Feeding habits of Paralabrax nebulifer (Serranidae) during reproductive and non-reproductive seasons in an adjacent area to Magdalena Bay, Baja California Sur, Mexico

The barred sand bass Paralabrax nebulifer is a commercially important fish off the west coast of Baja California Sur. To assess the diet of this species and variations as a function of sex and reproductive condition, 60 specimens were captured using traps during seven seasonal sampling trips from August 2016 to August 2018 in an adjacent area to Magdalena Bay, Baja California Sur, Mexico. The stomach contents of 50 specimens were obtained (23 males and 27 females). Sex was diagnosed by direct observation of the gonads. Based on the gonadosomatic index, hepatosomatic index, and histological analyses, the reproductive season of the barred sand bass was corroborated for August 2016, April, August, and September 2017, and August 2018, and the non-reproductive season was corroborated for November 2016 and March 2018. The Index of Relative Importance (IRI) was used to classify the main diet components, which comprised three fish species, seven crustacean species, and one mollusk species. According to the IRI, the South American pilchard Sardinops sagax and the red pelagic crab Pleuroncodes planipes were the prey that contributed the most (55%) to the barred sand bass diet. The ANOSIM showed that there were significant differences in the amount and type of prey consumed by sex; the SIMPER analysis revealed that the species contributing the most to differences between the sexes were S. sagax (16.58%), Euphylax dovii (15.95%), Stenocionops ovata (12%), and P. planipes (11.82%) for females. There were significant differences in the amount and type of prey consumed between types of reproductive season; the species contributing the most to differences between seasons were Anchoa spp. (27.76%), and P. planipes for non-reproductive season (22.67%), and S. sagax (11.08%) for reproductive season. The feeding strategy of the barred sand bass was that of a specialist carnivorous predator that fed mainly on the fish Sardinops sagax during the reproductive season, which supply the dietary nutritional requirements of the lipids HUFA (arachidonic acid, 20:4n-6; eicosapentaenoic acid, 20:5n-3; docosahexaenoic acid, 22:6n-3), nutrients required to achieve reproductive success.

ICTIOPARASITOLOGÍA MARINA EN EL SISTEMA DE AFLORAMIENTO DE LA CORRIENTE DE HUMBOLDT: DESAFÍOS PARA LA REVISTA NEOTROPICAL HELMINTHOLOGY

El Sistema de Afloramiento de la Corriente de Humboldt, definido como “a Large Marine Ecosystem”, se extiende a lo largo de la Costa Occidental de América del Sur, desde la zona Centro Sur de Chile (app. 42°S) hasta el Norte del Perú (4°S). Es uno de los mayores sistemas de afloramiento del mundo y responsable por los extraordinariamente altos niveles de producción. Es considerado un sistema clase 1, altamente productivo (>300 g·C/m2-año). Los altos valores de producción primaria de este sistema soportan las más grandes pesquerías a nivel mundial (Alheit & Bernal, 1993). Alrededor del 18-20% de las capturas mundiales provienen de este sistema, específicamente de pelágicos pequeños como anchoveta (Engraulis ringens Jenyns, 1842), sardina (Sardinops sagax (Jenyns, 1842)) y jurel (Trachurus murphyi Nichols, 1920). De un sistema de estas características deberá esperarse una alta diversidad biológica.

ICTIOPARASITOLOGÍA MARINA EN EL SISTEMA DE AFLORAMIENTO DE LA CORRIENTE DE HUMBOLDT: DESAFÍOS PARA LA REVISTA NEOTROPICAL HELMINTHOLOGY

El Sistema de Afloramiento de la Corriente de Humboldt, definido como “a Large Marine Ecosystem”, se extiende a lo largo de la Costa Occidental de América del Sur, desde la zona Centro Sur de Chile (app. 42°S) hasta el Norte del Perú (4°S). Es uno de los mayores sistemas de afloramiento del mundo y responsable por los extraordinariamente altos niveles de producción. Es considerado un sistema clase 1, altamente productivo (>300 g·C/m2-año). Los altos valores de producción primaria de este sistema soportan las más grandes pesquerías a nivel mundial (Alheit & Bernal, 1993). Alrededor del 18-20% de las capturas mundiales provienen de este sistema, específicamente de pelágicos pequeños como anchoveta (Engraulis ringens Jenyns, 1842), sardina (Sardinops sagax (Jenyns, 1842)) y jurel (Trachurus murphyi Nichols, 1920). De un sistema de estas características deberá esperarse una alta diversidad biológica.

Otolith δ18O and microstructure analyses provide further evidence of population structure in sardine Sardinops sagax around South Africa

Sardine Sardinops sagax is an ecologically and economically important Clupeid found off the entire South African coast that includes both coastal upwelling and western boundary current systems. Although the management of the sardine fisheries historically assumed a single, panmictic population, the existence of three, semi-discrete subpopulations has recently been hypothesized. We conducted otolith δ18O and microstructure analyses to investigate nursery habitat temperatures and early life growth rates, respectively, of sardine collected from three biogeographic regions around South Africa’s coast to test that hypothesis. Analyses indicated that for both summer- and winter-captured adults and summer-captured juveniles, fishes from the west coast grew significantly slower in water that was several degrees cooler than those from the south and east coasts. This suggests that mixing of sardines between regions, particularly the west and other coasts, is relatively limited and supports the hypothesis of semi-discrete subpopulations. However, the west-south differences disappeared in the results for winter-captured juveniles, suggesting that differences in early life conditions between regions may change seasonally, and/or that all or most winter-captured juveniles originated from the west coast. Further elucidating the interactions between South African sardine subpopulations and the mechanisms thereof is important for sustainable harvesting of this species.

Pilchard orthomyxovirus (POMV). I. Characterisation of an emerging virus isolated from pilchards Sardinops sagax and Atlantic salmon Salmo salar

An orthomyxo-like virus was first isolated in 1998 as an incidental discovery from pilchards Sardinops sagax collected from waters off the South Australian coast. In the following 2 decades, orthomyxo-like viruses have been isolated from healthy pilchards in South Australia and Tasmania. In 2006, an orthomyxo-like virus was also isolated from farmed Atlantic salmon Salmo salar in Tasmania during routine surveillance and, again, from 2012 onwards from diseased Atlantic salmon. Using transmission electron microscopy, these viruses were identified as belonging to the family Orthomyxoviridae. To further characterise the viruses, the genomes of 11 viral isolates were sequenced. The open reading frames (ORFs) that encode 10 putative proteins from 8 viral genome segments were assembled from Illumina MiSeq next generation sequencing (NGS) data. The complete genome of a 2014 isolate was also assembled from NGS, RNA-sequencing (RNA-seq) data, that included conserved motifs that shared commonalities with infectious salmon anaemia virus, rainbow trout orthomyxovirus and Influenzavirus A. The presence of 8 viral proteins translated from genome segments was confirmed by mass spectrometric analysis including 2 novel proteins with no known orthologs. Sequence analysis of the ORFs, non-coding regions and proteins indicated that the viruses had minimal diversity and hence were named pilchard orthomyxovirus (POMV), based on the fish host species of its first isolation. The low homology of POMV proteins with previously characterised orthomyxoviruses suggests that POMV is the first virus to be characterised from a new genus within the Orthomyxoviridae. To facilitate more rapid detection and subsequent diagnostic confirmation of POMV infections, TaqMan and conventional nested PCRs were designed.