Egg production, spawning biomass and factors influencing recruitment of striped bass in the Potomac River and the upper Chesapeake Bay

Ichthyoplankton surveys in the Potomac River and Upper Chesapeake Bay were carried out in 1989 to estimate striped bass egg productions, age specific spawning biomasses of adult females, cohort-specific larval growth and mortality rates, and hatch dates of 8.0 mm larvae survivors. Possible consequences to recruitment of environmental factors were examined in 1989 and for data collected in 1987-1988. The temporal and spatial occurrences and distributions of eggs and larvae In both spawning areas are described and discussed in relation to environmental factors (temperature, rainfall, river discharge, pH, conductivity, zooplankton abundances) (PDF contains 319 pages

High temporal resolution sampling reveals reef fish settlement is highly clustered

Coral reef fish larvae settle on reefs predominantly at night around the new-moon phase, after an early developmental period spent in the pelagic environment. Most sampling is conducted across whole nights, and any studies that have examined the frequency of arrival within nights have typically been limited to coarse sampling time scales of 1–5 h. Here, we present results for arrival numbers of fish caught between dusk and midnight from light traps sampled every 15 min at an Indonesian coral reef, providing the finest temporal resolution for this type of study to date. A spatial analysis by distance indices analysis, adapted to temporal data, revealed clustering of reef arrival times for many species, with an increase in catches immediately after dusk dropping off towards midnight. Importantly, the timing of clusters differed among species, indicating that different factors determine the timing of arrival among taxa. Our results support the hypothesis that larval behaviour influences the timing of arrival at a coral reef for different fish species

The interrelation between temperature regimes and fish size in juvenile Atlantic cod (Gadus morhua): effects on growth and feed conversion efficiency

The present paper describes the growth properties of juvenile Atlantic cod (Gadus morhua) reared at 7, 10, 13 and 16 °C, and a group reared under “temperature steps” i.e. with temperature reduced successively from 16 to 13 and 10 °C. Growth rate and feed conversion efficiency of juvenile Atlantic cod were significantly influenced by the interaction of temperature and fish size. Overall growth was highest in the 13 °C and the T-step groups but for different reasons, as the fish at 13 °C had 10% higher overall feeding intake compared to the T-step group, whereas the T-step had 8% higher feeding efficiency. After termination of the laboratory study the fish were reared in sea pens at ambient conditions for 17 months. The groups performed differently when reared at ambient conditions in the sea as the T-step group was 11.6, 11.5, 5.3 and 7.5% larger than 7, 10, 13 and 16 °C, respectively in June 2005. Optimal temperature for growth and feed conversion efficiency decreased with size, indicating an ontogenetic reduction in optimum temperature for growth with increasing size. The results suggest an optimum temperature for growth of juvenile Atlantic cod in the size range 5–50 g dropping from 14.7 °C for 5–10 g juvenile to 12.4 °C for 40–50 g juvenile. Moreover, a broader parabolic regression curve between growth, feed conversion efficiency and temperature as size increases, indicate increased temperature tolerance with size. The study confirms that juvenile cod exhibits ontogenetic variation in temperature optimum, which might partly explain different spatial distribution of juvenile and adult cod in ocean waters. Our study also indicates a physiological mechanism that might be linked to cod migrations as cod may maximize their feeding efficiency by active thermoregulation

Egg development of scaled sardine Harengula pensacolae Goode & Bean (Pisces, Clupeidae)

Egg development of scaled sardine (Harengula pensacolae) was observed. The fertilized eggs were laid by mature adults in March 1, 1971. Some characteristics of fertilized eggs and plankton eggs are described. Plankton eggs collected during the summer season of 1969-70 suggest that the spawning area of this species is located in the region of Una Grande, Rio de Janeiro.Neste trabalho são apresentadas as observações sobre o desenvolvimento de ovos de sardinha cascuda (Harengula pensacolae). Os ovos foram fecundados ar tificialmente a bordo do N/Oc. "Prof. W.Besnard" na viagem de março de 1971, na região sul do Brasil. 1 - Os ovos são isolados e planctônicos. A forma e esférica com um pequeno glóbulo de óleo no vitelo. A membrana do ovo é incolor e sem estrutura na superfície. Os ovos têm espaço perivitelino bem amplo. 2 - O valor médio do diâmetro dos ovos é 1,638 mm com a distribuição de 1,48 a 1,72 mm. A média de diâmetro do glóbulo de óleo é 0,089 mm com a distribuição de 0,071 a 0,101 mm. A média do espaço perivitelino é de 0,90 mm. 3 - A época de desova desta espécie, baseada na coleta de ovos e larvas, vai de setembro a abril. 4 - A desova ocorre nas águas costeiras (não ultrapassa a linha de 65 m de profundidade) com temperatura de 19,20 a 26,97ºC em 10 m de profundidade com salinidade de 34,86 a 35,85‰, na região da Ilha Grande