ML :

There is data/info out there and Dave Willis found it not me and the next PB issue will have info on it from Dave. It is astounding and is worth the subscription price. I will hold off for now but can say it is not the exact study conditions you are asking about.

Every pond is different and it depends on your pond as to recruitment rates . As Dave said in the post linked above BG will choose gravel if they can but it is not required for them to spawn. The question you should ask is why do BG choose gravel if it makes no difference. There is a reason.

I can say this don't buy pea gravel until you read the next PB issue. Cost/ benefit ratios are not something I deal in wrt ponds as every one and its owner are different. I can make that judgment on my ponds but not on others as I don't know their situation pond vs. dollars. I can tell them my experience -- mine is to put one shovel of med. size mixed gravel in the ided BG/RES beds esp. the ones in the center of the colony. I have ,but will not again, spread gravel across the bottom at random. I limit it to proven beds as described above.

I will say this without hesitation -- this forum does not know how lucky it is to have Dave Willis as a member and advisor. If you do any research on fish you will quickly run into a bunch of studies and papers which Dave wrote or took part in on a huge range of fish species and topics. He co-authored the best selling textbook -- Fisheries Techniques 2nd edition and is greatly respected at the top of his professional organization , AFS. There are not many fisheries biologists that in my opinion can match Dave. That is why he is one of a very few who are asked to teach the next generation of fisheries biologists. Dave may have/want/need to be humble about it but I don't have to be. Dave I hope this was not out of line or an embarrassment to you and apologize in advance.