Fish Population Dynamics - Science topic

Sorry for not be able tot help you. N ow, I am a retired reseracher, and my field was related with abalone and lobster fisheries.

I use other models, but never VPA.

I would recommend not thinking of t₀ as the age at zero length (theoretical or otherwise) but simply as a convenient adjustment that allows the von Bertalanffy function to better fit age/length data from rather older individuals. Fish are not obliged to grow according to the von B function. It is only a useful approximation to their biology and it is one that does not fit well to the growth patterns of the very young -- hence the need for a t₀ parameter. If, however, t₀ is only a convenient adjustment, then it has no meaning outside of a particular fit of the von B function to a particular dataset and there is no point in trying to calculate a value for it, other than as a side product of fitting the equation.

Think of some indicators (independent variables) like swt, pH, salinity, DO etc and dependent variable like CI of fish (species-wise), distribution, community structure and have a correlation study

Unfortunately, due to a combination of weather and increasingly difficult waters to sample (and of course a pandemic that stopped travel at a crucial time to the Lake District) I still have some waters to sample to get a complete picture (mainly some of the remaining lakes in the valleys). As I'm no longer an active researcher (after running a music agency I'm now running a distillery) this is taking longer than originally planned. But I will get there! It occurs to me too that DNAe would work on some waters if/when enough sequences are available from the fin clippings. I envy you being able to go "fishing" in the Amazon basin. Well done!

Hi Alessandro

Similar mix of species to what we have in the Mexican Pacific... We tagged a few M. tarapacana in Brazil and we are writing a paper about that. For those (up to 3 m DW) I see no issue with the 31 mm darts. But for the 1.5 m animals and smaller I would go with the 20 mm darts.

Good luck

Ramón

Thanks Bradly!

It is not directly linked to grotwh but there are several studies on hermaphroditic fish species that relate gonads infected by parasites with an earlier timing of sex change (likely affecting overall fitness): 

Whenever I've modeled fish movements it usually involves a probability matrix, a matrix containing the probabilities of moving from one habitat to the next, etc. Often times the probability of staying in a habitat is just 1-p(moving). I'm not familiar with Fishmove package, but the probability of not moving is likely a derived quantity from the probability of moving.

Hope this helps.

JP

Fixation in buffered formalin may have a small effect on gonad weight, however it shouldn't be large as the fixative is intended to avoid significant distortion of tissues. I have provided a link to a study done on spanish mackerel, which are superficially similar to sablefish, and provides conversion equations which may be useful.  

This paper may help you. 

best wishes and regards 

Sandeep K P

Try use Cormack-Jolly-Seber model to estimate population parameters

Thanks, Glen, I was one of the authors on that Delta Smelt paper, hence my interest in the topic.

One example would be the Konijnendijk et al. (2011) study of Lake Victoria cichlids in International Journal of Evolutionary Biology (http://dx.doi.org/10.4061/2011/616320).  An early community genetics analysis, published by Wares (2002) in Molecular Ecology, also included teleosts (DOI: 10.1046/j.1365-294X.2002.01510.x)

Thanks Dan Gwinn, certainly the paper by Maunder and Punt is also quite useful and is probably the follow up of the initial report I was referring to (below). In any case, the message is the same, it may be possible to use CPUEs of different nature to compare trends in abundance or insert them in stock assessment models if properly standardized. Also, Mark Maunder has produced several papers that are quite useful to address the question under discussion here and many are freely available in the web.

Nikoline, there are hundreds (maybe thousands) of papers on your topic. It has been one of the most important issues addressed by fisheries science over several decades. What there may not be is one paper that neatly summarizes all of that work. Indeed, I rather doubt that there is even one textbook that could be relied upon to draw together all of the ideas and information.

I should add a warning: Many scientists who have studied the topic have too readily assumed that a relationship between the size of the spawning population and recruitment is driven only by the amount of egg production influencing the numbers of future recruits, forgetting that the number of recruits influences the future size of the spawning population (and so egg production). Disentangling those two can be difficult when analyzing a data set. It can be impossible when examining a paper written by someone who did not themselves check for the direction (or directions) of cause and effect.

So ... a very large literature on a very complex topic, some of the papers being problematic. 

This question is not clear. If you mean the zone of an existing fishery, then you will need a set of fishing data from the fishery. If you want to determine the fishing zone of a new fishery, then you may have to conduct a survey to determene the zone

The first article discusses r/k-selection in great detail. Generally, resources availability, population density and environmental stability all influence the evolution of life history, and variation in such parameters has been shown to induce changes in life history traits.

The second article puts this in context with range shifts, which often result in the change of many ecological factors and thence different optimal strategies.

I hope this is of any help.

Why is ANOVA not appropriate to your question? If you explain why ANOVA is not a viable choice it will be clearer what needs you have. As Emmanuel says it is important to understand the context much more in order to advise on appropriate statistical tests.

One simple approach is to use a non-linear model with an extra term for temperature (or whatever). I was coauthor on a study where we did this, see eq. 2:

Also test for autocorrelation in the residuals. We used the nlme package in R.

I agree with Aleksandra. If you want to be sure on the source of origin you have to do this with DNA analysis. Nevertheless, there is possibly more than one source and very likely also several events (many?) when this shrimp arrived in Japan. Ballast water is in many cases of introduction the likely source but I suggest to check ballast water tanks directly. This can be a problem if there are no regulations by law. Otherwise you are dependent on the good will. If you do not check the ballast water, you will always stay with 'the likely source is ...'. Besides ballast water also the fouling matrix on ship hulls is capable to transport invertebrates and even small fish. Drift is dependent on currents and I do not know the currents in this region.

Mukund,

The following link is a paper I wrote about estimating fish populations in rivers with mark-recapture. We present some methods that can help simplify methods and prevent the need for more complex open-population models. Good luck!

Dan

I suggest you use pudes bio economy approach to work the issue AQUACULTURE eg hypotemus have the case where you plecostomus climatological variables include the DEA approach