Roxana De Silva-Dávila

UNUSUAL LARVAL GROWTH PRODUCTION OF NYCTIPHANES SIMPLEX IN BAHIA DE LA PAZ, BAJA CALIFORNIA SUR, MEXICO

Nyctiphanes simplex is one of the few neritic euphausiid species in the world. This species frequently dominates the nearshore waters of the Gulf of California, the transition zone of the California Current, and the eastern tropical Pacific off Ecuador and Peri. It has a high production in coastal and upwelling waters and plays an important role in the trophodynamics of these areas. This work examines the larval growth production (Pg) of Nyctiphanes simplex in Bahia de La Paz, Baja California Sur, Mexico. The data were collected during 7 oceanographic expeditions from February-August 1990. Except for August, larval growth production remained at high levels in the bay. Daily and annual growth production for both transects were estimated. The mean annual larval Pg value for the entire area was 195.7 mg-dw-m-3 yrl, the highest value recorded for the genus Nyctiphanes. The annual mean P:B ratio (defined as the ratio of annual production to average annual biomass for a particular species) for the bay was 35, using data representing mostly the youngest part of the population, which exhibits the highest growth rates (individuals < 6 mm). These values are related to the reproductive period of the species and to regional biological and oceanographic features present in this bay. We consider these values of larval Pg as an index that in Bahia de La Paz the production of Nyctiphanes simplex is comparable to that of upwelling regions and that the bay functions as a nursery and feeding area for many other species, such as sardines, whales, manta rays, and zooplankton.

Unusual Larval Growth Production of Nyctiphanes simplex in Bahía de La Paz, Baja California sur, México@@@Unusual Larval Growth Production of Nyctiphanes simplex in Bahia de La Paz, Baja California sur, Mexico

ABSTRACT Nyctiphanes simplex is one of the few neritic euphausiid species in the world. This species frequently dominates the nearshore waters of the Gulf of California, the transition zone of the California Current, and the eastern tropical Pacific off Ecuador and Peru. It has a high production in coastal and upwelling waters and plays an important role in the trophodynamics of these areas. This work examines the larval growth production (Pg) of Nyctiphanes simplex in Bahfa de La Paz, Baja California Sur, Mexico. The data were collected during 7 oceanographic expeditions from February-August 1990. Except for August, larval growth production remained at high levels in the bay. Daily and annual growth production for both transects were estimated. The mean annual larval Pg value for the entire area was 195.7 mg·dw·m-3 yr-1, the highest value recorded for the genus Nyctiphanes. The annual mean P:B ratio (defined as the ratio of annual production to average annual biomass for a particular species) for the bay was 35, using data representing mostly the youngest part of the population, which exhibits the highest growth rates (individuals < 6 mm). These values are related to the reproductive period of the species and to regional biological and oceanographic features present in this bay. We consider these values of larval Pg as an index that in Bahia de La Paz the production of Nyctiphanes simplex is comparable to that of upwelling regions and that the bay functions as a nursery and feeding area for many other species, such as sardines, whales, manta rays, and zooplankton.

Fish larvae from the Gulf of California to Colima, Mexico: An update

An updated taxonomic list of marine fish larvae from the Gulf of California to Colima, Mexico is presented. A total of 579 taxa belonging to 119 families, 256 genera, and 423 species were recorded. The list was compiled using 14 publications on fish larvae research (1974-2012), and the fish larvae identified from 315 samples collected with Bongo nets during 10 oceanographic cruises made from the Gulf of California to Bahia de Banderas, Mexico, from 2003 to 2007 (this study). The most important families in this study were the Myctophidae (28.3%), Engraulidae (25.0%), and Clupeidae (15.4%). The most abundant species were Cetengraulis mysticetus (18.2%), Benthosema panamense (13.9%), and Opisthonema libertate (12.7%). The compiled taxonomic list shows the addition of 296 new taxa to the previous list published 10 years ago, and also the need of an increase in the effort on the taxonomy of fish larvae forms not identified to species level.

Influence of the oceanographic dynamic in size distribution of cephalopod paralarvae in the southern Mexican Pacific Ocean (rainy seasons 2007 and 2008)

The southern Mexican Pacific Ocean presents seasonal changes related to the rainy season and Tehuano winds, which generate mesoscale processes affecting biological productivity and marine biodiversity. Size distributions of squid paralarvae collected in this region during the rainy season (July 2007 and May-June 2008) were analyzed in relation to regional oceanography. Samples were collected through oblique hauls, and CTD casts were used to determine the structure of the water column. Between surveyed periods, there were no significant changes in the water temperature at 10 m, but there were significant variations in the mixed layer depth (MLD). The number of taxa, community composition and total abundance of paralarvae were similar between periods. However, in July paralarvae ≤2.0 mm were distributed along the margins of cyclonic and anticyclonic eddies associated with high temperatures. In May-June, the MLD and high concentrations of chlorophyll-a (Chl-a) determined the presence of a group of oceanic paralarvae and another of coastal paralarvae, separated by an upwelling front. The percentage of recently spawned paralarvae (≤2.0) nearly doubled during this period as a result of increased coastal sampling and high concentrations of Chl-a, indicating a coupling of adult reproduction with regional productivity. In the absence of winds, the mesoscale oceanographic complexity generates gradients and a differential effect on the distribution, transport and survival of cephalopod paralarvae.

Reproductive Strategies of Sea Basses based on Larval Abundance in Magdalena Bay, Mexico, 1982-1986

Abstract We analyzed the reproductive strategies of four sea basses Paralabrax spp. based on larval abundance and sea surface temperature during a period affected by the El Nino of 1982–1983. Zooplankton samples were taken monthly in the Magdalena–Almejas lagoon complex of Baja California Sur, Mexico, from January 1982 to November 1986. Larvae of four sea bass species were recorded; those of the spotted sand bass P. maculatofasciatus were dominant, contributing 43% of total abundance. Barred sand bass P. nebulifer constituted 28% of the sampled larvae, goldspotted sand bass P. auroguttatus contributed 26%, and kelp bass P. clathratus made up 3%. During 1983–1984, the larval abundances of spotted sand bass and goldspotted sand bass decreased (by >50% and 90%, respectively), while the abundance of barred sand bass increased by nearly 25%. A seasonal larval abundance maximum for all species was recorded in summer and autumn, but a differential reproductive pattern inferred from larval abundance was determine...