S. A. Evseenko

On the distribution of larvae and localization of spawning stocks of White Sea herring Clupea pallasii marisalbi

On the basis of ichthyoplankton surveys made in June 2004–2005 and 2007, June–July 2010, and July 2011 in these bays and beyond them (in open waters of the White Sea Basin and adjacent areas of the Gorlo) larvae of White Sea herring were absent. Principal aggregations of larvae are found in the Kandalaksha Bay in June 2004–2005 and 2007. In the Onega Bay and in the Dvina Bay surveyed in June 2007 abundance of larvae was ratter low and in June–July 2010 and July 2011 in these bays and beyond them (in open waters of the White Sea Basin and adjacent areas of the Gorlo) larvae of White Sea herring were absent. Within the Kandalasksha Bay, from year to year, there were two disconnected aggregations of larvae. The space between them was situated in the open part of the bay along the transect of the Chupa Estuary and the Umba Estuary. One of the aggregations of larvae occupied the tail of the bay, and the second aggregation occupied the ante-mouth and mouth areas of the Chupa Estuary. It is supposed that these aggregations result from spawning of two independent spawning groups of the White Sea herring spawning in isolated regions of the Kandalaksha Bay. Presence of the bulk of larvae of the White Sea herring within the limits of the Kandakaksha Bay and their almost complete absence at the boundary of the bay with the White Sea Basin and at the boundaries between the Onega Bay and the Dvina Bay and the Basin support the hypothesis on the absence of an exchange with larvae between stocks of the White Sea herring spawning in large bays of the White Sea. The larvae are retained within shallow waters of the Kandalaksha Bay by the system of two-layer water circulation in the areas of spawning of herring in bays and gulfs of the estuarine type. Their drift outside of the Onega Bay and the Dvina Bay may be delimited by frontal divides at their boundaries with the Basin.

Materials to the Revision of the Genus Dolichopteryx and Closely Related Taxa (Ioichthys, Bathylychnops) with the Separation of a New Genus Dolichopteroides and Description of Three New Species (Fam. Opisthoproctidae)

Brief descriptions and data on the distribution of 16 species belonging to the genera Bathylychnops, Ioichthys, and Dolichopteryx, including three new species (B. chilensis, D. andriashevi, and D. vityazi), are provided; a new genus Dolichopteroides is distinguished (D. binocularis Beebe, 1932, is designated as its type species). Their geographic distribution is considered, and suggestions about the bathybenthopelagic mode of life of its adult individuals are made. Fry I. kaskini SL 6.6 cm caught in the western part of the Indian Ocean and a large (SL approximately 30 cm) adult individual of mainly subtropical species B. brachyrhynchus from the Nasca Seamount (the southeastern Pacific) are first described and depicted.

Species composition and distribution of summer ichthyoplankton in Chupa Estuary (Kandalaksha Bay of the White Sea)

On the basis of ichthyoplankton surveys performed in July 2002 and June 2004–2005 in Chupa Estuary and adjacent waters of Kandalaksha Bay, species composition and distribution of eggs and larvae of fish were studied. Early stages of development of seven fish species were found in the composition of ichthyoplankton. The bulk of abundance of ichthyoplankton was formed of Clupea pallasii marisalbi larvae. It was shown that the sites of aggregation of larval C. pallasii marisalbi from June to July are constant and located in the central and preestuarine areas of Chupa Estuary. Possible routes of their passive migrations within Chupa Estuary and the adjacent water area of Kandalaksha Bay are considered. It is suggested that the drift of larvae beyond the estuary proceeds slowly, and after hatching they can long stay in the estuary concentrating in its central and preestuarine areas.

On the spatial distribution of larval White Sea herring (Clupea pallasii marisalbi) in estuaries of Kandalaksha Bay of the White Sea

According to results of layer-by-layer fishings performed in June 2006 in the Knyazhaya and Kolvitsa estuaries, data on the spatial distribution of larval White Sea herring Clupea pallasi marisalbi during the tidal cycle are provided. In these estuaries, the presence of a system of counter-currents that form a two-layer circulation was revealed. The surface current that is directed to the bay is traced to a depth of 2–4 m; below this, a current directed to the tail part of estuaries was recorded. It was established that larval herrings perform vertical migrations, as a result of which they can be freely drifted from inlets with a surface current and penetrate back from the adjoining water areas with a counter-current, which promotes a decrease in their drift in the open part of Kandalaksha Bay beyond shallow zones of juvenile feeding.

Early Life History Stages of Peacock Flounder Bothus lunatus (Bothidae) from the Western and Central Tropical Atlantic

Previously unknown larvae and poorly studied metamorphic and postmetamorphic stages of development of peacock flounder Bothus lunatus (Bothidae) with a length of 5.4 to 39.5 mm from the western and central tropical waters of the Atlantic Ocean are described, and their identification is substantiated. Small-and medium-sized larvae of this species (with a length of nearly 10 mm) at stages of pre-and postflexion, like all larvae of the genus Bothus at the corresponding stages of development, have a strongly flattened from the sides, moderately deep, and almost pigment-free transparent body; bear a long anterior ray in the dorsal fin; and have single melanophores in the end part of the body. They differ from larvae of other Atlantic species of the genus known at early stages of development in the shape of the anterior head profile, namely in the presence of a deep notch in front of the eyes. With growth, their body assumes a rounded shape. During metamorphosis of larval B. lunatus, the right eye shifts to the left side of the head through a slit formed during the separation of the origin of dorsal fin base from the cranium. This specific feature distinguishes them from larvae of the remaining species of the genus in which, during metamorphosis, the right eye passes to the left side through the hole in the head.

Distribution and routes of drift migrations in larvae of three species of flatfish Bothus (Bothidae) in open waters of the northern Atlantic

On the basis of large collections, comprehensive data on the distribution of larvae of three species of flatfishes of the genus Bothus (B. ocellatus, B. robinsi, and B. podas) in the northern Atlantic are provided, and the routes of their drift migrations are discussed. Special attention is focused on discussing problems of identification of larvae of the listed species and the specification of evidence on meristic characters of adult flatfishes of these species used for the diagnostics of their larvae. It is shown that larvae of two American species of Bothus carried out from the shelves to the system of western boundary currents are widely distributed in the northern Atlantic drifting in waters of the Northern Subtropical Gyre (NSG). Some of them reach the Azores, and some are drifted along the periphery of the circulation system of the NSG currents towards North America. Unlike larvae of American species, larvae of the eastern Atlantic B. podas perform no transatlantic drift migrations, and the area of their distribution is confined to the waters of the eastern Atlantic. Such differences in the extent of latitudinal passive migrations between B. podas and western Atlantic species are explained according to Torson (1965) by differences in temperature conditions during the drift of larvae of species under comparison that directly affect the decrease (during water temperature increase) or increase (at temperature decrease) of the pelagic phase in their development. The latitudinal drift of larval B. podas from West Africa westwards proceeds due to currents that gradually warm during their motion, which causes a decrease of the dates of their staying in the pelagial. The transatlantic drift of larval American Bothus spp. from North America eastwards is observed in gradually cooling currents, which leads to an increase in the duration and extent of their passive migrations.

On the morphology of the early life history stages of lanternfish genus Triphoturus (Myctophidae) and distribution of T. oculeum larvae in southeastern waters of the Pacific Ocean

Results of comparative analysis of specific features of morphology of larval lanternfishes of the Indo-Pacific genus Triphoturus based on materials from the southeastern part of the Pacific Ocean, northwestern Pacific, South China Sea, and the western part of the Indian Ocean, as well as on published data, are provided. Noticeable differences are shown in specific features of pigmentation of larval T. nigrescens (sensu Hulley, 1986) from different parts of the vast range of this species, that may be accounted for by its individual and/or geographic variation and by the collective pattern of this taxon. It is stated that it is necessary to use genetic data for the verification of the taxonomic status of the representatives of the genus. Morphological evidence in favor of the species isolation of T. oculeum and T. microchir based on larval materials is presented. The presence of three morphologically different forms of larval Triphoturus from the eastern Pacific differing in the pattern of body pigmentation that are identified with three nominal species of the genus Triphoturus—T. nigrescens, T. mexicanus, and T. oculeum—is confirmed. The study of specific features of distribution of larvae of these species in southeastern waters of the Pacific Ocean based on our own and published materials revealed the presence of larval T. mexicanus and T. oculeum off Peru, which is supported by data on the presence of adult individuals of both species here.

Distribution of the larvae of capelin Mallotus villosus and lesser sandeel Ammodytes marinus in the White Sea

The early developmental stages of capelin Mallotus villosus and lesser sandeel Ammodytes marinus were the major representatives of the fish larvae in the ichthyoplankton of the open waters of the White Sea in June 2007 and 2010 and in July 2010 and 2011. The larvae of these two species were widely distributed in the White Sea and have been registered in the large bays and in the other parts of the sea. The larvae of capelin and lesser sandeel were the most abundant in Onega Bay and in Dvina Bay and in Gorlo Strait of the White Sea; the larvae of lesser sandeel have also been found in the coastal waters of Kandalaksha Bay. The schooling of the larvae of these two species were characterized by a relatively permanent localization that referred to the spawning grounds; the shape and the location of the schoolings usually depend on the presence and configuration of the areas of the pronounced gradients of the hydrophysical parameters in these areas.

On species composition of ichthyoplankton of the Mid-Atlantic Ridge (South Atlantic)

Illustrated descriptions of the larval and/or juvenile fish of the following scarcely studied taxonomic forms are given: Tiluropsis (Halosauridae), Heteroconger sp. (Heterocongrinae), Lampanyctus alatus, Lampanyctus cf. crocodilus, Lampanyctus sp. 1, Loweina rara, Myctophum affine (Myctophidae), and Bregmaceros atlanticus (Bregmacerotidae). The problems of identifying of early development stages of these taxa are considered.

Effect of trophic conditions on the growth and abundance of larvae of herring Clupea pallasii marisalbi in areas of their mass aggregations in Kandalaksha and Onega bays of the White Sea

On the basis of materials collected during June 18–26, 2012, in three polygons in Onega (Ukhta Inlet) and Kandalaksha (Chupa and Knyazhaya inlets) bays of the White Sea, the effect of concentration and size-species structure of the zooplankton and of the amount of potential predators on the numbers and growth rate of larvae of the White Sea herring Clupea pallasii marisalbi are considered. The total numbers of zooplankton in Ukhta, Chupa, and Knyazhaya inlets (25041, 39162–76555, and 18459–33870 ind/m3, respectively) noticeably exceeds minimal values necessary for the growth and development of larvae. Correlation analysis of the size composition of larval herring and size-species composition of net mesoplankton indicates that food preferences of larvae of different size groups significantly differ. The growth rate of larvae in Kandalaksha Bay is 0.20–0.25 mm/day. A feedback between the numbers of larvae of the White Sea herring and hydromedusas was revealed: in Chupa Inlet at a greater concentration of jelly-bodied zooplankton, the numbers of larvae were considerably lower, and their reduction at 5 days turned out to be more significant than at a relatively low concentration of medusas in Knyazhaya Inlet. This indicates that food conditions are not always a single and decisive factor responsible for the formation of strong or weak-year classes of herring.