نتایج جستجو برای: natural and fishing mortality

تعداد نتایج: 16915710  

2002
R. E. Grift A. D. Rijnsdorp S. Barot M. Heino U. Dieckmann

We analyse the potential of intensive exploitation to have caused evolutionary changes in the age and length at maturation in North Sea plaice Pleuronectes platessa. Such evolutionary change in the onset of maturation is expected given that fishing mortality is more than four times higher than natural mortality. In order to disentangle phenotypic plasticity from evolutionary change, we employ t...

2003
A. L. Jensen

Jensen, A.L., 1991. Simulation of fish population responses to exploitation. Ecol. Modelling, 55: 203-218. A model that couples Larkin's predator-prey model, Ivlev's feeding model, Ursin's growth equation and the exponential mortality model was applied for simulation of the responses of fish populations to exploitation. Simulations were done without food-limited growth, with food-limited growth...

پایان نامه :وزارت علوم، تحقیقات و فناوری - دانشگاه پیام نور - دانشگاه پیام نور استان تهران - دانشکده زیست شناسی 1388

126 abstract: in this research we studied the effects of cyclic hydration and dehydration of cysts of artemia urmiana and artemia parthenogenetica on the hatching percentage, survival and growth. the experiment was carried out in 3 treatments (1-3 hydration/dehydration cycles) with 3 replicates for each treatment. later effects of cold preservation at -20°c during three time periods were ...

2014
Graham M. Pilling Shelton J. Harley Nick Davies Joel Rice

We assess the potential consequences of recent (2012) fishing conditions on the future biological status of the three tropical tuna stocks, based upon the new tropical tuna stock assessments. Projected status in 2032 is reported relative to spawning biomass and fishing mortality reference points in absolute terms (as a median of the projection outcomes) and in probabilistic terms. Here, we have...

2015
Fabian Zimmermann Christian Jørgensen

Fishing reduces stock size and shifts demographics, and selective mortality may also lead to evolutionary changes. Previous studies suggest that traits may change evolutionarily because of fishing on decadal time scales. Here we examine the potential bioeconomic impacts of fishing-induced evolutionary change. We used a life-history model with stock dynamics based on evolving maturation age, whi...

2014
Magnus Huss André M. de Roos Anieke Van Leeuwen Anna Gårdmark M. Huss

Predators commonly share prey with human exploiters, intuitively suggesting that there is an inherent human–predator conflict through competition for prey. Here we studied the effects of fishing and predation mortality on biomass distributions and yields of shared prey using a size-structured model of competing populations, describing the life histories of Baltic Sea sprat and herring. Whereas ...

2002
Mika Rahikainen Sakari Kuikka Raimo Parmanne

A plea for linking assessment and management to the broader ecosystem state has been made several times in the fisheries literature. The need for ecosystem considerations is obvious for Baltic herring stock which has experienced large fluctuations in growth and natural mortality rate. Biological reference points, based on stock-recruitment data, have gained importance under precautionary approa...

پایان نامه :وزارت علوم، تحقیقات و فناوری - دانشگاه علامه طباطبایی 1389

after the soviet union dissolution, a chaotic period was begun in the russia. russia lost its glory and felt disgrace. the first group of elites came to power under yeltsin; they tried to re-define russia’s identity as a european country and build a foreign policy on this baseline. therefore russia tried to become closer with the west especially with the u.s. according to their view the sovie...

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