The authors assumed that rmax=2 M [61], where M (the natural mortality rate) is estimated from Hoenig’s [62] empirical equation based on observed maximum age. If no maximum age was known, the authors used the von Bertalanffy growth parameter
K and followed Jensen’s Obeticholic Acid manufacturer [63] suggested approximation with M=3/2K. Table 1 generally suggests that very low resilience/productivity (i.e. high vulnerability) is typical of deep-sea fishes, including species that are commonly exploited by deep-sea fisheries. The estimated rmax of the deep-sea species the authors studied has a mean value of less than 0.37 year−1, with high intrinsic vulnerability (i.e., index>60). Similarly, species commonly exploited by deep-sea fisheries have low average rmax of 0.314 year−1. Further, these have markedly lower rmax and higher intrinsic vulnerability index than non-deep-sea fishes (i.e., species generally found shallower than 200 m) of similar length ( Fig. 2). This agrees with results from previous assessments that deep-sea demersal fishes, particularly those that aggregate around seamounts, are more vulnerable than other fishes [24] and [28]. Maximum body size alone may not be a good indicator of resilience or vulnerability to fishing because some of the highly vulnerable species are not large. These metrics of resilience and intrinsic vulnerability, specifically
rmax, can be compared to economic metrics to evaluate IDH inhibitor the sustainability of deep-sea fishing. In species where recruitment is more or less stable at population sizes above 50% of unexploited size, a reasonable assumption for many low-productivity species, the maximum intrinsic growth rate rmax=2M, where M is the natural mortality rate. This
leads to a target fishing mortality rate for maximum sustainable yield (MSY) of Fmsy=M. For species that have maximum ages of 30 years or greater, M is FER expected to be<0.1; thus, maximum fishing mortality rates under standard management models must also be <0.1, a difficult target to meet in open-access fisheries. If a local stock or population is depleted (F⪢Fmsy) and does not receive significant recruitment from unexploited sources, the chances of local extinction are extremely high. Species with restricted geographic range and aggregation behavior are particularly vulnerable to overfishing [46], [55] and [64]. Many deep-sea fishes that inhabit seamounts naturally aggregate for feeding and spawning. These species include orange roughy, splendid alfonsino (Beryx splendens), alfonsino (Beryx decadactylus, Berycidae), blue ling (Molva dypterigia, Lotidae) and slender armourhead (Pseudopentaceros wheeleri, Pentacerotidae). The level of population connectivity among seamounts is unknown for most species but recolonization rates may be very low or episodic [43]. This further reduces their resilience to fishing [24]. With a million dollars capital (=principal) in the bank, one can withdraw $30,000 per year in perpetuity at a guaranteed 3% annual interest rate.