Otolith microstructure and trace elemental concentrations in juvenile Pacific bluefin tuna (Thunnus orientalis) caught off of Southern California in 2012

We combined longitudinal analyses of otolith microstructure and trace elemental composition in ~ age 1-2 Pacific bluefin tuna (PBT, n = 24) for inferring the arrival of individuals in the California Current Large Marine Ecosystem (CCLME). Element:Ca ratios in transverse otolith sections (9-12 rows, triplicate ablations from coreprimordium to edge, ø50 µm) were quantified for eight elements: Li, Mg, Mn, Co, Cu, Zn, Sr, and Ba, which was followed by microstructure analysis to provide age estimates corresponding to each ablation spot. Age estimates from otoliths ranged from 328 to 498 days post hatch. The combined elemental signatures of four elements (Ba, Mg, Co, Cu) showed a significant increase at the otolith edge in approximately half of the individuals (30-60 days prior to catch). Given the different oceanographic properties of oligotrophic open Pacific vs. high nutrient, upwelling CCLME waters, this signal is consistent with the entry of the fish into the CCLME, which was estimated to occur primarily in July after a transoceanic migration of ~1.5-2.0 months.

Effect of ocean acidification on growth and otolith condition of juvenile scup, Stenotomus chrysops

Increasing amounts of atmospheric carbon dioxide (CO2) from human industrial activities are causing changes in global ocean carbonate chemistry, resulting in a reduction in pH, a process termed "ocean acidification." It is important to determine which species are sensitive to elevated levels of CO2 because of potential impacts to ecosystems, marine resources, biodiversity, food webs, populations, and effects on economies. Previous studies with marine fish have documented that exposure to elevated levels of CO2 caused increased growth and larger otoliths in some species. This study was conducted to determine whether the elevated partial pressure of CO2 (pCO2) would have an effect on growth, otolith (ear bone) condition, survival, or the skeleton of juvenile scup, Stenotomus chrysops, a species that supports both important commercial and recreational fisheries. Elevated levels of pCO2 (1200-2600 µatm) had no statistically significant effect on growth, survival, or otolith condition after 8 weeks of rearing. Field data show that in Long Island Sound, where scup spawn, in situ levels of pCO2 are already at levels ranging from 689 to 1828 µatm due to primary productivity, microbial activity, and anthropogenic inputs. These results demonstrate that ocean acidification is not likely to cause adverse effects on the growth and survivability of every species of marine fish. X-ray analysis of the fish revealed a slightly higher incidence of hyperossification in the vertebrae of a few scup from the highest treatments compared to fish from the control treatments. Our results show that juvenile scup are tolerant to increases in seawater pCO2, possibly due to conditions this species encounters in their naturally variable environment and their well-developed pH control mechanisms.

Age and growth parameters of skates of the genus Bathyraja obtained between 2003-2005 along the Argentine continental shelf

In the last 20 years directed shark and ray fishery has increased alarmingly everywhere in the world. For most species though, no data on growth rate, mortality, fecundity and other life history aspects exist as of now and management of the fishery is therefore insufficient. Also there still exist methodological difficulties in the age determination of elasmobranchs fishes, a fact which complicates the investigation of growth parameters. This study tried to identify the best ageing methods and estimate growth parameters for ten skate species of the genus Bathyraja, all occurring in the southwest Atlantic in depths of 50m and more. 720 samples were collected on board of argentine research vessels in between 2003 and 2005. Crystal violet and a new staining method using potassium permanganate, both applied on sagittal sections of vertebral centra, proved to be most effective in enhancing the banding pattern in most of the species. Thorns were also tested and readings were consistent with the ones made on vertebral sections. Growth parameters could be derived for six species and for the other four estimates could be made. Growth rate as well as infinite length varied between species, with those attaining bigger sizes having lower growth rates. No latitudinal differences in growth rate could be detected but a comparison with samples from other studies showed that total lengths were always reported to be higher around the Malvinas Islands.