Distribution Of Paralarvae Research Articles

Epipelagic abundance and distribution of paralarvae (Cephalopoda: Mollusca) in the Colombian Pacific: rainy periods 2001-2004

Despite their great ecological and economic importance, information on cephalopods is scarce, especially on their paralarvae, particularly in the Colombian Pacific Ocean (OPC). Therefore, their abundance and distribution in the periods 23.Jun-12.Jul.01, 27.Ago-15. Sep.01, 03-22.Sep.02, 01-21.Sep.03 and 18 .Sep-08.Oct.04 were evaluated. Organims were caught at the surface with a conical net (O = 50cm, length 1.85m, pore 363μm). The temperature and salinity data were obtained with a CTD probe. Ommastrephidae (66.3%), Ancistrocheiridae-Ancistrocheirus lesueuri (14.2%) (first specific paralarval record for the OPC), Cranchiidae (1.5%), Enoploteuthidae, Gonatidae, Octopodidae, Onycoteuthidae, and Pyroteuthidae (≤0.5%) were identified. Newly hatched paralarvae (≤2.0mm) covered the whole OPC, indicating its relevance as a spawning area, especially in neritic waters. The smaller size at hatching could be due to the higher temperatures in the OPC than in other latitudes of the American Pacific. The meso-scalar distribution could be mediated especially by the geostrophic eddy, the Equatorial South Current and the Colombian Current. El Nino-moderate perhaps influenced the exclusive appearance of Ommastrephidae during the period 03-22.Sep.02. The night predominance (83.2 vs. 16.8% day) was attributed to the paralarval vertical migrations. The variability of these findings could be related to the interannual environmental changes framed in the great environmental complexity of the OPC and other unweighted factors, such as food availability and predation.

Oceanographic influences on the distribution and relative abundance of market squid paralarvae (Doryteuthis opalescens) off the Southern and Central California coast

AbstractMarket squid (Doryteuthis opalescens) are ecologically and economically important to the California Current Ecosystem, but populations undergo dramatic fluctuations that greatly affect food web dynamics and fishing communities. These population fluctuations are broadly attributed to 5–7‐years trends that can affect the oceanography across 1,000 km areas; however, monthly patterns over kilometer scales remain elusive. To investigate the population dynamics of market squid, we analysed the density and distribution of paralarvae in coastal waters from San Diego to Half Moon Bay, California, from 2011 to 2016. Warming local ocean conditions and a strong El Niño event drove a dramatic decline in relative paralarval abundance during the study period. Paralarval abundance was high during cool and productive La Niña conditions from 2011 to 2013, and extraordinarily low during warm and eutrophic El Niño conditions from 2015 to 2016 over the traditional spawning grounds in Southern and Central California. Market squid spawned earlier in the season and shifted northward during the transition from cool to warm ocean conditions. We used a general additive model to assess the variability in paralarval density and found that sea surface temperature (SST), zooplankton displacement volume, the log of surface chlorophyll‐a, and spatial and temporal predictor variables explained >40% of the deviance (adjusted r2 of .29). Greatest paralarval densities were associated with cool SST, moderate zooplankton concentrations and low chlorophyll‐a concentrations. In this paper we explore yearly and monthly trends in nearshore spawning for an economically important squid species and identify the major environmental influences that control their population variability.

Distribution of paralarvae and small juvenile cephalopods in relation to primary production in an upwelling area off southern Brazil

Abstract Vidal, E. A. G., Haimovici, M., and Hackbart, V. C. S. 2010. Distribution of paralarvae and small juvenile cephalopods in relation to primary production in an upwelling area off southern Brazil. – ICES Journal of Marine Science, 67: 1346–1352. The distribution of paralarvae and small juvenile cephalopods sampled by a rectangular midwater trawl (opening area 8 m2) over the continental shelf off Cape Santa Marta Grande, southern Brazil (28°09′S–29°56′S) during spring 1989 is discussed. An intrusion of Brazil Current Tropical Water (22°C; 36.5) separates warm, less-saline water (22°C; 35.2) from cooler, more-saline water (15°C; 36.4). Prevailing northeasterly winds led to upwelling of South Atlantic Central Water over the shelf, promoting high Chl a concentrations. Three species constituted 99% of the 628 cephalopods collected: Illex argentinus (n = 540; 4–40 mm mantle length, ML), Argonauta nodosa (n = 46; 2–19 mm ML), and Loligo sanpaulensis (n = 42, 2–21 mm ML). Segregation of I. argentinus juveniles of similar size suggests school formation as small as 10 mm ML. The presence of mature males along with fertilized female A. nodosa indicates mating early in life. There was a consistent and direct link between high plankton production and high densities of juvenile cephalopods through a short and ecologically efficient food chain. The relationship between production, pycnocline intensity, and the density of paralarvae and juveniles revealed suitable conditions for survival and growth during the upwelling season.

Distribution of cephalopod paralarvae in relation to the regional oceanography of the western Iberia

The present study analyses the distribution of cephalopod paralarvae off the Portuguese coast. The effects of temporal and physical variables on Loligo vulgaris, Octopus vulgaris, sepiolid and ommastrephid abundances are analysed with generalized linear models. Their distribution patterns are discussed in relation to mesoscale features, including currents, thermal fronts and coastal upwelling cross-shelf transport, prevailing in the western Iberia upwelling system. Paralarvae of the neritic species occur during a considerably extended period of the year with two or three abundance peaks within the highly productive upwelling system of the western Portuguese coast and contrasting with the Gulf of Cadiz area. Temperature and upwelling were shown to be the most important variables in modulating seasonality and distribution of these paralarvae. The influence of the physical environment is particularly pronounced for the paralarvae of O. vulgaris, following distinct patterns according to the oceanography of the western Iberia and the Gulf of Cadiz systems. The paralarvae of oceanic species, which in many cases have their northern limit of distribution at these latitudes, were mainly found in the southern part of the sampling area. The distribution of these species indicates that the prevailing oceanographic features of the Gulf of Cadiz system, especially fronts, together with temperature act as boundaries to geographic dispersal, contributing to an area of high cephalopod biodiversity in the southern Portuguese waters.