis

Hellenic Centre for Marine Research | hcmr · Institute of Marine Biology, Biotechnology and Aquaculture

Fin abnormalities are common in reared fish. They mainly consist of partial to complete lack of rays and severe abnormalities of fin-supporting skeletal elements, which develop during the larval stage, up to the completion of fin skeleton ontogeny. This study reports a new abnormal condition, ray-resorption syndrome (RSS), which developed after the...

Aquaculture is expected to account for two-thirds of global fish consumption by 2030, highlighting the need for sustainable and efficient practices. Feeding is crucial to aquaculture success, influenced by factors like fish size, environment, and health. This study addresses a gap in feeding control for sea cages by developing a real-time monitorin...

The terms “offshore” and “open ocean” have been used to describe aquaculture sites that are further from the coast or in higher energy environments. Neither term has been clearly defined in the scientific literature nor in a legal context, and the terms are often used interchangeably. These and other related terms (for example “exposed”, “high-ener...

Aquaculture is anticipated to contribute to two-thirds of the world’s fish consumption by 2030, emphasizing the need for innovative methods to optimize practices for economic viability, social responsibility, and environmental sustainability. Feeding practices play a pivotal role in aquaculture success and the feeding requirements are dynamic, infl...

Digital Twin technology has emerged to become a key enabling technology in the ongoing transition into Industry 4.0. A Digital Twin is in essence a digital representation of an asset that provides better insight into its dynamics by combining a priori knowledge of the system through mathematical models with online data acquired from sensors and ins...

Introduction Farmed fish like European seabass (Dicentrarchus labrax) anticipate meals if these are provided at one or multiple fixed times during the day. The increase in locomotor activity is typically known as food anticipatory activity (FAA) and can be observed several hours prior to feeding. Measuring FAA is often done by demand feeders or ext...

Pinpointing thermal tolerance thresholds for commercially important species, such as aquaculture finfish, under acute and chronic thermal stress is becoming increasingly relevant in the context of climate change. While experimental research, traditionally quantified by the determination of the Critical Thermal Maximum ( C T m a x ), offers valuable...

Marine aquaculture has been expanding rapidly in recent years, driven by the growing demand for marine products. However, this expansion has led to increased competition for space and resources with other coastal zone activities, which has resulted in the need for larger facilities and the relocation of operations to offshore areas. Moreover, the c...

Climate change is dramatically increasing the frequency and severity of marine heatwaves (MHWs) in the Mediterranean basin, strongly affecting marine food production systems. However, how it will shape the ecology of aquaculture systems, and the cascading effects on productivity, is still a major knowledge gap. The present work aims to increase our...

Epigenetic changes such as DNA methylation modifications at specific loci in the genome in response to environmental cues can appear long before the appearance of transcriptomic or other phenotypic changes with potential consequences for performance. Thus, epigenetic DNA methylation-based biomarkers hold great promise in aquaculture and conservatio...

Dissolved oxygen (DO) is one of the most critical parameters for aquaculture, as it is vital for all living organisms. The survival, growth and food intake of fish is directly affected by changes in DO concentration. Therefore, the systematic and continuous monitoring of DO is of crucial importance for proper production management. DO does not chan...

Environmental effects and, particularly, temperature changes have been demonstrated to influence the activity, function, and well-being of teleosts. Temperature may change seasonally in the wild, and in captivity under aquaculture operations. Moreover, climate change is expected to shift temperature profiles worldwide. MicroRNAs (miRNA) are importa...

The usefulness of acoustic telemetry on the study of movements, interactions, and behaviors has been revealed by many field and laboratory studies. The process of attaching acoustic tags on fish can, however, impact their physiological, behavioral, and growth performance traits. The potential negative effects are still unknown for several species a...

European sea bass is a species of great commercial value for fisheries and aquaculture. Rising temperatures may jeopardize the performance and survival of the species across its distribution and farming range, making the investigation of its thermal responses highly relevant. In this article, the metabolic scope, performance, and tolerance of juven...

Chronic Ulcerative Dermatopathy (CUD) is a disease that affects all cultured meagre when reared in facilities supplied with borehole water, resulting in ulceration of the skin overlying the lateral line canals. The aims of this study were (i) to describe the morphogenesis of the cephalic lateral line, (ii) to investigate the effect of the use of bo...

Epitheliocystis is a fish gill disease caused by a broad range of intracellular bacteria infecting freshwater and marine fish worldwide. Here we report the occurrence and progression of epitheliocystis in greater amberjack reared in Crete (Greece). The disease appears to be caused mainly by a novel Betaproteobacteria belonging to the Candidatus Ich...

Chronic discharge of surplus organic matter is a typical side effect of fish aquaculture, occasionally leading to coastal eutrophication and excessive phytoplankton growth. Owing to their innate filter-feeding capacity, marine sponges could mitigate environmental impact under integrated multitrophic aquaculture (IMTA) scenarios. Herein, we investig...

The histological process of gonadal differentiation, together with the endocrine changes of sex steroid hormones and some of their precursors, was studied in hatchery-produced greater amberjack Seriola dumerili from 101 until 408 days post-hatching (dph), with samplings conducted every 50 days. Histological processing showed that sex differentiatio...

Monitoring and understanding fish behavior is crucial for achieving precision in everyday husbandry practices (i.e. for optimizing farm performance), and for improving fish welfare in aquaculture. Various intelligent monitoring and control methods, using mathematical models, acoustic methods and computer vision, have been recently developed for thi...

Two potential candidate species for the Mediterranean aquaculture–the common dentex (Dentex dentex) and the sharpsnout seabream (Diplodus puntazzo)-are used in the present study in order to depict their genetic architecture for the first time. We have constructed the first linkage maps for both species using SNP markers derived from ddRAD sequencin...

The overall fish welfare in sea-caged European sea bass (Dicentrarchus labrax) was quantitatively assessed by adapting the Salmon Welfare Index Model (SWIM 1.0). In the model, a total of 16 operational welfare indicators in three segments (i) individual fish-based; (ii) fish-group specific; and (iii) sea cage environment-specific indicators were ev...

In this paper we present our initial findings from investigating the dampening of acoustic signals through dense fish layers, referred to as shadowing. These findings are based on measurements which were performed in the Mediterranean Sea and off the Norwegian coast using gilthead seabream and Atlantic salmon respectively. The paper also presents t...

Climate change is expected to have a drastic effect on aquaculture worldwide. As we move forward with the agenda to increase and diversify aquaculture production, rising temperatures will have a progressively relevant impact on fish farming, linked to a multitude of issues associated with fish welfare. Temperature affects the physiology of both fis...

This article reports on the thermal tolerance, metabolic capacity and performance of juvenile meagre (Argyrosomus regius) reared under three high water temperatures (24, 29 and 34 °C) for three months. The analysis includes the thermal effects on the growth performance, metabolism and physiology of meagre, including a range of molecular, haematolog...

Climate change poses increasing challenges to aquaculture, resulting in the need to develop appropriate tools to assess these challenges and support decision-making. We present ClimeGreAq, a software-based Decision Support System (DSS) co-created with stakeholders to support the adaptation of Greek aquaculture to climate change. The DSS is based on...

Biogenic films are very thin surface oils, frequently observed near aquaculture farms, that affect the roughness and the optical properties of the sea surface, making them visible in SAR and multispectral images. The purpose of this study is to investigate the potential of satellite SAR and multispectral sensors in the detection of biogenic oil fil...

Temperatures experienced during early ontogeny significantly influence fish phenotypes, with clear consequences for the wild and reared stocks. We examined the effect of temperature (17, 20, or 23 °C) during the short embryonic and yolk-sac larval period, on the swimming performance and skeleton of metamorphosing Gilthead seabream larvae. In the fo...

Finfish aquaculture in the Mediterranean Sea faces increasing challenges due to climate change, while potential adaptation requires a robust assessment of the arising threats and opportunities. This paper presents an approach developed to investigate effects of climate drivers on Greek aquaculture, a representative Mediterranean country with a lead...

The histological process of gonadal differentiation together with the endocrine changes of glucocorticoids and sex steroids was studied in hatchery produced greater amberjack ( Seriola dumerili ) from 101 until 408 days post-hatching. In the samplings, which were conducted every 50 days, no size dimorphism was observed between the sexes and sex rat...

Finfish aquaculture in the Mediterranean Sea faces increasing challenges due to climate change while potential adaptation requires a robust assessment of the arising threats and opportunities. This paper presents an approach developed to investigate effects of climate drivers on Greek aquaculture, a representative Mediterranean country with a leadi...

The target of this study was to use indigenous probiotic bacteria in the rearing of seabass larvae. A Phaeobacter sp. strain isolated from bonito yolk-sac larvae (Sarda sarda) and identified by amplification of 16S rDNA showed in vitro inhibition against Vibrio anguillarum. This Phaeobacter sp. strain was used in the rearing of seabass larvae (Dice...

An overall synchronization of morphological and physiological ontogenetic events of the digestive and antioxidant defence systems occurred in greater amberjack (Seriola dumerili) larvae reared under intensive (INT) or semi‐intensive (MES) conditions for 30 days. The first differentiations of the digestive channel took place at 3–4 days post‐hatch (...

For the large producers of farmed fish, the utilization of fish by-products as ingredients of food is important and thus their characterization, in terms of chemical composition and safety, becomes necessary. In this study, eleven trace metal concentrations in by-products (head, gills, guts, trimmings, bones and skin) of two Mediterranean farmed fi...

Fish-cage dysfunction in aquaculture installations can trigger significant negative consequences affecting the operational costs. Low oxygen levels, due to excessive fooling's, leads to decrease growth performance, and feed efficiency. Therefore, frequent periodic inspection of fish-cage nets is required, but this task can become quite expensive wi...

Dietary micronutrient supplementation can serve as skin health promotor to prevent from natural infections and can be applied to decrease the use of antibacterial agents and their impact on the environment. Such supplementation has indicated anti-inflammatory and antioxidant properties in farmed fish. In this study, dietary supplementation of zinc,...

Processing of fish in aquaculture generates considerable amounts of by-products that remain underused and/or unexploited. We evaluated the nutritive content of fish by-products (head, gills, intestines, trimmings, bones, and skin) from meagre and gilthead sea bream fish species reared in Greece in order to estimate their nutritional value for futur...

Members of the genus Seriola have been notable species for aquaculture production worldwide, with the greater amberjack Seriola dumerili being a prominent species, partly due to its cosmopolitan distribution. A prerequisite to sustainable aquaculture production is controlling reproduction in captivity, which has been lacking for greater amberjack....

During early animal ontogenesis, a plethora of small non-coding RNAs (sncRNAs) are greatly expressed and have been shown to be involved in several regulatory pathways vital to proper development. The rapid advancements in sequencing and computing methodologies in the last decade have paved the way for the production of sequencing data in a broad ra...

Four different wreckfish (Polyprion americanus) broodstock batches were maintained in research facilities under different photo and thermo-period conditions, one in Greece, the Helenic Center for Marine Research (HCMR, n = 3) and three in Spain: Instituto Español de Oceanografía (IEO, n = 13) in Vigo, Aquarium Finisterrae (MC2, n = 21) in A Coruña...

Sex-biased gene expression is the mode through which sex dimorphism arises from a nearly identical genome, especially in organisms without genetic sex determination. Teleost fishes show great variations in the way the sex phenotype forms. Among them, Sparidae, that might be considered as a model family displays a remarkable diversity of reproductiv...

Marine fish larvae and crustaceans need, during the first periods of larval life, to be fed with zooplankton reared with the use of microalgae (phytoplankton) and enriched with omega-3 fatty acids using specialized products. On the contrary freshwater fish can be fed directly with artificial feeds. Furthermore, one of the most difficult periods of...

Aquaculture is one of the fastest growing food sectors worldwide providing more than 50% of world fish consumption.Towards sustainable development, aquaculture ought to design and implement technical solutions for the efficient management of farms, thus improving fish performance and decreasing operational costs, human effort and environmental impa...

The present study identified and characterized six key genes involved in the hypothalamic-pituitary-interrenal (HPI) axis of gilthead sea bream (Sparus aurata), a commercially important European aquaculture species. The key genes involved in the HPI axis for which gene structure and synteny analysis was carried out, comprised of two functional form...

The effects of water temperature (15, 20 and 25 °C) on the stress response of European sea bass, Dicentrarchus labrax, were studied. Blood and water samples were collected prior and at 0.5, 1, 2, 4 and 8 h post-stress for hormonal and biochemical analysis. Water temperature affected the resting concentrations of all stress indicators examined, as w...

The present study aimed to compare effects of increasing chronic stress load on the stress response of European seabass (Dicentrarchus labrax) and gilthead seabream (Sparus aurata) to identify neuroendocrine functions that regulate this response. Fish were left undisturbed (controls) or exposed to three levels of chronic stress for 3 weeks and then...

The present study aimed to compare effects of increasing chronic stress load on the stress response of European seabass (Dicentrarchus labrax) and gilthead seabream (Sparus aurata) to identify neuroendocrine functions that regulate this response. Fish were left undisturbed (controls) or exposed to three levels of chronic stress for 3 weeks and then...

The framework provided by the Dynamic Energy Budget (DEB) theory allows the quantification of metabolic processes and the associated biological rates that are of interest for aquaculture, such as growth and feeding. The DEB parameters were estimated for farmed European sea bass (Dicentrarchus labrax), a species of major importance for the Mediterra...

The EU Common Fisheries Policy (CFP) reform establishes a gradual landing obligation for stocks for which catch limits are set, and in the Mediterranean for species with Minimum Conservation Reference Size. However, the landing obligation will not apply for species with scientific evidence of high survival rates. Discards estimates usually assume t...

Sex differentiation is a puzzling problem in fish due to the variety of reproductive systems and the flexibility of their sex determination mechanisms. The Sparidae, a teleost family, reflects this remarkable diversity of sexual mechanisms found in fish. Our aim was to capture the transcriptomic signature of different sexes in two protogynous herma...