Stable ocean hypothesis
The stable ocean hypothesis (SOH) is one of several hypotheses within larval fish ecology that attempt to explain recruitment variability (Figure 1; Table 1). The SOH is the notion that favorable and somewhat stable physical and biological ocean conditions, such as the flow of currents and food availability, are important to the survival of young fish larvae and their future recruitment. In the presence of stable ocean conditions, concentrations of prey form in stratified ocean layers; more specifically, stable ocean conditions refer to “calm periods in upwelling ecosystems (sometimes called 'Lasker events')” that cause the water column to become vertically stratified. The concept is that these strata concentrate both fish larvae and plankton, which results an increase of the fish larvae feeding because of the density-dependent increase in predator-prey interactions. Lasker is attributed with constructing this hypothesis in the late 1970s by building on previous larval fish research and conducting his own experiments. He based the SOH on case studies of clupeid population fluctuations and larval experimentation.
| Author | Year | Name | Summary | Comments |
| Hjort | 1914 | Critical period hypothesis | Larval survival pivots on whether or not a larval fish successfully feeds during the “critical period” when it transitions from relying on its yolk sac to exogenous food sources | Myopic view of larval starvation being the primary factor in larval recruitment variability |
| Cites marine fisheries of northern Europe | ||||
| 1926 | Aberrant drift hypothesis | Larval recruitment is affected by winds and ocean currents which cause dispersal of eggs and larvae, removing them from essential larval and juvenile habitat | Provided the foundation for future larval recruitment paradigms, but was under-tested until recently, when both starvation and oceanographic movements have been recognized as important factors | |
| Also cites marine food fisheries of northern Europe, like cod | ||||
| Cushing | 1974; 1990 | Match-mismatch hypothesis | Success of larval recruitment is linked to a temporal alignment of fish reproducing, larvae hatching, and plankton (prey) blooming (generally associated with spring) | An evolved hypothesis combining both of Hjort's founding concepts |
| Cites Atlantic cod | ||||
| Lasker | 1978 | Stable ocean hypothesis | When tranquil ocean conditions occur in upwelling systems, the water column becomes stratified in layers that concentrate larvae and plankton, which increases successful larval feeding, which increases larval recruitment and contributes to year class strength | Relevant to larval survival, but does not correlate strongly to variations in recruitment (Peterman and Bradford 1987) |
| Cites northern anchovies in the Pacific | ||||
| Cury and Roy et al. | 1989; 1992 | Optimal environmental window | In upwelling systems, wind, storm, and other energetic events cause turbulence that, within an optimal range, increase larval recruitment; dependent upon the presence/absences of Ekman transport | Builds upon Lasker's Stable Ocean hypothesis |
| Hypothesis | Cites Peruvian anchoveta, Pacific sardines, and West African sardines | |||
| Iles and Sinclair | 1982 | Stable retention hypothesis | Prey availability is not as critical to recruitment as the physical retention of the larvae, so spawning events must coincide with suitable wind and current conditions | Adaptation of and forward progress on Hjort's aberrant drift hypothesis |
| Cites Atlantic herring | ||||
| Sale | 1978; 1991 | Lottery hypothesis | Variability in tropical fish recruitment is dependent on pre- and post-settlement dynamics | Contrasts Hjort's original perspectives |
| Supported by modern research (Doherty, 2002; Cowen 2002) | ||||
| Cites tropical reef fish |