Myctophid Species Research Articles

Distribution patterns of larval myctophid fishes in the transition region of the western North Pacific

We examined the species composition and horizontal distribution of myctophid fish larvae in the transition region of the western North Pacific during the early summer. In total, 4,760 myctophid larvae were collected at 44 stations; 18 species of myctophids from 15 genera were collected, and the 8 most abundant species accounted for >95% of larvae. The distribution patterns of these larvae were well defined by the hydrographic structures of the study area including the Oyashio and Kuroshio fronts, the Subarctic Boundary, and a warm core ring. The horizontal distribution patterns of the eight dominant species were categorized into three groups: northern transition water (Stenobrachius nannochir, Tarletonbeania taylori, and Lampanyctus jordani), southern transition water (Symbolophorus californiensis, Diaphus theta, and Nannobrachium regale), and Kuroshio (Myctophum asperum and Diaphus garmani). The Subarctic Boundary defined the distributions of the northern and southern transition-water groups. The importance of areas of western North Pacific transition water as spawning and nursery grounds for subarctic, transitional, and subtropical myctophid fishes was indicated by the relationship between the horizontal distribution patterns of larvae, juveniles, and adults and the physical oceanographic structures.

Dietary variation of the squid Moroteuthis ingens at four sites in the Southern Ocean: stomach contents, lipid and fatty acid profiles

Specimens of the onychoteuthid squid Moroteuthis ingens were collected from four sites in the Southern Ocean: Macquarie Island, the Falkland Islands, the Chatham Rise (New Zealand) and the Campbell Plateau (New Zealand). Spatial variations in diet among these areas were investigated using stomach contents and lipid and fatty acid profiles. Myctophid fish were prominent prey items at all sites, and the diet at New Zealand sites contained temperate myctophid species that were not identified at other sites. The diet at the Falkland Islands differed considerably from other sites due to the large proportion of cephalopod prey that had been consumed by M. ingens. This is likely to be due to the absence of key myctophids, such as Electrona carlsbergi, and the abundance of smaller squid such as Loligo gahi and juvenile M. ingens over the Patagonian Shelf. Stomach contents data could not be used effectively to determine dietary differences between the Chatham Rise and Campbell Plateau, largely due to differences in sample sizes between these sites. Lipid class and fatty acid profiles of the digestive gland indicated that the diet of M. ingens differed significantly between the Chatham Rise and Campbell Plateau, despite the relative proximity of these sites. We conclude from total lipid content that this was due to a reduction in food availability to M. ingens at the Campbell Plateau. The highly productive waters of the Subtropical Front pass over the Chatham Rise, whereas the Campbell Plateau is situated in less productive sub-Antarctic water. Differences in oceanographic conditions are likely to have driven dietary variations between these two sites.

COMPARATIVE FEEDING ECOLOGY OF SPINNER DOLPHINS (STENELLA LONGIROSTRIS) AND FRASER'S DOLPHINS (LAGENODELPHIS HOSEI) IN THE SULU SEA

AbstractFraser's and spinner dolphins are known to feed on mesopelagic prey, bur their diets and feeding ecologies have not been compared in areas where they are observed together. In this study we examined the stomach contents of both species caught incidentally in a driftnet fishery for tuna in the eastern Sulu Sea. Importance of prey items was determined using the percent occurrence, percent number, and volumetric methods. Mesopelagic fishes, particularly myctophids (mainly Ceratoscopelus warmingi, Diaphus spp. and Myctophum asperum), were the most important component in the diet of spinner dolphins, whereas in Eraser's dolphins, mesopelagic cephalopods (Abraliopsis, Onychoteuthis, Histioteuthis, and Chiroteuthis), and crustaceans (Notostomos elegans, Acanthephyra quadrispinosa, and Acanthephyra carinata) appeared to be equally important as the myctophid species. Fraser's dolphins appeared to feed preferentially on larger prey and had more diversified prey (Shannon's diversity index = 1.2) than spinner dolphins (diversity index = 0.9). Vertical distributions of the prey items summarized from published literature indicate that spinner dolphins forage in the upper 200 m and probably occasionally to as deep as 400 m, whereas Fraser's dolphins have a wider vertical foraging range, from near the surface to probably as deep as 600 m.

Feeding of diving predators and diel vertical migration of prey: King penguin diet versus trawl sampling at Kerguelen Islands

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 227:51-61 (2002) - doi:10.3354/meps227051 Feeding of diving predators and diel vertical migration of prey: King penguins¹ diet versus trawl sampling at Kerguelen Islands C. A. Bost1,*, T. Zorn1, Y. Le Maho1, G. Duhamel2 1Centre d¹Ecologie et Physiologie Energétiques, 23 rue Becquerel, 67087 Strasbourg Cedex 2, France 2Muséum National d¹Histoire Naturelle, Laboratoire d¹Ichtyologie Générale et Appliquée, 43 rue Cuvier, 75231 Paris Cedex 05, France *E-mail: charles.bost@c-strasbourg.fr ABSTRACT: The diving behavior and diet composition of King penguins were examined during summer 1995 at Kerguelen Islands. This was in relation to real-time estimations of diel prey availability during 2 sampling sessions totaling 10 d at sea. During daylight hours King penguins performed medium to deep dives of 120-250 m. At night, they dived no deeper than 60 m. Daytime, dusk and night-time sampling of prey was performed in the depth ranges corresponding to the depths of the penguins¹ dives in this study. The diversity in mesopelagic fish was found to be highest during the night at 0-50 m (15 vs 9 species during the day), and their number was up to 20-fold higher at these depths at night than during the day at the 150-250 m depth layer. The 3 myctophid species Electrona antarctica, Gymnoscopelus fraseri and G. braueri which were present in large sub-surface numbers during the night were virtually absent from the penguins¹ diet. The 2 species dominant in their diet, Muraenolepis marmoratus and Krefftichtys anderssoni (56.5 and 32.9% by number, 30.3 and 31.6% by biomass, respectively), were scarcely detected in the penguins¹ diving range during the night. In contrast, these 2 species, of which only the latter is bioluminescent, were significantly present during the day in the 0-300 m depth range (16.5 and 30.0% of the diurnal catches by number, respectively). In terms of biomass, these 2 prey types constituted only 6.3 and 12.6% of the total daylight trawls, which were dominated by the genus Protomyctophym (38.6% of the catches). The overlap between the penguins¹ diet and trawl content was the most significant with daylight sampled data. King penguin feeding success seems mostly dependent on deep dives during the day, despite lower prey availability than during the night. Ambient light levels, which were found to be higher at deeper depths (150-180 m) during the day compared to the sub-surface (0-60 m) at night-time, therefore appear to better determine King penguin foraging success than diel migration of prey to shallow depths. KEY WORDS: King penguins · Diet · Diel vertical migration · Myctophids · Foraging behavior Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 227. Online publication date: February 13, 2002 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2002 Inter-Research.

Humans and the Southern Elephant Seal Mirounga leonina

Southern elephant seal (Mirounga leonina) populations appear remarkably unaffected by interactions with humans. They are very tolerant of close human presence whilst they are ashore for pupping, mating and moulting. Their behaviour in close proximity to helicopter operations suggests disturbance of moulting male M. leonina is minimal. There is no evidence that M. leonina have been affected by persistent organic pollutants; and few M. leonina have been reported as having been injured or killed by interactions with fishery gear. The number of prey species common to their diet and commercial fisheries in the Southern Ocean are few; but one commercial squid species, Martialia hyadesi, accounted for as much as 94% of the biomass consumed by M. leonina. Two harvested commercial squid species (Mar. hyadesi and Todarodes filippovae) were found in the stomachs of M. leonina; and some other squid species (Alluroteuthis antarcticus, Brachioteuthis spp., Gonatus antarcticus, Histeoteuthis spp., Kondokovia longimana, Moroteuthis ingens, Mor. knipovitchi, Pholidoteuthis boschmani and Psychroteuthis glacialis) have potential as commercial catch too. There is cause for concern if a future directed fishery for any of these species escalates or the by-catch of Mar. hyadesi and T. filippovae in the Illex and Nototodarus fisheries increase. There is also concern if fin-fish fisheries expand and take more of those species already taken by both M. leonina and fisheries. These species are benthic (Notothenia squamifrons), benthopelagic (Dissostichus eleginoides and Champsocephalus gunnari) and, perhaps most importantly, the pelagic myctophid species (e.g., Electrona carlsbergi).

Growth of larval and juvenile Diaphus theta (Pisces: Myctophidae) in the transitional waters of the western North Pacific

Diaphus theta is one of the most common myctophid fish species in the subarctic and transitional waters of the North Pacific. The growth of larval and juvenile D. theta was investigated using sagittal otolith increment analysis of specimens caught in transitional waters of the western North Pacific. Samples taken over a 24-h period demonstrated that otoliths exhibited daily growth cycles, allowing accurate determination of age. Calcification of the incremental zone of otoliths took place only at night, suggesting that the formation cycle of the increment of juvenile D. theta was different from that of shallow-water fishes and would be related to their diel vertical migration. The relationships between standard length (SL) and daily growth increment (D) were expressed as linear equations: SL = 2.65 + 0.141D (r 2 = 0.942) for larvae of 5.1–9.6 mm SL and SL = 3.54 + 0.129D (r 2 = 0.933) for juveniles of 13.7–27.6 mm SL. The growth rates were 0.14 mm d−1 in larvae and 0.13 mm d−1 in juveniles; this is slow compared with tropical or subtropical mycto-phid species, in which growth occurs at about twice these rates. The larval period, including the metamorphic stage, was long compared with species at lower latitudes and was estimated to be 71 days. The slow growth rate and long period of larval stage of D. theta would be the life history pattern of high-latitudinal species adapted to a low-temperature habitat.

High abundance of larval rockfish over Cobb Seamount, an isolated seamount in the Northeast Pacific

The larval fish community in the region of Cobb Seamount (500 km west of Oregon) is dominated by myctophid species commonly encountered in the subarctic North Pacific. However, during a survey in June 1992, the ichthyoplankton community within 30 km of the seamount summit was almost completely dominated by larvae of various rockfish (Sebastes) species. Given their very small size (and hence very young age) and the fact that they occurred only rarely in samples collected > 30 km from the seamount summit, we conclude that these Sebastes larvae were produced locally over Cobb Seamount. Previous studies have shown that the Cobb fish fauna is dominated by various Sebastes spp. and that, unlike other fish present on the seamount, the rockfish populations may be self‐recruiting. We suggest that a persistent clockwise (i.e. downwelling) eddy, consistent with a stratified Taylor cone, plays a critical role in retaining larval rockfish over Cobb Seamount and may contribute to the process of self‐recruitment. The key to the success of rockfish on Cobb and other shallow Northeast Pacific seamounts seems to be linked to their viviparous life history.

Predation on myctophids by the squid Moroteuthis ingens around Macquarie and Heard Islands: stomach contents and fatty acid analyses

The diet of the sub-Antarctic onychoteuthid squid Moroteuthis ingens was assessed using stomach contents analyses and fatty acids as dietary tracers. The contents of 54 stomachs (50 from squid collected near Macquarie Island and 4 from squid collected near Heard Island) were examined visually, and prey remains were identified to species level where possible. Myctophid fish were the most common prey item in the stomach contents of M. ingens and were identified in 59% of stomachs. In total, teleost fish remains were found in 96% of stomachs. The lipid class and fatty acid profiles of the digestive gland and mantle tissue were analysed for 5 to 6 squid from each area, in addition to 4 stomach fluid samples taken from Heard Island animals. Mantle tissue was low in lipid, and contained high concentrations of phospholipids and polyunsaturated fatty acids. Digestive gland tissue had a high lipid content, with a mean value of 26.8 ± 12.9% wet mass in Macquarie Island squid and 41.7 ± 8.5% wet mass in Heard Island squid, and was rich in triacylglycerol (TAG) and monounsaturated fatty acids (MUFA). Stomach fluid generally contained high concentrations of TAG, although 1 sample was high in wax ester. Stomach fluid was also characterised by high MUFA con- centrations. The digestive gland of M. ingens grouped with the fatty acid profile of stomach fluid and some myctophid species in cluster analysis and multidimensional scaling, and appears to be a source of fatty acid dietary tracers. Thus the fatty acid profile of the digestive gland supports findings from stomach contents analyses that myctophids, particularly TAG-rich species, are an important prey group of M. ingens at Macquarie and Heard Islands. This combination of techniques has a potential to increase our knowledge of the feeding ecology of squids in the Southern Ocean.

Age and growth of Electrona antarctica (Pisces: Myctophidae), the dominant mesopelagic fish of the Southern Ocean

Numerically and in biomass, the lanternfish Electrona antarctica is the dominant fish in the vast pelagic region of the Southern Ocean bounded on the north by the Antarctic Convergence and in the south by the Antarctic continental shelf. It is an important krill predator, and in turn is important in the diets of flighted and swimming seabirds. Further, it is the southernmost and coldest-dwelling representative of the globally distributed fish family Myctophidae. The present study was undertaken to estimate the species' growth rate and average life span, to incorporate the information in a basic energy budget, and to compare the growth of E. antarctica with more northerly confamilials. Fishes were aged using primary growth increments that were resolved on sagittal otoliths using three sequential techniques: thin-section grinding and polishing, etching, and scanning electron microscopy (SEM). Based on increment width (0.8 to 1.2 μm), continuity, and previous studies on confamilials, the microincrements were assumed to be deposited on a daily basis. Montages of SEM photomicrographs were constructed for each sagitta to allow the daily rings to be counted over the entire life span of 31 individuals representing the entire size range of the species. Results suggest a larval stage of 30 to 47 d and a maximum life span of 3.5 yr, with females growing faster than males in the last 1.5 yr of life and reaching a larger maximum size. Construction of a simple energy budget using the best information available suggests that a surplus of energy is available to support the observed growth rates (0.05 to 0.07 mm d−1). The results of the present study contrast markedly with previous estimates of an 8 to 11 yr maximum age for E. antarctica. These results provide important data addressing the ecology and population dynamics of the pelagic Antarctic ecosystem. E. antarctica is the end-member species in the continuum of vertically migrating myctophids that extend from the equator to the polar circle. Its growth rate is consonant with that of all other myctophid species examined using primary growth increments to determine age. The present study, in conjunction with earlier studies, suggests that growth rates of mesopelagic species are far higher than previously thought.

Fish prey of fur seals Arctocephalus spp. at subantarctic Marion Island

The analysis of scats collected between 1989 and 1995 from the two fur seal species resident on subantarctic Marion Island, Arctocephalus gazella and A. tropicalis, showed that they fed predominantly on fish of the family Myctophidae (lanternfishes). Scat composition (prey species, abundance) was very similar for the two species. The seven species of myctophids that formed numerically 90 and 86% of the scat composition for A. gazella and A. tropicalis, respectively, all showed seasonal fluctuations in their contribution to seal diets. Electrona carlsbergi, E. subaspera, Metelectrona ventralis and Gymnoscopelus fraseri increased in winter in both species of fur seals, whereas Gymnoscopelus piabilis, Protomyctophum choriodon and P. tenisoni showed the opposite trend. Seal diets overlapped substantially with those of the king penguins (Aptenodytes patagonicus) resident on Marion Island, but no evidence for competitive exclusion could be found between these two major warmblooded consumers of marine resources at the Prince Edward Islands.

Origin of the monoene fats in the lipid of midwater fishes:relationship between the lipids of myctophids and those of their prey

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 168:21-33 (1998) - doi:10.3354/meps168021 Origin of the monoene fats in the lipid of midwater fishes: relationship between the lipids of myctophids and those of their prey Hiroaki Saito*, Masakazu Murata Laboratory of Lipid Chemistry (Lipid Chemistry Section), National Research Institute of Fisheries Science, Ministry of Agriculture, Forestry and Fisheries, Fuku-ura, Kanazawa-ku, Yokohama-shi 236, Japan *E-mail: hiroakis@nrifs.affrc.go.jp ABSTRACT: The lipid and fatty acid composition of the total lipids in the tissues (whole animal excluding stomach contents) and the stomach contents of 13 myctophid species living in the mesopelagic zone were analyzed. Triacylglycerols (TAG) were the dominant deposit lipids in 10 myctophid species, while wax esters (WE) were found to be the major neutral lipids in 3 non vertically migratory species. Lipids from the myctophid stomach contents were determined to contain mixtures of WE and TAG. Monoenoic acids and alcohols were the major fatty components in both the TAG and the WE of the lipids from the tissues and stomach contents of all of the specimens examined. Lipid classes in the stomach contents originating from prey were different from those in myctophid tissues, but the level of monoenes in stomach content lipids was very similar to those in the tissue lipids. This finding suggests that myctophids may transfer dietary lipids to specific lipid classes, without biosynthetic modification such as carbon chain elongation or desaturation. KEY WORDS: Myctophidae · Monoene · Deep-sea fish · Food chain · Fish oil · Lipid class · Fatty acid composition · Wax ester · Triacylglycerol · Monoenoic fatty acid Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 168. Publication date: July 09, 1998 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1998 Inter-Research.

Fish and squid in the diet of king penguin chicks, Aptenodytes patagonicus, during winter at sub-antarctic Crozet Islands

The diet of king penguins, Aptenodytes patagonicus, rearing chicks was studied during three consecutive austral winters (1990, 1991 and 1992) at Crozet Islands. The mean stomach content mass of the 47 samples was 503 g. Percentages of wet and reconstituted masses showed that both fishes (66 and 36%, respectively) and squid (34 and 64%) are important components of the winter diet. Juveniles of the demersal onychoteuthid squid Moroteuthis ingens form the bulk of the cephalopod diet, and this was the main prey by reconstituted mass (57%). Myctophid fish (lantern-fishes) accounted for most of the fish diet, constituting together 32% by mass. The three main species of myctophids eaten in summer by king penguins were either very rare in winter (Electrona carlsbergi) or accounted for a smaller proportion of the diet (Krefftichthys anderssoni = 1.5% by mass and Protomyctophum tenisoni = 4.6%). Five other myctophids, which are rarely consumed in summer, contributed 24% of the diet by mass in winter (Gymnoscopelus piabilis = 18.1%, Lampichthys procerus = 2.4%, G. nicholsi = 1.3%, and Metelectrona ventralis and Electrona subaspera = 1.0%). The greater diversity of prey in winter suggests a more opportunistic feeding behaviour at a time probably marked by a change in prey availability. Both the known ecology of the fish and squid prey and the barely digested state of some items suggest that in winter breeding adults forage in the outer shelf, upper slope and oceanic areas in the close vicinity of the Crozet Islands to feed their chicks. Finally, using king penguins as biological samplers, the present work provides novel data on the previously unstudied mesopelagic/epibenthic marine community in waters surrounding the Crozet Islands. Seventeen myctophid fish have been identified to species level. These include several poorly known species in the southern Indian Ocean. The occurrence of small, nearly intact, cephalopods in the diet of king penguins suggests that spawning grounds of four squid species may be located near the Crozet Archipelago.

Prey composition and daily rations of myctophid fishes in the Southern Ocean

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 134:1-14 (1996) - doi:10.3354/meps134001 Prey composition and daily rations of myctophid fishes in the Southern Ocean Pakhomov EA, Perissinotto R, McQuaid CD The feeding ecology of myctophids was studied using data collected during 5 South African scientific cruises to the Southern Ocean from 1985 to 1995. A total of 362 specimens, comprising 36 species, were analyzed for gut contents. Myctophid biomass levels, estimated from Bongo net tows, are among the lowest yet recorded for the Southern Ocean. Peak biomass levels were associated with the main frontal zones and with a permanent polynya region in the Lazarev Sea. Results show that all myctophid species are opportunistic mesozooplankton feeders exhibiting a high degree of overlap in their food spectrum and consuming primarily the most abundant species of copepods, euphausiids, hyperiids and pteropods. Daily rations were estimated using 3 different approaches and ranged from 0.2 to 4.4% of dry body weights. Generally, the daily food intake was equivalent to 0.5 (lower mean) to 2.9 (upper mean) of dry body weight for Antarctic and subantarctic species, and between 1.2 and 3.8% for temperate and subtropical species. Antarctic krill, Euphausia superba, was usually poorly represented in the stomachs of all but 1 myctophid species. The results of this study therefore do not support the hypothesis that krill plays a major role in the feeding ecology and budget of myctophids. Myctophid fishes . Antarctica . Feeding . Daily ration Full text in pdf format NextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 134. Publication date: April 25, 1996 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1996 Inter-Research.

Bioluminescence of myctophid and stomiiform fishes is not due to bacterial luciferase

AbstractA recent report by D. Foran proposes that bioluminescence of myctophids and some stomiiform fishes is due to bacterial symbionts in their photophores, based on positive hybridization of bacterial luminescence (lux) gene probes to DNA from muscle and skin of myctophids and stomiiforms and in situ hybridization. Previous microscopic studies have not revealed the presence of bacteria in these fishes, and bioluminescence of myctophids has been attributed to a coelenterazine‐based system. We have investigated this finding by assay of bacterial luciferase and by lux hybridization to DNA from photophores and control samples in order to determine whether bacterial symbionts or bacterial lux genes are present in these fishes. Results of enzyme assays of photophores from six species of myctophids and two species of stomiiforms show bacterial luciferase activity ranging from 0 to 7 × 105 quanta sec−1 mg wet weight−1. The highest levels detected were 3–4 orders of magnitude less than the activity of luminous bacteria and symbiotic light organ extracts, and were less than or equal to the activity of gut homogenates, which were up to tenfold higher than the highest photophore activities. Hybridization with lux probes did not detect lux sequences in photophore DNA from three species of myctophids and three species of stomiiforms. We find no evidence that bacterial luciferase is the source of luminescence in myctophid and stomiiform light organs.

Aspects of horizontal distribution and diet of myctophid fish in the Arabian Sea with reference to the deep water oxygen deficiency

Abstract Horizontal distribution of myctophid fishes were studied from two transects in the Arabian Sea in 1987. Species numbers exhibited a south-north decline in diversity, with only half of the fish taxa occupying the northeastern region. Diaphus arabicus was the dominant species both in the south and north. All recorded myctophid fish species migrate in a diel pattern, residing during daytime at depths of extremely low oxygen levels ( 2 1 −1 ) and foraging in the oxygen-rich surface layer at night. Feeding patterns were determined for the six most abundant myctophid species. All species appeared to be opportunistic predators that prey on a comparatively narrow food spectrum consisting principally of small to medium sized copepods. Numerically, non-calanoid copepods (with Oncaea conifera and O. venusta dominating) made up to 70% of the diet of D. arabicus and Bolinichthys longipes . Of the 26 calanoid copepod species identified from the six myctophid taxa, the genera Euchaeta, Pleuromamma and Candacia generally dominated in the stomachs, with P. indica constituting between 21 and 95% (by numbers) of the calanoid copepod prey.

Resource-partitioning and predation impact of a low-latitude myctophid community

This study, based on data collected during summer 1985 in the eastern Gulf of Mexico, examined the degree of overlap in two prime niche parameters, space and food, in 17 of the most abundant myctophid species which inhabit the epipelagic zone at night. Cluster-analyses of vertical distribution information and diet characteristics revealed that while large groups of species overlapped (>60%) in either vertical distributions or diet, when both niche parameters were considered together, little interspecific or intraspecific (size class) overlap occurred. Our data suggest that for myctophids trophic competition is reduced through resource-partitioning, although with considerable overlap at niche boundaries. Niche separation presumably is the result of competition during the evolution of the ecosystem and is maintained presently as “diffuse competition”: the effect on a species of the combined competition from all other species at that trophic level. We suggest that the large degree of niche overlap enables the “packing” of over 50 myctophid species in the epipelagic zone at night. Our calculations indicate that myctophid predation nightly removes 2% of the zooplankton biomass. Myctophid predation is selective in that greatest pressure is on certain size classes and types of prey (copepods, ostracods and euphausiids). In the case of copepods, impact is greatest on the larger, more mature stages and hence on the breeding population. It is estimated that myctophids account for at least one-third of the daily production of zooplankton removed from the epipelagic zone by micronekton in the eastern Gulf.

Otolith microstructure and growth patterns during the early life history of lanternfishes (family Myctophidae)

The microstructure of the central part of the sagittal otoliths of 55 myctophid species belonging to 27 genera of lanternfishes was compared by means of light and scanning electron microscopy. Multiple primordia were found in the nuclei of all otoliths. In most species and genera a symmetrical pattern of accessory primordia (AP) was observed: they were located along the same growth increment, which indicates simultaneous formation. A clustered pattern of AP was found only in species belonging to the tribe Gymnoscopelini: AP occurred at several growth increments, which indicates that they developed sequentially. The growth increments formed after the formation of clustered AP revealed a sectorial otolith structure, i.e., growth increments were not continuous but separated by radial discontinuities. The pattern and time of formation of AP were found to influence the relationship between otolith diameter and fish length in the Myctophidae. The formation of numerous AP concurrently with transformation of the larva led to a dissociation of fish growth from otolith growth. When AP appeared simultaneously but before transformation, the allometric relationship between otolith size and fish length was not disrupted by this process. Sequential formation of AP considerably before transformation, which occurred only in the Gymnoscopelini, led to an isometric relationship between fish size and otolith size. The potential importance of the AP pattern as a distinguishing character for myctophid larvae is considered to be greatest in the Gymnoscopelini, as these growth centers, in the form of external protrusions, were evident over a wide range of sizes from small larvae to early juveniles.

Distribution of Myctophidae (Pisces, Myctophiformes) during the four seasons in the mid North Atlantic

The distribution, temperature, and size ranges of 60 species of myctophids in the North Atlantic between 55°N and 24°N along approximately 30°W are recorded for the four seasons. The general zoogeography and migration is discussed. Faunal groups of species, faunal borders, and transition zones near 50°N, 41 °N, and 29°N for myctophids are distinguished and discussed.

Otolith microstructure and early ontogeny of a myctophid species Benthosema pterotum.

The correlation between otolith microstructure and early ontogeny was studied with the larvae, juveniles and adults of a myctophid species Benihoserna pterotum collected in Kagoshima Bay, southern Japan. From the width and shape of rings, the otolith structure was divided into the inner, middle, and outer zones surrounding a nucleus. Each zone had a different relationship between the standard length and otolith radius. The rapid change of photophore formation and melanophore pattern corresponded to the latter half of middle zone, and their completion to the start of outer zone. Considering the first half of middle zone to reflect the initiation event of metamorphosis, the inner, middle, and outer zones were correlated with larval, metamorphic, and juvenile to adult stages, respectively. The daily periodicity of ring formation was tested by tracing cohorts having different modes of body size, but the expected results could not be gained.

Diaphus pallidus sp.n., a new lanternfish from the Gulf of Aden (Pisces, Myctophidae)

A new myctophid species, Diaphus pallidus sp.n., was captured in the Gulf of Aden. The species can be distinguished from most of its congeners by the high number of dorsal fin rays and low number of gill rakers. It can be distinguished from D. lucidus (Goode & Bean) by the form of the operculum and by the situation of some of the body photophores.