Nikolaos Mitrizakis

@article{valdivieso_development_2023,
title = {Development of epigenetic biomarkers with diagnostic and prognostic value to assess the lasting effects of early temperature changes in farmed fish},
author = {Alejandro Valdivieso and Núria Sánchez-Baizán and Nikos Mitrizakis and Nikos Papandroulakis and Francesc Piferrer},
url = {https://imbbc.hcmr.gr/wp-content/uploads/2022/11/2023-Valdivieso-3.pdf
https://linkinghub.elsevier.com/retrieve/pii/S0044848622010353},
doi = {10.1016/j.aquaculture.2022.738918},
issn = {00448486},
year = {2023},
date = {2023-01-04},
urldate = {2022-11-10},
journal = {Aquaculture},
volume = {563},
pages = {738918},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{georgopoulou_european_2022,
title = {European seabass show variable responses in their group swimming features after tag implantation},
author = {Dimitra G Georgopoulou and Eleftheria Fanouraki and Dimitris Voskakis and Nikos Mitrizakis and Nikos Papandroulakis},
url = {https://imbbc.hcmr.gr/wp-content/uploads/2022/09/2022-Georgopoulou-62.pdf
https://www.frontiersin.org/articles/10.3389/fanim.2022.997948/full},
doi = {10.3389/fanim.2022.997948},
issn = {2673-6225},
year = {2022},
date = {2022-09-01},
urldate = {2022-09-26},
journal = {Frontiers in Animal Science},
volume = {3},
pages = {997948},
abstract = {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 and behavioral attributes. Previous studies have attempted to shed light on the effects of tag implantation on fish, focusing mainly on fish growth and physiological parameters, and one or two behavioral properties mainly on the individual level. However, the effect of this procedure could also be expressed at the group level. This study investigated the short-term effects of dummy and active body-implanted acoustic tags on the group-level swimming performance of adult European seabass (
Dicentrarchus labrax
) using optical flow analysis. We studied four main swimming performance properties—group speed, alignment (polarization), cohesion, and exploratory behavior. To help in the interpretation of any detected differences, physiological stress-related parameters were also extracted. The results show that the tag implantation procedure has variable effects on the different swimming performance attributes of fish. Group cohesion, polarization, and the group’s exploratory tendency were significantly impacted initially, and the effect persisted but to a lesser extent two weeks after surgery. In contrast, group speed was not affected initially but showed a significant decrease in comparison with the control group two weeks post-surgery. In addition, the physiological parameters tested did not show any significant difference between the control and the treated group 14 days after the onset of the experiment. The findings suggest that the effect of tagging is non-trivial, leading to responses and response times that could affect behavioral studies carried out using acoustic telemetry.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{kourkouta_long_2021,
title = {Long lasting effects of early temperature exposure on the swimming performance and skeleton development of metamorphosing Gilthead seabream ( Sparus aurata L.) larvae},
author = {Chara Kourkouta and Alice Printzi and George Geladakis and Nikos Mitrizakis and Nikos Papandroulakis and George Koumoundouros},
url = {https://www.nature.com/articles/s41598-021-88306-4
https://imbbc.hcmr.gr/wp-content/uploads/2021/05/2021-Kourkouta-SciReports-31-1.pdf
},
doi = {10.1038/s41598-021-88306-4},
issn = {2045-2322},
year = {2021},
date = {2021-04-01},
urldate = {2021-04-27},
journal = {Scientific Reports},
volume = {11},
number = {1},
pages = {8787},
abstract = {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 following ontogenetic period, all fish were subjected to common temperature (20 °C). The critical swimming speed of metamorphosing larvae was significantly decreased from 9.7 ± 0.6 TL/s (total length per second) at 17 °C developmental temperature (DT) to 8.7 ± 0.6 and 8.8 ± 0.7 TL/s at 20 and 23 °C DT respectively (p textless 0.05). Swimming performance was significantly correlated with fish body shape (p textless 0.05). Compared with the rest groups, fish of 17 °C DT presented a slender body shape, longer caudal peduncle, terminal mouth and ventrally transposed pectoral fins. Moreover, DT significantly affected the relative depth of heart ventricle (VD/TL, p textless 0.05), which was comparatively increased at 17 °C DT. Finally, the incidence of caudal-fin abnormalities significantly decreased (p textless 0.05) with the increase of DT. To our knowledge, this is the first evidence for the significant effect of DT during the short embryonic and yolk-sac larval period on the swimming performance of the later stages.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{georgopoulou_tracking_2021,
title = {Tracking and Analysis of the Movement Behavior of European Seabass (Dicentrarchus labrax) in Aquaculture Systems},
author = {Dimitra G Georgopoulou and Orestis Stavrakidis-Zachou and Nikos Mitrizakis and Nikos Papandroulakis},
url = {https://imbbc.hcmr.gr/wp-content/uploads/2022/01/2021-Georgopoulou-FrontAS-83.pdf
https://www.frontiersin.org/article/10.3389/fanim.2021.754520},
doi = {10.3389/fanim.2021.754520},
issn = {2673-6225},
year = {2021},
date = {2021-01-01},
urldate = {2022-01-12},
journal = {Frontiers in Animal Science},
volume = {2},
pages = {79},
abstract = {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 this reason. Here, a tracking algorithm based on computer vision that extracts short trajectories of individual European seabass in both recirculating aquaculture systems and sea cages was developed using videos from network cameras. Using this methodology, parameters such as instantaneous normalized speed, travel direction and preference for the tank surface by European seabass could be quantified. When testing the sensitivity of this algorithm for detecting fish swimming variations under different husbandry scenarios, we found that the algorithm could detect variations in all of the abovementioned parameters and could potentially be a useful tool for monitoring the behavioral state of European seabass.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{samaras_allostatic_2018,
title = {Allostatic load and stress physiology in European seabass (Dicentrarchus labrax L.) and gilthead seabream (Sparus aurata L.)},
author = {A Samaras and C E Santo and N Papandroulakis and N Mitrizakis and M Pavlidis and E Höglund and T N M Pelgrim and J Zethof and F A T Spanings and M A Vindas and L O E Ebbesson and G Flik and M Gorissen},
url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85052204375&doi=10.3389%2ffendo.2018.00451&partnerID=40&md5=0029971a56b42d71f149780bf330f378},
doi = {10.3389/fendo.2018.00451},
issn = {16642392},
year = {2018},
date = {2018-01-01},
journal = {Frontiers in Endocrinology},
volume = {9},
abstract = {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 subjected to an acute stress test (ACT). Chronic stress impeded growth and decreased feed consumption in seabass, not in seabream. In seabass basal cortisol levels are high and increase with stress load; the response to a subsequent ACT decreases with increasing (earlier) load. Basal cortisol levels in seabream increase with the stress load, whereas the ACT induced a similar response in all groups. In seabass and seabream plasma a-MSH levels and brain stem serotonergic activity and turnover were similar and not affected by chronic stress. Species-specific molecular neuro-regional differences were seen. In-situ hybridization analysis of the early immediate gene cfos in the preoptic area showed ACT-activation in seabream; in seabass the expression level was not affected by ACT and seems constitutively high. In seabream, expression levels of telencephalic crf, crfbp, gr1, and mr were downregulated; the seabass hypothalamic preoptic area showed increased expression of crf and gr1, and decreased expression of mr, and this increased the gr1/mr ratio considerably. We substantiate species-specific physiological differences to stress coping between seabream and seabass at an endocrine and neuroendocrine molecular level. Seabass appear less resilient to stress, which we conclude from high basal activities of stress-related parameters and poor, or absent, responses to ACT. This comparative study reveals important aquaculture, husbandry, and welfare implications for the rearing of these species. © 2018 Samaras, Espírito Santo, Papandroulakis, Mitrizakis, Pavlidis, Höglund, Pelgrim, Zethof, Spanings, Vindas, Ebbesson, Flik and Gorissen.},
note = {Publisher: Frontiers Media S.A.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{lika_experimental_2015,
title = {Do experimental units of different scale affect the biological performance of European sea bass Dicentrarchus labrax larvae?},
author = {K Lika and M Pavlidis and N Mitrizakis and A Samaras and N Papandroulakis},
url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84926299929&doi=10.1111%2fjfb.12636&partnerID=40&md5=5403c1ba5a13116f63509dba87aeda78},
doi = {10.1111/jfb.12636},
issn = {00221112},
year = {2015},
date = {2015-01-01},
journal = {Journal of Fish Biology},
volume = {86},
number = {4},
pages = {1271--1285},
abstract = {The effects of different tank volumes (2000, 500 and 40l) on European sea bass Dicentrarchus labrax larval rearing, relating to growth, survival, quality and stress variables, were investigated. A dynamic energy budget (DEB) model was used to analyse the results. The hydrodynamics of the tanks exhibited differences, with the water currents in the 2000l tanks to be almost one order of magnitude stronger than those in the 40l ones. Important differences in fish growth were observed between small and large tank-rearing volumes, with the smallest tank resulting in the slowest growth. Based on the DEB model analysis, growth differences were related to feeding rates, with growth in the smaller tank limited by food availability. Differences in survival rates were not statistically significant among the tank-rearing volumes. The quality evaluation of the fry (in terms of swimbladder, jaw and skeletal abnormalities) showed differences, with the smallest tank having the highest percentage of deformed individuals. This could be attributed to both the feeding variances and the hydrodynamics in the tanks. No differences were observed in terms of whole-body cortisol at the two developmental stages; flexion, and when the larvae body was fully covered by melanophores; when analysis was performed. This indicates that the allostatic load exerted on fish of different groups was similar and inside the fish-coping abilities range, in terms of the cortisol response axis. The selection of the experimental scale is of importance, especially when the results are to be transferred and applied on an industrial scale. © 2015 The Fisheries Society of the British Isles.},
note = {Publisher: Blackwell Publishing Ltd},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{mylonas_reproduction_2013,
title = {Reproduction of hatchery-produced meagre Argyrosomus regius in captivity I. Description of the annual reproductive cycle},
author = {C C Mylonas and N Mitrizakis and M Papadaki and I Sigelaki},
url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84886398444&doi=10.1016%2fj.aquaculture.2013.09.009&partnerID=40&md5=fc22bf7e18df3784b789a65fb143610b},
doi = {10.1016/j.aquaculture.2013.09.009},
issn = {00448486},
year = {2013},
date = {2013-01-01},
journal = {Aquaculture},
volume = {414-415},
pages = {309--317},
abstract = {The aim of the present study was to monitor the reproductive cycle of a hatchery-produced meagre Argyrosomus regius broodstock. Four-year-old fish of a mean weight (±SD) of 5.1±1.1kg for females (n=7) and 4.6±0.7kg for males (n=6), were maintained under simulated natural photo-thermal regime and sampled between November 2010 and July 2011. Vitellogenesis began in March, when the first increase in oocyte diameter was observed. Fully vitellogenic oocytes of mean (±SEM) diameter between 561±23 and 621±9μm were observed between April and June. Two of the seven females spawned spontaneously in June, producing six major spawns of 390,000-940,000 eggs per day with fertilization success >97%. Vitellogenesis was associated with relatively low levels of testosterone (T) ranging between mean values of 0.036±0.01ngml-1 and 0.207±0.07ngml-1, and of 17β-estradiol (E2) ranging between mean values of 0.194±0.09ngml-1 and 0.473±0.12ngml-1. Spermiation also began in March, but only 33% of the fish produced significant amounts of milt to allow sperm quality evaluations. In May 100% of the fish were spermiating, and in July spermiation ceased almost completely. No significant changes were observed during the spermiation period (March-June) in sperm concentration (mean ranged between 18.9 and 31.5×109szoaml-1) or initial sperm motility (mean ranged between 44 and 80%). The mean duration of motility (mean ranged between 0.78 and 1.27min) was also stable during the reproductive season, with the exception of a significant decrease in May. Mean plasma T and 11-ketotestosterone (11-KT) levels in male meagre increased gradually during the year, reaching their spermiation season peaks in March (0.818ng11-KTml-1) or in May (0.263ngTml-1). The study demonstrated that gametogenesis proceeds normally in hatchery-produced meagre and under the influence of relatively low levels of sex steroid hormones. Although spontaneous spawning was observed for the first time in meagre maintained in captivity (2 of 7 females), the study demonstrated also that oocyte maturation is sporadic and inconsistent, and reliable spawning could be obtained using only exogenous hormones. Furthermore, it was shown that females failing to undergo oocyte maturation, maintain their vitellogenic oocytes in a viable condition without significant atresia for a period of at least 2months (April-June). These oocytes could potentially be induced to undergo maturation, ovulation and spawning at any time during this "post-vitellogenesis" period. © 2013 Elsevier B.V.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}

@article{mylonas_reproduction_2013-1,
title = {Reproduction of hatchery-produced meagre Argyrosomus regius in captivity II. Hormonal induction of spawning and monitoring of spawning kinetics, egg production and egg quality},
author = {C C Mylonas and N Mitrizakis and C A Castaldo and C P Cerviño and M Papadaki and I Sigelaki},
url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-84886377596&partnerID=40&md5=237d527a7e2831d820e80c1868708b9d},
year = {2013},
date = {2013-01-01},
journal = {Aquaculture},
volume = {414-415},
pages = {318 -- 327},
abstract = {The present study aimed at the development of an effective and efficient hormonal spawning induction method for meagre Argyrosomus regius, using controlled-release delivery systems loaded with gonadotropin-releasing hormone agonist (GnRHa). Three sets of spawning induction experiments were undertaken in the course of three years. In experiment 1, group spawnings were performed at different times during the reproductive period, in order to determine the most appropriate time for hormonal induction of spawning. Experiment 2 described in more detail the spawning kinetics of individual females induced to spawn at different times during the season, in order to obtain important information on spawning kinetics, batch fecundity and total fecundity in response to the hormonal treatment. In experiment 3, two similar broodstocks were used to obtain further production characteristics and monitor variations in egg/larval quality over the spawning period. The effective GnRHa doses used were 55-84μgGnRHakg-1 body weight in males and 46-92μgGnRHakg-1 in females. In general, successful spawning induction was achieved between early May and early June. Implantation with GnRHa induced spawning 2-3d after treatment and produced an average (±SD) of 12±5 spawns per broodstock or female over 3weeks, most of them over consecutive days. Batch fecundity was extremely variable (mean of 6631 to 104,409eggskg-1), with the largest batches occurring 3-4d after treatment, and very low fecundity after 1week from GnRHa treatment. As a result, the first 4 spawns of all spawning induction experiments constituted a mean of 75±13% of the total relative fecundity. Overall mean total relative fecundity was variable at 380,780±167,577eggskg-1. Evaluation of the ovaries after the cessation of spawning, demonstrated that the females still contained large numbers of oocytes in full vitellogenesis, and it is hypothesized that these fish could spawn further in response to a second GnRHa implantation. Fertilization success was very high in all spawning induction experiments, with the overall mean being 89±5%. Similarly, the produced eggs were of very high quality, based on the survival of the eggs during embryogenesis (>95%), hatching success (>99%) and larval survival 5d after egg collection (>87%), resulting in an overall larva survival of 73% of the total number of eggs spawned. These studies demonstrate that the GnRHa implants are an effective and efficient method for the induction of spawning in meagre, leading to the production of eggs of high fecundity and quality. © 2013 Elsevier B.V.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}