Early Miocene mollusc and fish biodiversity at the Proto-Mediterranean–Paratethys marine corridor

<p>Marine biodiversity is controlled by depth, climate, and ocean connectivity. The early Miocene marine fauna of the proto-Mediterranean is particularly important because this is the time when the connection with the Indo-Pacific realm was disrupted , and the marine biodiversity hotspot shifted toward the southeast, marking the onset of a subtropical gradually oligotrophic regime in the proto-Mediterranean Sea. The Mesohellenic basin in particular, at the northern part of the proto-Mediterranean, was located at the intersection with the Paratethys epicontinental sea. Therefore, the fauna in this area was influenced by the conditions in both basins. In this study, we present the mollusc and fish fauna of the Aquitanian Mesohellenic basin and discuss its paleobiogeographic and evolutionary implications. Comparisons and assessment of faunal similarities of the proto-Mediterranean and adjacent provinces is carried out using ordination methods to treat available data from relevant publications and the Paleobiology Database (PBDB).</p><p>This research has been co-financed by Greece and the European Union (European Social Fund- ESF) through the Operational Programme “Human Resources Development, Education and Lifelong Learning 2014–2020” in the context of the project “Mollusc and fish migrations in the dynamic environments of the early to middle Miocene in the Mediterranean” (MIS 5047960). </p>

Application of the analysis of trace elements composition for calcified structures of fish to solve fundamental and applied scientific tasks: a review

Microchemical analysis of calcified structures of fish is a modern technique for determining the origin of fish species and ontogenetic reconstructions of their habitat that can be applied for such tasks as stocks separation in mixed samples, tracking of fish migrations, determining of spawning, feeding or wintering areas, differentiation of fish of artificial and natural origin, growth analysis, age evaluation, etc. The approach is based on analysis of trace elements concentration between the center and periphery of a calcified structure, or precise measurement of the elements and their isotopes concentration in certain sites of sample. The calcified structures most often used for analysis are otoliths, skeleton bones, scales, and also statoliths of lampreys or beaks and statoliths of cephalopods. Specifics of the method application are described with examples of its use for solving diverse tasks of fundamental and applied science, in particular in complex studies of biological resources in the Amur River basin.

Evaluating acoustic-trawl survey strategies using an end-to-end ecosystem model

Fisheries independent surveys support science and fisheries assessments but are costly. Evaluating the efficacy of a survey before initiating it could save costs. We used the NORWECOM.E2E model to simulate Northeast Atlantic mackerel and Norwegian spring spawning herring distributions in the Norwegian Sea, and we ran vessel transects in silico to simulate acoustic-trawl surveys. The simulated data were processed using standard survey estimation software and compared to the stock abundances in the ecosystem model. Three existing real surveys were manipulated to demonstrate how the simulation framework can be used to investigate effects of changes in survey timing, direction, and coverage on survey estimates. The method picked up general sources of biases and variance, i.e. that surveys conducted during fish migrations are more vulnerable in terms of bias to timing and changes in survey direction than during more stationary situations and that increased effort reduced the sampling variance.

Instead of the foreword

The present article is dedicated to the 90th anniversary of the foundation of the Department of Ichthyology and Hydrobiology in Saint-Petersburg State University, as well as to the formation of ichthyological school by talented scientist and bestow teacher Professor Nikolai Lvovich Gerbilcky. The results of fundamental works which were fulfilled during much time when using the principle of ecological histophysiological analysis laid by N.L. Gerbilsky are shown in this article. Also the results of the analysis of species adaptations connecting with the reproduction of fishes and with survival of its progeny when using this new method were presented. The basic principles of the biotechnology of fish reproduction in industrial conditions were created because of these results. The sphere of the principles of morphological-physiological analysis were expended and continued by following leaders of the Department and Laboratories – the schoolers and the followers of N.L. Gerbilsky. The mechanisms of hormonal regulation of fish’s gametogenesis were studied and the patterns of phase changes in the regulation and ecological – physiological staging of fish’s gametogenesis were opened by B.N. Kazansky. Fundamental investigations of osmotic and ionic regulation in different species of acipenserids and salmonids from the perspective of ecological morphological physiology when using present experimental methods leaded up to the creation of new direction in the study of fish osmoregulation and its adaptation to water with different salinity by L.S. Krayushkina and her pupils and colleagues. The mechanisms of regulation of the gametogenesis and the functions of sex gonads, the differentiation of fish sex and the influence of extremal factors on the process of gameto- and gonad genesis in different fishes were investigated by G.M. Persov and his Laboratory of Experimental Ichthyology. The use and the development of the principle of Gerbilsky’s method outside the Department by his pupils were presented: in the creation of the theory of functional basis of fish migrations, in the studies of endocrine regulation of reproductive cycle in acipenserids and salmonids by I.A. Barannikova and colleagues of her Laboratory. Structural and functional peculiarities of hypothalamic-hypophysial neurosecreting system of fishes were studied by A.L. Polenov. The continuation of traditional ruse to the analysis of different fish adaptations were demonstrated in the investigations of the ichthyologists at present time.