Can you help me to understand the WE overstocking technique. Would stunting only happen when most of the minnows and smaller YP are gone?
Overstocking WE is a technique where Nate Herman (N8ly - Herman Brothers Pond Management- hbpondmanagement.com ) and I have seen some good results when used in the right habitats with the right fish species present. Although "good results" definately depends on one's goals for the fishery. If you want large WE then this these are not good results. You should contact Herman's for second opinions.
I have only seen this WE overstocking/stunting in a few ponds where YP and 3-4 minnow species are present. The concept is in its infancy. The slow growth of WE in ponds seems to be the standard characteristic of WE in ponds, even if only a few (10-30/ac) per acre are stocked. In ponds of 0.5-2 ac WE seem to rarely get bigger than 5 lbs. Crowding them (50-100/ac) even in larger ponds seems to result in them growing slow and staying small i.e. 19" after 10 yrs. Dr Dave Willis has also reported here and in the PBoss magazine of slow growth of WE where they were crowded. As I recall growth rates increased in the crowded pond after some WE were removed. Maybe he will respond to this thread?
As N8ly and I see it, the benefit of having slow growing small walleye (stunted if you prefer) is they are 'forced' to feed on smaller forage items probably in most cases fish. The smaller the WE is, the smaller its most common forage item will be. IMO if you have YP with WE you want the predator to eat mostly the common smaller YP and not the 8"+ table fare YP. Although what you want is not always what really happens. In my experience, it does not take a real large WE to try and eat an 8" YP. I've caught 8" YP with frayed fins and teeth gashes on the body when 20"-23" WE were present. I not sure how many 7"-8" YP were getting eaten but it was a sign the WE were trying and probably often successfully eating 8" YP. Numerous reports in the scientific literature indicate that adult WE prefer slender forage items of generally smaller sizes. A 16" LMB will eat an 8" YP; saw that happen. The correct forage size is often improtant to maintaining the optimum growth rate for many predators. This is commonly seen with LMB where their growth rate will plateau when their main diet is too small of forage item.
Back to your question. I don't think the stunting of the WE happens only when most of the smaller YP and minnows are gone. My main over WE stocking example is in a 1 ac pond with lots of minnows - GS, fatheads, bluntnose, and spotfins, with some papershell crayfish. Lots of minnows around the entire pond show up at pellet feeding time. YP are present although not abudnant, maybe not even common; many are larger than 8", annual YP spawning occurs. No major weed beds present, rocky, riprap shoreline. I do not know ratios of all the forage species yet. Pond has 100+ WE per acre for going on 11 years. No suplimental WE stocking since 2001. Last fall (2010) 40 more WE (7"-11") were added. Most common WE are 19". From my analysis the WE are feeding on the largest minnows/shiners and smaller YP (2.5"-5") since this size of YP are scarse. I think the WE and many predator fish are eating (selecting) most the largest and most readily available forage item they can eat. Eating too small of forage items for your genetic metabolism is not efficient and leads to slow growth and extra effort for the fish.
WE and YP are bottom oriented fish. YP are primarily day active settling to near bottom at dusk-dark when WE are known to be most active. YP are thus vulnerable to WE predatory habits. Thus the two species are well suited to live together. I think the WE in the example pond are eating a large percentage of the YP due to optimum forage size and availability when WE are 'hunting'. The minnows and shiner are abundant in this example pond due to 1. a non-reproducing predator and not a lot of YOY or young WE are present eating small minnows; lack of recruitment and predator control, 2. minnows and shiners are prolific, annually adding lots soft rayed forage, 3. WE are eating a large percentage of the small YP, 4. YP are relatively scarse resulting low predation pressure on minnows and good growth of YP. 5. WE do not eat a high percentage(?) of small minnows because they are not an efficient food source for 15"-19" WE. 6. Several species of minnows-shiners and papershell crayfish are present thus diversifying the forage base, an important feature in successful fisheries. As small WE are suplimentally stocked then this puts added predation on the minnow forage base and the populations fluctuate accordingly. I am learning that presence of an annual reproducing predator such as LMB does complicate management and fishery balance.
