21 research outputs found
The egg production and spawning stock size of the North Sea mackerel and horse mackerel stocks in 1988
During the period 5 April to 28 July 1988 the spawning areas of North Sea
mackerel and horse mackerel were investigated by research vessels from the
Netherlands, Denmark and Norway. Based on the plankton samples and
temperature observations obtained during this period the egg production
and spawning stock size were estimated. The total egg production of
mackerel represents a spawning stock biomass of 37 000
tonnes, which is about 20 % less than the 1986 estimate. The total egg
production of horse mackerel represents a spawning stock
size of 110 000 tonnes
The egg production and spawning stock size of the North Sea mackerel stock in 1990
During the period 12 March to 20 July 1990 the spawning area of the North
Sea mackerel was investigated by research vessels from the Netherlands,
Denmark and Norway. Based on the plankton samples and temperature
observations obtained during this period the egg production and spawning
stock size were estimated. The estimated total egg production of mackerel
(53 x 10^12 eggs) represents a spawning stock biomass of 78 000 tonnes,
which is about twice the estimate in 1988
The egg production and spawning stock size of the North Sea mackerel stock in 1984
During the period 22 May to 17 July the spawning area of North Sea
mackerel was investigated by research vessels from Scotland, the
Netherlands, Denmark and Norway. Based on the 629 plankton samples and
temperature observations obtained during this period the egg production
and spawning stock size were estimated
Aggressive Incidents in Residential Youth Care
It is assumed that group climate can have an effect on aggressive behavior in adolescents living in residential facilities, but it is largely unknown whether there are climate differences between the various types of residential institutions, and whether group climate differently affects aggression incidents among adolescents placed in institutions that differ in levels of security (and openness). In current research, the differences in perception of group climate between open, semi-secure, and secure residential youth care facilities were examined as well as the association between group climate and aggression. In total, 159 adolescents (96 males, 63 females) completed the Prison Group Climate Instrument (PGCI), and (aggressive) incidents were recorded during a period of 3 months. Perception of group climate-including support from staff, group atmosphere among adolescents, possibilities for growth, and repression-did not differ between the various types of residential care, except for possibilities for growth. Adolescents in open and semi-secure institutions experienced more possibilities for growth than their peers in secure institutions. A more positive perception of group climate in open institutions proved to be related to less aggressive incidents at the living group. For semi-secure and secure institutions, no relation between group climate and aggression was found. Also, the longer adolescents stayed in residential youth care, the more aggressive incidents occurred