Yellowfin Tuna Thunnus Albacares Research Articles

Age validation of yellowfin tuna Thunnus albacares in the Indian Ocean using post-peak bomb radiocarbon chronologies

Yellowfin tuna Thunnus albacares stock assessments use age-structured models; therefore, accurate methods for ageing the catch are required. Age estimation techniques need to be validated at the population level to ensure accuracy. However, otolith-based age estimates of yellowfin tuna have never been validated in the Indian Ocean. The current study provides the first age validation for Indian Ocean yellowfin tuna using the post-peak decline period of the bomb radiocarbon (14C) chronometer. A 14C reference chronology based on accelerator mass spectrometry assays of known-age yellowfin tuna otoliths was consistent with published regional coral records, with all showing similar rates of decline during the 2000 to 2019 study period. After back-calculating the birth years of sub-adult and adult yellowfin tuna from otolith increment counts, Δ14C values measured in the early growth portion of the otolith were compared with the observed decline slope of the reference chronology. There were no significant differences between the birth years of validation and reference samples, supporting the otolith increment age determination methodology between the ages of 2.2 and 10.5 yr. The validation of age and growth estimates is expected to benefit assessment models for Indian Ocean yellowfin tuna. We recommend that otoliths from large fish continue to be collected to expand the validation to older fish. Greater precision in the validation results will also require a larger reference chronology.

Highly active fish in low oxygen environments: vertical movements and behavioural responses of bigeye and yellowfin tunas to oxygen minimum zones in the eastern Pacific Ocean

Oxygen minimum zones in the open ocean are predicted to significantly increase in volume over the coming decades as a result of anthropogenic climatic warming. The resulting reduction in dissolved oxygen (DO) in the pelagic realm is likely to have detrimental impacts on water-breathing organisms, particularly those with higher metabolic rates, such as billfish, tunas, and sharks. However, little is known about how free-living fish respond to low DO environments, and therefore, the effect increasing OMZs will have cannot be predicted reliably. Here, we compare the responses of two active predators (bigeye tuna Thunnus obesus and yellowfin tuna Thunnus albacares) to DO at depth throughout the eastern Pacific Ocean. Using time-series data from 267 tagged tunas (59,910 days) and 3D maps of modelled DO, we find that yellowfin tuna respond to low DO at depth by spending more time in shallower, more oxygenated waters. By contrast, bigeye tuna, which forage at deeper depths well below the thermocline, show fewer changes in their use of the water column. However, we find that bigeye tuna increased the frequency of brief upward vertical excursions they performed by four times when DO at depth was lower, but with no concomitant significant difference in temperature, suggesting that this behaviour is driven in part by the need to re-oxygenate following time spent in hypoxic waters. These findings suggest that increasing OMZs will impact the behaviour of these commercially important species, and it is therefore likely that other water-breathing predators with higher metabolic rates will face similar pressures. A more comprehensive understanding of the effect of shoaling OMZs on pelagic fish vertical habitat use, which may increase their vulnerability to surface fisheries, will be important to obtain if these effects are to be mitigated by future management actions.

Movement and vertical habitat use of yellowfin tuna Thunnus albacares in a vertically compressed habitat: the Galápagos Marine Reserve.

Tropical pelagic predators are exploited by fisheries and their movements are influenced by factors including prey availability, temperature, and dissolved oxygen levels. As the biophysical parameters vary greatly within the range of circumtropical species, local studies are needed to define those species' habitat preference and model possible behavioral responses under different climate change scenarios. Here, we tagged yellowfin tuna Thunnus albacares in the Galápagos Marine Reserve and tracked the horizontal and vertical movements of eight individuals for 4-97 days. The tuna traveled a mean of 13.6 km day-1 horizontally and dispersed throughout the archipelago and in offshore waters inside the Galápagos Marine Reserve and in the surrounding Ecuadorian exclusive economic zone. Vertically, they traveled a mean of 2 km day-1 , although high-resolution data from a recovered tag suggested that transmitted data underestimated their vertical movement by a factor of 5.5. The tracked yellowfin tuna spent most of their time near the surface, with an overall mean swimming depth of 24.3 ± 46.6 m, and stayed shallower at night (11.1 ± 16.3 m) than during the day ( 37.7 ± 60.9 m), but on occasion dived to cold, oxygen-poor waters below 200 m. Deep dives were commonly made during the day with a mean recovery period of 51 min between exposures to modeled oxygen-limiting conditions <1.5 mL L-1 , presumably to re-oxygenate. The depth and frequency of dives were likely limited by dissolved oxygen levels, as oxygen-depleted conditions reach shallow depths in this region. The main habitat of tracked yellowfin tunas was in the shallow mixed layer, which may leave them vulnerable to fishing. Vertical expansion of low-oxygen waters under future climate change scenarios may further compress their habitat, increasing their vulnerability to surface fishing gear.

Species associated with whale sharks Rhincodontypus (Orectolobiformes, Rhincodontidae) in the Galapagos Archipelago.

Whale sharks Rhincodontypus frequently appear to interact or associate with other species, which vary depending on the community structure and the demographic of the whale sharks at each location globally. Here, we present the species sighted frequently around whale sharks in the Galapagos Archipelago and reported by dive guides and scientists and also in earlier publications. These associated species include cetacean species: bottlenose dolphins Tursiopstruncatus, other shark species: silky sharks Carcharhinusfalciformis, Galapagos sharks Carcharhinusgalapagensis, scalloped hammerhead sharks Sphyrnalewini, tiger sharks Galeocerdocuvier and teleost fish species: remoras Remora remora, yellowfin tuna Thunnusalbacares, almaco jacks Seriolarivoliana and black jacks Caranxlugubris. The recording of interspecies associations and interactions may lead to better understanding of the natural history of whale sharks and can show important symbiotic relationships or interdependence between different species.

Impact of Salinity Changes on the Antioxidation of Juvenile Yellowfin Tuna (Thunnus albacares)

To understand the impacts of salinity stress on the antioxidation of yellowfin tuna Thunnus albacares, 72 fishes (646.52 ± 66.32 g) were randomly divided into two treatments (32‰ and 29‰) and sampled at four time points (0 h, 12 h, 24 h, and 48 h). The salinity of the control group (32‰) was based on natural filtered seawater and the salinity of the stress group (29‰) was reduced by adding tap water with 24 h aeration to the natural filtered seawater. The superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and malondialdehyde (MDA) from liver, gill, and muscle tissues were used as the antioxidant indexes in this study. The results showed that the changes of SOD and GSH-Px in the gills were first not significantly different from the control group (p &gt; 0.05) and finally significantly higher than the control group (SOD: 50.57%, GSH-Px: 195.95%, p &lt; 0.05). SOD activity in fish liver was not significantly changed from 0 h to 48 h (p &gt; 0.05), and was not significantly different between the stress group and control group (p &gt; 0.05). With the increase in stress time, GSH-Px and MDA activities in the liver of juvenile yellowfin tuna increased first (GSH-Px: 113.42%, MDA: 137.45%) and then reduced (GSH-Px: −62.37%, MDA: −16.90%) to levels similar to the control group. The SOD activity in the white and red muscle of juvenile yellowfin tuna first decreased (white muscle: −27.51%, red muscle: −15.52%) and then increased (white muscle: 7.30%, red muscle: 3.70%) to the level of the control group. The activities of GSH-Px and MDA in white and red muscle increased first (white muscle GSH-Px: 81.96%, red muscle GSH-Px: 233.08%, white muscle MDA: 26.89%, red muscle MDA: 64.68%) and then decreased (white muscle GSH-Px: −48.03%, red muscle GSH-Px: −28.94%, white muscle MDA: −15.93%, red muscle MDA: −28.67%) to the level observed in the control group. The results from the present study indicate that low salinity may lead to changes in the antioxidant function of yellowfin tuna juveniles. In contrast, yellowfin tuna juveniles have strong adaptability to the salinity of 29‰. However, excessive stress may consume the body’s reserves and reduce the body’s resistance.

Connectivity in juvenile yellowfin tuna Thunnus albacares between temperate and tropical regions of the western Pacific Ocean

Yellowfin tuna Thunnus albacares is a commercially important fish species widely distributed between 40° S and 40° N. Mixing rates between tropical and temperate areas of the western Pacific Ocean were investigated using stable carbon (δ13Cotolith) and oxygen isotopes (δ18Ootolith) in whole otoliths of small juveniles (mean: 5.8 cm standard length, SL) and in otolith cores of large juveniles (32.4 cm SL). The density distribution of δ18Ootolith values for small juveniles showed a significant difference between the areas, whereas patterns for large juveniles were almost identical between areas. In addition, modal values for large juveniles spanned several small juvenile modes. The density distribution of δ13Cotolith values for small juveniles had a single significantly different mode for each area, whereas the distribution of δ13Cotolith values for large juveniles in these areas was bimodal, particularly in the temperate area; these modes corresponded to those for small juveniles in each area. These modal patterns indicate that the majority of large juveniles captured in the temperate area have tropical origins, and mixing from tropical to temperate areas occurs between the areas before recruitment to fisheries in each area. These connectivity patterns during early life history can contribute to refinement of stock assessments of this commercially valuable species.

No evidence from long-term analysis of yellowfin tuna condition that drifting fish aggregating devices act as ecological traps

Human-induced habitat modifications can severely impact the biology and behavior of wild species. Drifting fish aggregating devices (DFADs), used by industrial purse-seine tropical tuna fisheries, significantly increased the number of floating objects found in the open ocean, with which tropical tuna associate. This habitat change has raised concerns over the risk of modifying the behavior and altering the biology of tuna and other associated species (the so-called ecological trap hypothesis). Relying on a time-series from 1987-2019 of more than 25000 length-weight samples collected in the western Indian Ocean, we reject the hypothesis that the body condition (Le Cren’s relative condition factor, Kn) of yellowfin tuna Thunnus albacares decreased concurrently with the increased number of DFADs. This result suggests the absence of negative long-term impacts of DFADs on the condition of tuna. As other factors may have counteracted possible negative effects of DFADs, we recommend long-term monitoring of the habitat along with biological and behavioral parameters of tunas to detect any critical change.

Relative abundance of yellowfin tuna Thunnus albacares (Bonnaterre, 1788) in the tropical area of the north-eastern Indian Ocean

The tropical area of the north-eastern Indian Ocean has historically been a prominent fishing ground for yellowfin tunaThunnus albacares (Bonnaterre, 1788). However, low effort from either Japanese or Taiwanese fleet in the last two decadeshas driven some uncertainties in relative abundance estimates of yellowfin tuna, which affects the robustness of the currentstock analysis for an already declined population. Hence this study was carried out to bridge the research gap by utilising theIndonesian scientific observer data from 2006-2021, which covers the north-eastern Indian Ocean. A delta-lognormal modelwas adopted to fit the data, with the catch per unit effort as the response variable and year, quarter, moon phase, latitudeand longitude as known covariates. The optimal model was chosen using a backward method based on Akaike InformationCriterion (AIC) (Akaike, 1974), Bayesian Information Criterion (BIC) (Schwarz, 1978) and the values of the coefficientof determination (R2). In general, the relative abundance of yellowfin tuna remained at a very low level, with an apparentdeclining trend in the first decade, followed by a slight sign of recovery in the past three years. However, the increasing trendwas overshadowed by uncertainties, likely caused due to natural variation and low coverage in some years. Although theseries was considered short, it managed to picture the dynamics of the abundance of yellowfin tuna in the tropical area of thenorth-eastern Indian Ocean, which is essential for conducting a more robust harvest strategy evaluation. Keywords: Declining stock, Fisheries-independent data, Highly migratory, Relative abundance, Scientific observer

Temporal and Spatial Relationships of Yellowfin Tuna to Deepwater Petroleum Platforms in the Northern Gulf of Mexico

AbstractIn 2006–2007, 110 Yellowfin Tuna Thunnus albacares were tagged with acoustic transmitters near deepwater oil platforms and one drillship in the northern Gulf of Mexico off the Mississippi River delta to determine the extent to which platforms act as fish aggregating devices (FADs). Vemco acoustic receivers were installed on six deepwater platforms to detect the presence of tagged individuals. Five of 12 Yellowfin Tuna captured in 2006 were detected in 2007, demonstrating multi‐year presence in the region. Ninety Yellowfin Tuna were detected in 2007, resulting in 221 platform residencies and 32 single detections. Duration of residence at a platform was positively correlated with the platform's depth, and the number of transitions decreased with platform‐to‐platform distance. In total, 109 movements between platforms by 46 (51%) different individuals were detected, traveling distances of up to 98.2 km. Yellowfin Tuna displayed interactions with deepwater platforms in the northern Gulf of Mexico similar to their interactions with FADs and other studied geological features, by way of aggregating or using them as meeting points, landmarks, and stopovers within a movement corridor. The large number of oil and gas platforms located in the northern Gulf of Mexico may have a significant effect on distribution, retention, and migration of Yellowfin Tuna populations in this area of the gulf.

Determination of Geographical and Seasonal Variations of Heavy Metals in Swordfish (Xiphias gladius) and Yellowfin Tuna (Thunnus albacares)

Bioaccumulation of heavy metals in marine fish is a major concern worldwide and it leads to some economical burdens for the tropical fish exporters. However, data is yet to be unavailable in Sri Lanka in this regard. Hence this study was conducted to explore geographical variation of heavy metal accumulation in the Swordfish (Xiphias gladius) and Yellowfin tuna (Thunnus albacares) as they play a predominant role in the export fish market in Sri Lanka. Secondary heavy metal analysis data of Mercury, Led, Arsenic and Cadmium were collected from two major fish export companies in Sri Lanka during the period of 2015 to 2017. Particular points were traced with the aid of log sheets and heavy metal variations were mapped against fish species and heavy metal concentrations by using QGIS software. Heavy metal analysis data were concentrated between 64 to 70 longitudes and 0 to 8 latitudes, 76 to 80 longitudes and 0 to 8 latitudes, 88 to 92 longitudes and 14 to18 latitudes and 82 to 90 longitudes and 6 to 14 latitudes. Heavy metals such as Cd, As and Pb were not detected in the fish samples. Mercury was the major heavy metal accumulated among the tested and high concentration was detected in Swordfish. Mercury accumulation was highest in longitudes between 64 to 70 and latitudes of 0 to 8.This shows serious health issues that are challenging to humans and provides clear evidence on marine pollution. It is recommended to prevent fishing in these particular areas. Proactive measures and techniques need to be applied to fix safe limits of heavy metals in these natural aquatic ecosystems and protect the organisms in the environment.

Reproductive Biology of Yellowfin Tuna (Thunnus albacares) in Tropical Western and Central Pacific Ocean

A total of 756 yellowfin tuna (Thunnus albacares) caught by a Chinese drifting longliner in the tropical western and central Pacific Ocean (WCPO) from May 2018 to March 2019 were investigated to describe the reproductive biology of the species. Generalized linear model and polytomous logistic regression for the ordinal response model were employed to assess the effects of biometric and spatiotemporal factors (such as individual fork length (FL), fishing depth, dissolved oxygen, and month) on the reproductive traits of yellowfin tuna. The results showed that FLs ranged from 87 to 163 cm, averaging 115.8 cm (SD = ±14.2) for females and 121.8 cm (SD = ±16.8) for males. The proportion of males in the sampled fish was 0.61 (SD = ±0.29), and larger males (&gt;130 cm) were proportionally predominant. Analyses based on the monthly variation of the gonadosomatic index and monthly proportion of sexual maturity stages of the gonads showed that the main spawning period of yellowfin tuna lasts from September to December. In addition, the 50% first maturity FLs of males and females were 111.96 cm (SD = ±1.04) and 119.64 cm (SD = ±1.30), respectively. This study provides new information on the reproductive development of T. albacares in the tropical WCPO region. These reproductive parameters reduce uncertainty in current stock assessment models, which will ultimately assist the fishery in becoming sustainable for future generations.

Can Stomach Content and Microbiomes of Tuna Provide Near Real-Time Detection of Ecosystem Composition in the Pacific Ocean?

This preliminary study used DNA metabarcoding to test whether the stomach content and gut microbiome of tuna could be a viable near real-time monitoring tool for detecting composition and change in oceanic ecosystems. The gut content of skipjack (Katsuwonus pelamis, n=55) and yellowfin tuna (Thunnus albacares, n=46) captured in the Pacific Ocean during El Niño Southern Oscillation events (ENSO) between 2015-2017 were examined by high throughput sequencing and complemented by morphological assessments to identify fishes, crustaceans and cephalopods in the stomach content. Gut microbiome was examined solely by high throughput sequencing. Stomach content and gut microbiome were compared between tuna species, ENSO events and capture location using generalised linear models. The full model (tuna species, capture location and interaction with ENSO) best explained fish prey composition, while capture location and ENSO weakly explained the composition of crustaceans and cephalopods. Skipjack and yellowfin tuna captured near coastal areas (Longitude&amp;lt;170°W) showed a greater diversity of prey compared to fish captured in oceanic regions of the Pacific, while Thunnus albacares showed a much more diverse stomach content than K. pelamis (21 fish, eight cephalopods and six crustaceans). Fish captured during La Niña events showed higher prey diversity compared to fish captured during El Niño. Tuna species best explained differences in gut microbiome to the Phylum level, while no model explained gut microbiome differences to the Order or Family level. This preliminary study shows that capture location and ENSO events explained differences in stomach content of K. pelamis and T. albacares, while tuna species best explained gut microbiome assemblages to the Phylum level.

Interannual Variability of Yellowfin Tuna (Thunnus albacares) and Bigeye Tuna (Thunnus obesus) Catches in the Southwestern Tropical Indian Ocean and Its Relationship to Climate Variability

This study investigated the interannual variability of yellowfin tuna (Thunnus albacares) and bigeye tuna (Thunnus obesus) catches in the southwestern tropical Indian Ocean (SWTIO) over 25 years and its relationship to climate variability. The results indicate that the catch amount in the northern SWTIO exhibits a significant relationship with the temperature, salinity, and current variability in the upper ocean (&amp;lt; 400 m), associated with a significant subsurface upwelling variability, which is prominent only in the northern region. An increase of the tuna catches in the northern region is associated with the deepening of the thermocline depth and 20°C isotherm depth of the Seychelles–Chagos Thermocline Ridge, indicating suppression of the subsurface upwelling. Further analysis reveals that the catch amounts in the SWTIO tend to increase during the positive phase of the Indian Ocean Dipole. However, the catch variability in the northern SWTIO is more closely related to the El Niño–Southern Oscillation than the Indian Ocean Dipole. Favorable conditions for catches seem to develop in the northern region during El Niño years and continue throughout the following years. This relationship suggests the potential predictability of catch amounts in the northern SWTIO, an energetic region with strong subsurface upwelling variability.

Inactivation kinetics of different flexible packing materials for decontamination of yellowfin tuna Thunnus albacares using pulsed light technology

Comparative efficiency of three different packing materials for post-packaging decontamination of yellowfin tuna Thunnus albacares steaks using pulsed light (PL) technology was investigated during the study. The packing materials used were 300 gauge low density polyethylene (LDPE), 12 µ polyester 300 guage polyethylene (PEST/PE) and 300 gauge cast polypropylene (CPP). Inactivation curves were plotted separately for each material for pulsed light exposure time ranging from 0 to 12 s. The curves were fitted with three different models viz, (i) log-linear, (ii) log-linear with Geeraerd and (iii) log-linear with Weibull model and corresponding goodness-of-fit statistics were estimated. Considering the least treatment time for achieving log microbial reduction, CPP was found to be the ideal choice among the three packaging materials. Among the three models, considering the lowest root-mean-square error values (0.0291, 0.0210 and 0.0141 for samples packed in LDPE, PEST/PE and CPP respectively), Weibull model was found to be most appropriate for describing the inactivation curves in all sample cases. Therefore, inactivation curves of steaks packed in CPP was validated with the Weibull model. The corresponding root-mean-square error (0.1036) and correlation coefficient (0.9974) showed that this model can be effectively utilised for modelling the microbial inactivation kinetics using pulsed light technology.Keywords: Cast polypropylene, Inactivation kinetics, Non-thermal processing, Pulsed light technology, Statistical modelling, Yellowfin tuna

Overcoming Catch Data Collection Challenges and Traceability Implementation Barriers in a Sustainable, Small-Scale Fishery

The seafood sector faces both socioeconomic and environmental sustainability challenges, as well as pressure to demonstrate progress from governments, NGOs, retailers, and consumers. To document data elements necessary in verifying key sustainability attributes and fishery progress, the sector needs to implement traceability systems accessible to fishers and other vulnerable near-shore actors. Implementation must overcome a suite of technological, social, and economic barriers. We assessed and reviewed the efficacy of several approaches attempted in a Philippines yellowfin tuna (Thunnus albacares) fishery. The current prevailing approach is a centralized, analog method of catch recording, both broadly across the Philippines and specifically in this MSC-certified fishery, where they have implemented enumerator-facilitated catch certificate recording. The fishery has begun developing, testing, and piloting new decentralized digital models, including NFC cards, RFID tags, and an app-based smartphone catch data capture. All approaches encountered barriers to uptake, and the most recent estimates suggest up to 44% of the catch in the Philippines remains unreported. We discuss additional systemic considerations necessary to advance sustainability outcomes and their documentation through traceability systems in the seafood sector originating with small-scale fishers.

Application of Surplus Production Model to the Yellowfin Tuna Thunnus albacares in the northern and western parts of Aceh waters

Yellowfin tuna Thunnus albacares is one of pelagic fish that has high potential and economic value in Banda Aceh. Utilization of this resource in Banda Aceh is using purse seine units, with the number of purse seines continuously increasing. Therefore, management needs to be done so that optimal productivity can be maintained. This study discusses the estimation of catch and effort at maximum sustainable yield (MSY) of yellowfin tuna based on catch per unit effort (CPUE) and purse seine production in Banda Aceh during 2013-2018. Mathematical analysis was carried out using the equilibrium approach with the Schaefer model. The highest catch of yellowfin tuna reached 191 tons (July) and the average CPUE for yellowfin tuna was 0.796 tons/trip with CMSY of 2,482 tons/year and EMSY of 2,765 trips/year. From 2015 to 2018, the trend of biomass continued to decline and overfishing occurred during this period.

Analysis of sizes and state of ovarian maturity in yellowfin tuna (Thunnus albacares) captured in the Gulf of Mexico

The yellowfin tuna Thunnus albacares is the second most important fishery in Mexico, due to its production costs and commercial value” The species is fished on both coast of the country, with the Pacific Ocean presenting productions lightly higher than that of the Gulf of Mexico where, in spite of the above statement, tuna catches have recently shown a downward trend. For this reason, analysis is required of the size and stage of ovarian maturity and it is necessary to determine whether capture size is the primary reason behind the decline in the yellowfin tuna fishery Three tuna fishing trips were conducted in the Gulf of Mexico in order to gather data pertaining to fork length (Lf) and gonads Histological sections were obtained from the latter for analysis and determination of maturity stage. The results showed that males were predominant (40%) among the individuals for which the sex could be differentiated in the catches of T. albacares. The Lf values in the catch, were between 75 and 162 cm. However, variations in this parameter were found between sexes. The relationship between length and weight showed that the males are larger than the females, however, the equationgiven by the parameters of a=0.9406 and b= 3.4504, demonstrated growth of positive allometric type in both sexes. There was progressive development in the state of ovarian maturity over the months of capture. Chromatin nuclear (CN) was the most frequent phase within primary ovarian development (November, February, March), stages were present, although these did not present a direct relationship to fork length.

Onset of nutrient consumption during early life stage digestive system development of two tuna species (Thunnus orientalis and Thunnus albacares)

To specify the timing of exogenous nutrient consumption in the larvae of two commercially important tuna species, the Pacific bluefin tuna (PBF) Thunnus orientalis and the yellowfin tuna (YFT) Thunnus albacares, the gene expressions of peptide transporter 1 (PEPT1) were examined. The mRNA expressions of PEPT1 first occurred at 2 days post hatching (dph) in PBF larvae and 3 dph for the YFT, and PEPT1 was found to only be expressed in the intestinal tract. The histological changes of the digestive tract of the YFT larvae were observed and compared to PBF larvae from a previous study. The intestines were developed at the hatching day for both species. It was found that the developmental timing of internal organs differed between the species, with the YFT showing an approximately one-day delay. The major organs such as liver, pancreas and gall bladder that excrete digestive enzymes appeared at 1 dph for PBF and 2 dph for YFT. The development of external morphological features was similar to organ development timings, with mouth-opening and first feeding starting at 2 dph for PBF, and 3 dph for YFT. Growth during the first month is rapid and variable for both species, ranging from 1.06 to 1.56 mm/d. Our findings provide new information about the early onset of feeding and larval development for the two species which would contribute to future aquaculture.

Age and Growth of Yellowfin Tuna in the U.S. Gulf of Mexico and Western Atlantic

AbstractAge, growth, and mortality were estimated for Yellowfin Tuna Thunnus albacares from the U.S. Gulf of Mexico and western Atlantic Ocean. During 2004–2017, 3,443 Yellowfin Tuna were sampled, primarily from recreational landings off the coast of Louisiana (90%). Based on reading otoliths, ages ranged from 1 to 18 years, with younger fish (&lt;4 years) representing the majority (78%) of the age‐classes. Otolith weight was allometrically related to fish age (r2 = 0.91), which suggests that it may be a useful tool in indirectly estimating age given the challenges associated with directly aging tropical tunas. Based on Akaike’s information criterion (AIC), the Richards growth model had the most parsimonious fit to the length‐at‐age data (average maximum length L∞ = 1,658 mm, growth coefficient k = 0.23 year−1, a = 1.04, b = 0.45) compared to the von Bertalanffy growth model (L∞ = 1,589 mm, k = 0.36 year−1, theoretical age at zero length t0 = −0.8 year; AIC difference = 26.21), which had a relatively poor fit. The size‐modified Richards model, which assumed a truncated error structure at the minimum size limit (686 mm curved fork length [CFL]) in fishery‐dependent collections, improved the fit in the smallest individuals and was therefore the preferred model. Males and females had similar maximum ages (18 and 17 years, respectively) but showed significant differences in growth, with males reaching a larger L∞ than females (size‐modified Richards: 1,706 versus 1,568 mm CFL, respectively). Baseline natural mortality (M) using a maximum age of 18 years was 0.346 and was then scaled across age‐classes. These growth and mortality estimates and the individual age data have been used in improving stock assessments for Yellowfin Tuna to support scientific management.

Monitoring of the status of eleven bony and cartilaginous fish populations in the Malpelo Sanctuary of Fauna and Flora, Colombian Pacific

To determine trends over time in the relative abundance of species prioritized in the Malpelo Fauna and Flroa Sanctuary Management Plan, underwater visual censuses were done from April 2009 to August 2019. Data were collected for five species of bonefish: bluefin trevally (Caranx melampygus), longfin yellowtail (Seriola rivoliana), yellowfin tuna (Thunnus albacares), leather bass (Dermatolepis dermatolepis) and sailfin grouper (Mycteroperca olfax), and six cartilaginous fish: spotted eagle ray (Aetobatus laticeps), silky shark (Carcharhinus falciformis), Galapagos shark (Carcharhinus galapagensis), whitetip reef shark (Triaenodon obesus), whale shark (Rhincodon typus) and scalloped hammerhead shark (Sphyrna lewini). A negative non-significant trend in abundance through time was observed for most of the evaluated species, except A. laticeps and T. obesus, which showed positive non-significant trends. The hammerhead shark (S. lewini) was the only species that showed a statistically significant decrease in abundance over time. The results of this study highlight the urgent need to establish more effective fisheries management and regulation measures that promote the conservation of important fish species, not just inside the sanctuary but also within the Tropical Eastern Pacific.