Small cichlid fry are more likely to be abandoned

[phoenix44]

Another good reason to let parents raise their young.

http://www.practicalfishkeeping.co.uk/c ... ntent=html

It sucks to be runty for some cichlids, according to recent research, which shows that breeding pairs of Striped kribensis (Pelvicachromis taeniatus) are more likely to abandon their young if they are undersized.

Current theory dictates that parents should provide maximum care to broods of high reproductive value (i.e. those that are most likely to survive and reproduce well), whereas parents should reduce care for broods of lower reproductive value to save energy for future reproductive events.

Timo Thünken and co-authors tested this theory by examining the parental investment in relation to offspring quality in the bi-parentally brood-caring Striped kribensis. The results were published in a recent issue of the journal Animal Behaviour

The authors used the size of the offspring as a proxy for quality (larger fish are assumed to be healthier and of a higher quality and reproductive value), and manipulated this by controlling the diet of the free-swimming fry. They then observed parental care for the fry over a period of four weeks.

The authors used 22 pairs of cichlid parents, of which the offspring of 12 pairs were fed well and those of the other 10 pairs were fed poorly. The authors fed the fry with brine shrimp nauplii (which the parents did not eat) and the parents with bloodworms (which the fry did not eat) to eliminate any confounding effects due to the nutritional status of the parents.

The poorly-fed fish were found to be significantly smaller than the well-fed fish at the end of the experimental period. The fish were observed every day for five minutes, during which the observer scored whether the male, the female, both or neither cared for the fry (brood care was defined as one or both parents being one body length or less away from the fry).

The authors also scored the number of times one or both parents ‘jolted’ (a quick twitch of the head and body that signals the fry to settle to the bottom in the presence of danger), as well as the number of times the parents attacked each other.

The authors found parental brood care to decrease with time (this is expected as the fry become less vulnerable to predators with age), and that the parents of poorly-fed fry showed a greater reduction in care than parents of well-fed fry.

According to the authors, this provides the first experimental evidence that the parents adjust their brood-care strategy to brood quality. The results are thus consistent with the parental investment theory suggesting that the optimal level of present investment should maximize the sum of present and future reproductive success.

The authors also found mothers of well-fed fry to show more aggression than their male partners, whereas parents of poorly fed fry did not differ significantly in aggression.

This indicated that the females invested more in brood care, since the increased aggression can be used as an indicator of their defensive behaviour.

This is vindicated by the observation of the authors that the females spent more time protecting the young and gave more warning signals.

For more information, see the paper: Thünken, T, D Meuthen, DCM Bakker and H Kullmann (2010) Parental investment in relation to offspring quality in the biparental cichlid fish Pelvicachromis taeniatus. Animal Behaviour 80, pp. 69–74.

[smidey]

interesting but i don't think that will do our hobby much good if we all left the fry in the tank as the numbers available will be significantly less. in the wild the fish have plenty of space, not 200L to share with all inhabitants so the mortality rate could be higher.

If i use my trophs as an example, there is a group within the group that does the breeding. Keeping trophs, you generally need large numbers to spread the aggression so the runts that may not be very good for breeding later are excellent for keeping the numbers up in the group. horses for courses i guess, they all have their place in the small societies we keep them in.

[ryanjury]

Or another reason to be selective and just cull runts/deformed fish yourself But it is a good article none the same..

[smidey]

Or another reason to be selective and just cull runts/deformed fish yourself But it is a good article none the same..

there is that option to, to me a runt is totally different to a deformed fish. deformed needs to be dealt with but if a runt simply isn'y going to reproduce as well or not at all well that is a natural "un-selection process".

[livingart]

there is some thought in the avian industry that repeated artificial rearing of offspring can affect future generations ability to self rear chicks

[smidey]

even better for MAF's concerns about our fish establishing in the water ways.