Pacific halibut chronology of bomb radiocarbon in otoliths from 1944 to 1981 and a validation of ageing methods

Abstract

Pacific halibut Hippoglossus stenolepis of known age were used to create a reference chronology of radiocarbon levels for the years 1944-1981. Levels of radiocarbon in Pacific halibut otoliths pre-1958 were among the lowest reported to date, but radiocarbon levels increased dramatically post-1960. Subsequently, this reference chronology was used to validate ages determined using the standard break and burn and surface ageing technique. These older fish were collected at a later date but were born during this period of rapidly increasing radiocarbon levels. Otolith cores were compared to the reference chronology based upon the presumed birth year determined from annulus counts and year of capture. The ages derived from both break and burn and surface ageing methods were determined to be accurate. # 2004 The Fisheries Society of the British Isles

Age validation of canary rockfish (Sebastes pinniger) using two independent otolith techniques: lead-radium and bomb radiocarbon dating

“…Because yelloweye rockfish were relatively easy to age from growth zone counts (CV = 4%) and lead-radium dating provided support for the age estimation procedures, a series of yelloweye rockfish otoliths were used to establish a bomb radiocarbon chronometer for the northeastern Pacific Ocean (Kerr et al 2004). The chronometer established by Kerr et al (2004) was further corroborated by an independent study of juvenile Pacific halibut (Hippoglossus stenolepis) from a similar region (Piner and Wischniowski 2004). These records subsequently provided an independent chronometer for age validation of the quillback (S. maliger; Kerr et al 2005) and bocaccio (S. paucispinis; Andrews et al 2005) rockfishes.…”

“…1940 to 1956 from the range of estimated birth years), the biggest assumption is some degree of regional specificity for the ontogeny of each fish sampled. For the Pacific halibut samples, five samples were from young of the year fish that experienced a pelagic phase of up to six to seven months and six samples were 3 to 5 yr fish (cored to the first year) that would have experienced the pelagic phase and possibly a migration period (Piner and Wischniowski 2004). Rockfishes are known to have a pelagic larval stage as well, but the potential complication for using these data as regional indicators of 14 C is potential movement over great distances as an adult.…”

“…For example, a minimum lifespan of 30 to 38 years was determined for the red snapper (Lutjanus campechanus) based on these principles (Baker and Wilson 2001). In addition, age can also be determined by projecting measured 14 C levels back to a reference time series (Campana 1997, Andrews et al 2005 or a series of samples with different collection years and ages can be selected to validate age estimation procedures for a range of age classes younger than the minimum lifespan (Piner and Wischniowski 2004).…”

Age validation of the North Atlantic stock of wreckfish (Polyprion americanus), based on bomb radiocarbon (14C), and new estimates of life history parameters

“…Researchers also have also documented a similar phase shift in bomb radiocarbon levels in the Pacific Ocean. A radiocarbon validation study performed on canary rockfish (Sebastes pinniger) revealed that differences in oceanographic conditions caused by upwelling caused a phase shift of 5-6 years between the radiocarbon chronologies of canary rockfish and that of a reference chronology developed from Pacific halibut (Hippoglossus stenolepis) (Piner et al, 2004).…”

“…Without a realistic estimate of M, fishing-induced mortality cannot be estimated from the age or size composition of commercial catches, and the effects of fishing mortality on future yields cannot be predicted. Methods used to estimate M treat it either as a constant value (Pauly, 1980;Hoenig, 1983;Alagajara, 1984;Polovina and Ralston, 1987;Hewitt and Hoenig, 2005;Then et al, 2015) or as an age-or size-varying parameter (Lorenzen, 1996;Gislason et al, 2010;Charnov et al, 2013), but the latter is the generally preferred method for estimating M.…”