Effects of plant density and the number of emitters on plant growth and nitrate concentration in spinach cultivated in substrate

The effects of plant density and the number of emitters per Styrofoam box on plant growth and nitrate (NO3-) concentration were evaluated in spinach (Spinacia oleracea L. cv. Tapir). Spinach seedlings were transplanted at 45 days after emergence into Styrofoam boxes filled with the substrate and were grown during winter in an unheated greenhouse with no supplemental lighting. The experiment was carried out with four treatments, including two plant densities (160 and 280 plants/m2) and two number of emitters per Styrofoam box (4 and 8 emitters). Each planting box was irrigated daily and fertigated with a complete nutrient solution. Shoot dry weight was not affected by plant density. However, yield increased with plant density and emitter number. Leaf-blade NO3- concentration was not affected by the interaction between plant density and number of emitters, but petioles NO3- concentration was greater in treatment with 160 plants/m2 and 8 emitters. Although leaf-blade NO3- concentration was not affected by plant density, it decreased with the number of emitters. On the other hand, petiole NO3- concentration was not affected by plant density or number of emitters. Leaf-blade NO3- concentration ranged from 3.2 to 4.1 mg/g fresh weight, occurring the highest value in the treatment with 280 plants/m2 and 4 emitters. Petiole NO3- concentration ranged from 3.5 to 5.3 mg/g fresh weight, values that were higher than allowed by EU regulation.

Effects of flow regulation in the life-cycles of a mediterranean cyprinid species, the Iberian chub (Squalius carolitertii Doadrio, 1987)

Streamflow is considered a driver of inter and intra‐specific life‐history differences among freshwater fish. Therefore, dams and related flow regulation, can have deleterious impacts on their life‐cycles. The main objective of this study is to assess the effects of flow regulation on the growth and reproduction of a non‐migratory fish species. During one year, samples were collected from two populations of Iberian chub, inhabiting rivers with non‐regulated and regulated flow regimes. Flow regulation for water derivation promoted changes in chub’s condition, duration of gonad maturation and spawning, fecundity and oocyte size. However, this non‐migratory species was less responsive to streamflow regulation than a migratory species analysed. Findings from this study are important to understand changes imposed by regulated rivers on fish and can be used as guidelines for flow requirements implementations; RESUMO: O caudal é um dos fatores responsáveis pelo funcionamento dos ciclos de vida das espécies piscícolas dulciaquícolas. As barragens, e a regularização de caudal associada, podem ter impactes nos ciclos de vida destas espécies. O objetivo deste estudo prende‐se com a avaliação dos efeitos da regularização de caudal no crescimento e reprodução de uma espécie piscícola não‐migradora. A análise de amostras recolhidas em populações de escalo do Norte provenientes de dois rios de caudal regularizado e não regularizado, identificaram impactes significativos a nível da condição corporal, da maturação das gónadas e desova, da fecundidade e da dimensão dos oócitos. Esta espécie não‐migradora parece ser menos responsiva à artificialização do caudal que uma espécie migradora previamente analisada. Estes resultados permitem compreender as alterações impostas pela regularização do caudal e podem ser usados em programas de reabilitação fluvial.

Effects of culture conditions on larval growth and survival of stalked barnacles (Pollicipes pollicipes).

Pollicipes pollicipes (Crustacea: Scalpelliformes) is a highly prized food in Portugal and Spain and con- sequently a species of considerable interest to aqua- culture. Surprisingly, however, larval culture conditions for this barnacle have not been opti- mized. This study investigated the effects of temper- ature, diet, photoperiod and salinity on the growth and survival of P. pollicipes larvae. Temperature had a significant effect on specific growth rate (2.6–5.9% total width per day, from 11 to 24°C), reducing mean development time to the cyprid from 25 days at 11 °C to 10 days at 24°C, although this was accompanied by a significant increase in mortality to over 90% above 22°C. Mid- range temperatures (15–20°C) maximized total survival (19–31% respectively). Algal diets of Tetra- selmis suecica, T. suecica/Skeletonema marinoi and S. marinoi/Isochrysis galbana did not affect specific growth rate significantly, but survival (on average 39% in 15 days) and the proportion of high-quality healthy cyprids was significantly higher on the lat- ter two diets (11–15% of initial number of larvae). Photoperiod did not significantly affect the survival, although specific growth rate was significantly higher at 24:0 and 16:8 L:D. Salinity (20– 40 g L 1 range) did not affect growth and survival significantly. The best growth and survival were accomplished using rearing temperatures of 15–20°C, daily feeding with T. suecica/S. marinoi or I. galbana/S. marinoi and a photoperiod of 24:0 L:D.