The general "nursery habitat" paradigm describes habitats that are distinct to juveniles (because they provide protection from predation, have ample food for lower trophic levels, and suitable environmental conditions). These habitats are used until individuals attain a certain size/age, and then movement to sub-adult/adult habitats occur.
It appears, however, that a single "nursery habitat" definition for a species is appropriate, as species-habitat relationships can change with ontogeny, multiple times even within the first year of life for an estuarine-utilizing fish.
Furey, N.B., Rooker, J.R., 2013. Spatial and temporal shifts in suitable habitat of juvenile southern flounder (Paralichthys lethostigma). Journal of Sea Research 76, 161–169.
What factors about a species life history or its environment mediate or influence how quickly species-habitat changes occur? Would we expect these changes to occur at specific stages, or more across a gradient (gradually)? And if species-habitat relationships are dynamic or even fluid when an organism is a juvenile, how does this impact how we manage habitats? Is this another case of focusing on landscape-based processes rather than habitat-scale? How does this impact the notion of Essential Fish Habitat?
Not sure what you ask about.
To make it simple: adult fish breed in area A. And they will always choose either area A or area similar in conditions. If a juvenile fish was born in area A, it will look for area with similar conditions to breed. Fish like Stizostedion lucioperca or Cottus gobio will try to breed in the area they were born at, but they will search for nearest area with proper conditions. They don't need exactly same area, they need similar conditions. So the changes will occur gradually. Fish A was born in area A and comes back to breed there. But the area has been changed, there are no proper breeding grounds, so fish A travels around and finds area B, breeds there. Next generation of fish will try to breed in area B, if that area is not suitable, they will try to find area C, etc.
Thank you for your thoughts Joanna.
The situation I am referring to, however, is a bit different. For many coastal species, spawning occurs in areas near tidal passes, and juveniles settle in specific estuarine habitats, distinct from adult habitats. Thus, juveniles and adults use different habitat types, presumably for juveniles to avoid predation. Only after much growth does the individual leave juvenile habitats and recruit to the adult population. My question refers to how quickly does the transition occur from juvenile habitats to adult habitats, and what influences the speed and abruptness of this transition.
Hi Nathan,
Presumably, life-history strategy is going to play the biggest role in how fast juveniles leave the nursery areas. If your lifespan is 3 years, then you want to grow up, get out and start breeding asap! For long-lived species, time is not such an issue, so staying safe and taking advantage of a good food supply would be beneficial. There might be a publication or two on lemon shark use of nursery areas in Bimini, Bahamas which could help you out. Seasonality might also play a role in determining nursery area use. If juvenile fish use the weedy edges of ponds to stay safe from predators, but these edges freeze over in winter, then they are forced into deeper water and out of the nursery area. Density-dependence could also play a role. If many juveniles are in a specific nursery habitat, interference competition could limit the usefulness of over-staying.
Essential fish habitat SHOULD account for these factors, but in general, it does not and speaks to the need for buffer zones to mitigate behavioural changes associated with ontogenetic shifts.
Thank you Aleksandra for your input, I think there is a lot of truth in your response. I would imagine not only lifespan, but also growth relative to the structure of the juvenile habitats (if your size prevents the original protective advantages of the juvenile habitat, you will be forced to leave!). Seasonality in the availability of habitat is definitely important and one that is probably overlooked.
I agree in that EFH designations generally don't account for these more subtle ontogenetic shifts, in large part because I think more subtle habitat shifts have not been often looked at (generally, there is a juvenile habitat, and an adult habitat, and that is all). It also certainly makes EFH protection more difficult the more habitat requirements that are defined (and will probably lead to greater areas needing protection), and I like your idea of simply using buffers to facilitate movements to new habitats, but without defining (and protecting) "transitional habitats" (or simply each set of habitats between settlement and recruitment to the adult population) comprehensive habitat protection is unlikely.
Thank you again for your thoughts.
HI, just found your question as I'm new to researchgate. Lots of things affect the timing of habitat shift, but keep in mind that we often are too restrictive of habitat definitions because we do not take account of short-term (diel, tidal) shifts. I have found that permanent shifts can take place in a matter of days and suspect they are often triggered by physiological changes in tolerances to cycles in environmental factors. Ontogenetic shifts can be size related, seasonally forced, or both within a species. For example, environmental factors like temperature form gradients over diel and tidal cycles, but those gradients change seasonally. At some point they can reverse, that is often a trigger for ontogenetic migrations among habitats.
You may be interested in:
Rountree, R.A., and K.W. Able. 1993. Diel variation in decapod crustacean and fish assemblages in New Jersey marsh creeks. Estuarine, Coastal and Shelf Science 37:181-201.
Rountree, R.A., and K.W. Able. 2007. Spatial and temporal habitat use patterns for salt marsh nekton: implications for functions. Aquatic Ecology 41:25-45.
Also my dissertation is available on researchgate
Rountree, R.A. 1992. Fish and macroinvertebrate community structure and habitat use patterns in salt marsh creeks of southern New Jersey, with a discussion of marsh carbon export. Ph.D. Dissertation, Rutgers, The State University of New Jersey. New Brunswick. U.M.I. #DAI-9232951. 292 p.
As well as an unpublished study available on researchgate
Rountree, R.A. and F. Juanes. 2001a. Diel zonation changes in size-specific densities of marsh creek nekton are the rule not the exception.
- Badges
- Science method
- Similar topics
- Biological Science
- Ecology