TheGill‐Oxygen Limitation Theoryand size at maturity/maximum size relationships for salmonid populations occupying flowing waters

Abstract

The slowing of growth as fish age has long been believed to be related to energy expenditure for maturation, and this rationalization has been used to explain why, across nearly all fish species, the relationship between size at first maturity (Lm) and maximum (Lmax) or asymptotic length (L∞) is relatively constant. In contrast, the Gill‐Oxygen Limitation Theory (GOLT) postulates that (a) fish growth slows because as they grow, their two‐dimensional ability to extract oxygen from the water diminishes relative to their three‐dimensional weight gain, and (b) they can only invest energy for maturation if oxygen supply at their size at first maturity (Qm) exceeds that needed for maintenance metabolism (Q∞). It has been reported previously across dozens of marine fish species that the relationship between Qm and Q∞ is linear and, further, it can be mathematically converted to Lm vs. L∞ by raising both terms to the power of D (the gill surface factor), resulting in a slope of 1.36. If the GOLT is universal, a similar slope should exist for LmD vs. L∞D relationships for freshwater species across multiple individual populations that reside in disparate habitats, although to our knowledge this has never been evaluated. For analysis, we used existing data from previous studies conducted on 51 stream‐dwelling populations of redband trout Oncorhynchus mykiss gairdneri, Yellowstone cutthroat trout O. clarkii bouvieri and mountain whitefish Prosopium williamsoni. The resulting LmD vs. L∞D slopes combining all data points (1.35) or for all species considered separately (range = 1.29–1.40) were indeed equivalent to the slope originally produced for the marine species from which the GOLT‐derived relationship was first reported. We briefly discuss select papers both supporting and resisting various aspects of the GOLT, note that it could potentially explain shrinking sizes of marine fish, and call for more concerted research efforts combining laboratory and field expertise in fish growth research.

The Sizes, Growth and Reproduction of Arrow Worms (Chaetognatha) in Light of the Gill-Oxygen Limitation Theory (GOLT)

“…Figure 6, based on Table 5, shows that in chaetognaths, L max , when plotted vs. L m in a regression with zero intercept, leads to a slope of 1.30, which is close to the estimate of 1.35 for teleosts [35,36], and well within its 95% confidence interval of 1.22-1.53 (see Pauly [16]). This suggests that maturity, in chaetognaths, is triggered by the oxygen supply to their tissues dropping, as they grow and their surface area/volume ratio declines, to a level near 1.3 times their maintenance metabolism, as also occurs in fish [16,35].…”

“…In fishes, mean length at first maturity (L m , i.e., the length at which 50% of the individuals are mature) occurs at [16,35,36]. Here, we also tested whether chaetognaths reach maturity and spawn at a fraction of their maximum length (L max ) that is similar to that of fishes.…”

Growth and status of Nile tilapia (Oreochromis niloticus L.) stock in Lake Chamo, Ethiopia

“…Another important factor facilitating the excellent growth performance of O. niloticus in Lake Chamo is the optimum dissolved oxygen (DO) concentration in the lake (Table 5). There is abundant theoretical and empirical support in the literature for oxygen being both a limiting and controlling factor for the growth of fish and aquatic invertebrates (Amarasinghe & Pauly, 2021;Diaz Pauli et al, 2017;Kolding et al, 2008;Meyer & Schill, 2021;Pauly, 1981Pauly, , 2019Pauly, , 2021Peck & Chapelle, 2003;Pörtner & Peck, 2010;. The gill-oxygen limitation theory (GOLT) proposed by Pauly (1981) provides mechanisms for key biological aspects, including food conversion efficiency, growth and the timing of fish maturation.…”

“…According to the GOLT principle, the surface area of the gills cannot, as a two-dimensional structure, supply fish with sufficient oxygen to keep up with the growth of their three-dimensional bodies (Pauly, 2021). Thus, a lower relative oxygen supply induces sexual maturation and a subsequent slowing and cessation of growth (Amarasinghe & Pauly, 2021;Meyer & Schill, 2021;Pauly, 2021). Moreover, the desirable DO level for Nile tilapia farming in culture conditions ranges between 3.0 and 8.0 mg/L (Hussain, 2004).…”

The gill-oxygen limitation theory (GOLT) and its critics

“…Thus, when the growth of teleosts causes their metabolic rate to drop to about 1.3 to 1.4 times their maintenance metabolic rate (i.e., something that fish can monitor in real time), then sexual maturation is initiated. Figure 4 (D to F) provides further examples of this generalization [see also (101)].…”