Seeding of luccetti? Maybe you 'and maybe not ..
Continuing with the discussion we will try to touch then, slowly, all other aspects such as placement of juveniles, protection of the areas of care etc..
continue to refer to the example of the pike, I remember, being a fish predator "average" in every sense and 'a good model to talk about this topic.
We assume that there are two classes of factors that influence the size of a population of fish: factors that tend to increase the density 'and those that tend to diminish it.
Can 'seem banal, but this distinction and' the basis for all subsequent management decisions.
In a population in crisis from one side to be blocked as much as' possible causes of decreased density ', while boosting the mechanisms of increased density'.
Come penso chiunque si sia accorto ultimamente le popolazioni di luccio, specialmente in Italia, sono in crisi.
I motivi di questo declino sono senza dubbio molteplici:
- Rimozione da parte dei pescatori
- Mortalita' naturale
- Inquinamento (anche se il luccio per la verita' e' abbastanza resistente)
- Competizione/interazione con altre specie introdotte (luccioperca, bass, siluro) e predazione (p.es. uccelli acquatici)
- Distruzione delle aree di frega e disturbo della stessa
- Malattie e parassitosi
Come detto in tante altre occasioni e' stupido ed inutile agire su di un solo aspetto delle problematiche di un ecosistema. Certamente ha senso dare delle priorita' action phenomena affecting more and those that are solvable with minimal effort, but 'if you do not act a bit' on all fronts is likely to work for nothing.
is to provide for a population of fish in a crisis, think about what you like no matter the species. If this population and 'harassed by all the problems of the previous list try to think of fishing without completely blocking action on other issues.
What would happen?
While not intentionally removing any item from the system would not be able to breed the fish (damn disturbed or missing ranges of care) and the population continues to collapse, there would also periodic die-offs due to pollution and finally you end up with very few examples in a completely degraded.
As the survey also reveals the home page, the opinion is on what is really a priority to address are very different. What is clear, however, 'is that the issues are many and contemporary.
So what to do? let 's see what options are available to increase the stock of a species.
A planting of adult material (photo Esox2000)
introduction of fish
It 's the measure perhaps the most' popular, like the fishermen because '"they throw fish in water" and Like administrators and politicians' cause the money investment is a material response that results in consensus and then vote.
When entries are made of adult fish usually aims to be the so-called "put and take Fisheries", to use Italian terms you enter fishing fish ready to be taken home early by sport fishermen. Generally, these entries are made with sterile individuals, although in some cases, sterilization is not 'total and can' lead to the placing of a new species that involuntary eventually settle.
There are also cases where entries are made of adult fish in affected areas to maximize the survival of fish released (for example, what are friends for Esox2000 ). In
most cases you prefer to enter examples at the end of the larval stage because of lower production costs, while being aware of the disastrous survival rate.
But just how many of these fish survive? How effective are the entries?
It 's very hard to say, or better, and' quite possible to assess the effectiveness of a nuisance but it 's impossible to give a survival rate which is valid for all environments (or for all species).
The main factors which determine the success of such an operation are the density 'of the fry, the availability' food, the density 'of the resident population, the presence and distribution of repair.
In general in the case of the pike you can 'have a survival rate at the end of the first year of between 0.5% and 10%. Fry released in 1000, unfortunately, only 50 will reach an average live next autumn, and even less to reach maturity 'sex, and those' hard to say really .. sure that the goal of a nuisance and 'help the natural reproduction, and because the numbers are sufficiently high (usually in the tens of thousands) in the long run can make a significant contribution. There
'who says that years of alternating density of entries in' years of entries with high low-density 'will simulate the effect of natural reproduction with annual fluctuations but there are no conclusive studies on the subject.
Inoculation of juvenile pike (old photo, launch Low Treviso)
protection and care
'One of the most' popular in the protection of populations during the spawning period is subject to a fishery closures to allow the population to maximize the success of reproduction.
What is rarely applied instead and 'protection of the areas of care themselves. The reeds were removed, the eggs put into dry by the waves of the boats or from changes in water levels. Protecting the natural and
care 'of paramount importance for species such as pike naturally prolific. I remember one mature female produces an average of 25,000 eggs per kg. As we have seen many of those eggs to hatch but do not reach even in a population with a few hundred players, this translates into a significantly high.
protection of the areas and period of care can 'safely allow recovery of a declining population, even without additional measures, if it comes to species with high fecundity'.
Lucci playing in a typical spawning in the Baltic area (photo by Simon Graham, Pike Fly Fishing Articles blog)
Rising immigration from other areas
It 's not the case Pike or at least particularly but not all species perform movements in the waters where they are present. In the case of rivers, the architecture can act as a barrier to these movements effectively isolating stretches of river.
The construction of ladders and allows a natural migration to overcome these barriers. In this way, a declining population may 'increase the mere movement of individuals from an area density' more 'high. Always remember that the movement can 'take place in both directions.
For the pike this could not be so 'as crucial for salmonids but to ensure a flow of individuals between populations helps to distribute the benefits of protected areas, and this applies to all species.
ladder mounts on the River Vantaa in Helsinki (fortunately not all ladders and steps are extreme ..)
For too long it does not return the rest of the points to date to be decided ..
Bibliography:
- Skov et al.
2002 - 1988
Raat - Sutela et al. 2003
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