Instantaneous Mortality Research Articles

Yasunaga et al. (2022) meets the ethics code of Marine Mammal Science, and the journal's decision to publish the paper is correct

Yasunaga et al. (2022) meets the ethics code of <i>Marine Mammal Science</i>, and the journal's decision to publish the paper is correct

Assessment of Stock Status, Metal Contents with Human Health Risk of Gudusia chapra from Oxbow lake, Bangladesh

The current study is focused on a comprehensive stock assessment of Gudusia chapra to assess the stock status along with feeding habits, essential minerals content and risk to human health from exposure to heavy metals. A total of 723 specimens from the Bukvora Baor, Bangladesh were used to estimate the total body length (TL) and body weight (W) which ranged from 5.5 to 14.5 cm and 1.62–26.45 g, respectively. The estimated asymptotic length (L∞) of this species (15.38) was in comparison with average length at 10 cm from 723 specimens along with the rate of 0.70 yr−1 for approaching to asymptotic length. The obtained growth performance index (φ) 2.2 indicates that this species is not economically feasible to bring under aquaculture. At an average annual water surface temperature of 28 °C, natural mortality, 1.71yr−1 indicating good ecological suitability of Bukvora oxbow lake (Baor). The estimated current exploitation ratio (0.24) reflected under-exploitation status with total instantaneous mortality (2.25 years−1) and fishing mortality (0.55 years−1). The recruitment pattern of this species was observed across the year, with main peak occurring during the period of April to May. The estimated total steady state biomass (3.91 metric ton) and MSY (4.40 metric ton) based on length-structured virtual population analysis (VPA) length-structured virtual population analysis (VPA) through FiSAT II schedule indicating the sustainable production of this species. The obtained values of proximate compositions (% of protein, fat, Moisture, ash) showed no significant variations during different seasons throughout the year. The monthly measurements of GaSI showed significant alterations (p < 0.05). The value of essential minerals (Na and Ca) was recorded 9.18 mg and 245.19 mg per 100 g of fish flesh, respectively. Target hazard quotient and Cancer risk for all detected heavy metals were far below the recommended levels by United States Environmental Protection Agency. Therefore, the target fish species from oxbow lake is safe and have no human health risk. Therefore, the outcomes of this research would be very worthwhile in carrying out specific management for G. chapra in Baor ecosystems.

Length-based assessment of an exploited coastal pike (Esox lucius) stock (Rügen, southern Baltic Sea) underscores the crucial relevance of growth and natural mortality for assessment outcomes

Many capture fisheries are considered data-poor, including the northern pike (Esox lucius) fishery in brackish lagoons in the southern Baltic Sea of Germany. The objective of our work was to assess the exploitation status of this stock, which is perceived by stakeholders to be in decline. Size structure data collected via rod-and-reel-angling, fyke nets, and gill nets, and empirical estimates of growth, maturation, and fecundity from the lagoon stock were used to fit the Length-Based Spawning Potential Ratio (LB-SPR) model. Parameter uncertainty in von Bertalanffy growth estimates and natural mortality in the Baltic Sea pike stock was considered in sensitivity analyses. Assessment outcomes were sensitive to estimates of growth rate, particularly asymptotic length L∞, instantaneous natural mortality M, and gear selectivity. Under-aging of old fish in scale-based age estimates overestimated terminal length and generated negative bias in the estimated stock status. Despite the sensitivity of assessment outcomes to life-history parameter choice, the stock status for the Baltic Sea consistently indicated a fully exploited situation with SPRs robustly above 0.4 and current fishing mortality rates between 0.2 and 0.4 yr−1. This result agreed with previous assessments using catch-only models. Our work serves as a reminder, that when using length-based methods, unbiased growth, and natural mortality estimates are critical for robust assessment outcomes.

Plankton size spectra as an indicator of larval success in Pacific sardine (Sardinops sagax)

AbstractEstimating demographic changes in a population requires the measurement of some minimal combination of several vital rates, including the flux of individuals into a population, the population growth rate, individual growth rates and mortality rates. For larval fishes, the ratio of instantaneous mortality to growth (i.e., their ‘recruitment potential’) has been used to make inferences of cohort trajectory where measures of population growth rates are not attainable. Attaining estimates of mortality and growth is an arduous task, and use of the recruitment potential metric has been limited. Here, we relate size spectra of the broader plankton community to the recruitment potential of simultaneously sampled larval Pacific sardines (Sardinops sagax), from three voyages off eastern Australia. As the size structure of a population is determined by the ratio of mortality to growth, and there is remarkable consistency in size spectra across ecosystems, we test the hypothesis that the recruitment potential of larval fish is reflected in community‐level measures of plankton size spectra. Contrary to expectations, results from this study demonstrate a negative relationship between the slope of the plankton size spectra and the recruitment potential of larval Pacific sardine. However, we also demonstrate several other stronger relationships between recruitment potential and physical oceanographic parameters. Together, results suggest plankton size spectra are unlikely to reflect recruitment potential directly. Incorporating some size‐based aspects of the plankton community into a broader modelling framework with a range of oceanographic parameters could further our ability to determine how larval success varies across a seascape.

Stock status of the bogue Boops boops (Walbaum, 1792) in Algerian West Coast (Southwestern Mediterranean Sea)

The current study offered management-related information on the fisheries biology of Boops boops. A subsample of 2068 specimen ranging between 9 to 35 cm total length was obtained from 11 commercial catches on Western Algerian coast. To better understand the growth and mortality, distribution frequency of total length, total length–body weight relationship and age were analyzed for B. boops. The estimated parameters of the Von Bertalanffy growth were L∞=30.045 cm, K = 0.117 year−1 and t0=−2.919 year. The B. boops have a long life span (9 years) with growth performance index estimated at 2.03, and the study area seemed supported mainly by nine age groups. The instantaneous rates of total mortality (Z) was 0.418 year−1, natural mortality (M) was estimated at 0.24 year−1. Rates of fishing mortality (F) and exploitation (E) were 0.178 and 0.43 year−1, respectively. Regarding the fishing effort, the stock of bogue appears overexploited. The yield per recruit (Y’/R = 24.86 g) is very close to the MSY. This result indicates that the bogue’s stock is in a state of full exploitation. The MSY model is more prudent than MSE model in predicting the model.

Informing Management of Atlantic Bluefin Tuna Using Telemetry Data

Sustainable management of exploited marine fish and wildlife populations requires knowledge about their productivity. Survival from natural causes of mortality is a key component of population productivity, but is notoriously difficult to estimate. We evaluate the potential for acoustic telemetry as a long-term monitoring tool to estimate rates of natural mortality. We present a Bayesian multistate mark-recapture model for telemetry data collected over a decade from 188 Atlantic bluefin tuna (Thunnus thynnus) and apply it to estimate the rate of natural mortality using only acoustic tag detections for all animals, or using acoustic tag detections for 96 single-tagged tuna plus acoustic tag detections combined with estimated positions from pop-up satellite archival tags for 92 double-tagged animals. We support the model for bluefin tuna with a simulation study to quantify bias in estimates of population dynamics parameters and investigate the effect of auxiliary information from satellite tagging on mortality rate estimates for different acoustic tag detection probability scenarios.We obtained posterior estimates of the instantaneous annual natural mortality (survival) rate across a decade of tagging for Atlantic bluefin tuna of 0.17 yr-1 (0.84 yr-1) both using only acoustic tagging data, and using a combination of acoustic and satellite tagging data. Use of a prior implying a higher rate of fishing mortality yielded an instantaneous annual natural mortality (survival) estimate of 0.10 yr-1 (0.90 yr-1), with combined acoustic and satellite tag data. Results from the simulation study indicate that the use of satellite tags can improve the precision and accuracy of estimates of detection probabilities, area-specific movement probabilities and mortality rates, where the extent of the improvement depends on true underlying acoustic tag detection probabilities. Our work demonstrates that long-term acoustic tagging data sets have strong potential for monitoring of highly migratory marine fish and wildlife populations, providing information on a number of key parameters, including survival and movement rates. However, improved information on tag reporting rates or fishing mortality is needed to better separate natural and fisheries mortality for Atlantic bluefin tuna.

Reduced lifetime fitness (growth, body condition and survivability) of hatchery-reared tiger pufferfish Takifugu rubripes compared to wild counterparts.

Tiger pufferfish Takifugu rubripes (order Tetraodontiformes, family Tetraodontidae) is a highly exploited species and stocks continue to decline, although hatchery-reared juveniles have been released since 1965 for stock enhancement. To determine why the stock has not recovered through hatchery-release practices, this study investigated and compared the population characteristics of wild and hatchery-origin fish. The length-mass relationship showed that hatchery-origin fish were skinnier, with males weighing less than 90% of the mass of wild males of the same length. The hepatosomatic index tended to be lower in hatchery-origin fish. Age was estimated using the otolith-based method, and the estimates were more accurate and precise than those obtained by the conventional vertebra-based method. At the age of 2.9 years, an age at which specimens were the most abundant in catches, hatchery-origin males weighed only 67% of wild males. The maximum observed age was 12 years for wild fish and 5 years for hatchery-origin fish. The instantaneous total mortality rates of hatchery-origin fish were more than twice as high as those of wild fish. In summary, the hatchery-origin fish had poor health status, poor growth and high mortality, and their fitness in natural environments was therefore hypothesized to be low throughout life.

Population dynamics of the Nile tilapia (Oreochromis niloticus L. 1758) stock in Lake Langeno, Ethiopia

Nile tilapia, Oreochromis niloticus, is a widely distributed and economically most import fish species in Ethiopia. Effective management is essential to sustain their fisheries and the benefits for the local communities. However, little is known about the population dynamics of the Nile tilapia stock in Lake Langeno. Vital parameters of its population were determined using length frequency data collected from 5,949 specimens ranging from 8.5 to 35.7 cm total length (tl). These specimens were collected from August 2017to July 2018. The population parameters were determined using the elefan I routine in FiSAT software. Estimated von Bertalanffy growth parameters were asymptotic length (L∞) = 35.70 cm, growth curvature (K) = 0.32 yr-1, age at length zero (to) = -0.49, and growth performance index (Փ') = 2.61. Instantaneous total mortality (Z), natural mortality (M), and fishing mortality (F) rates were determined from length-converted catch curve and empirical models, respectively, and their values obtained were Z = 2.31 yr-1, M = 0.82 and F =1.56 yr-1, respectively. The exploitation rate (E) of Nile tilapia computed from its mortality rates was 0.67 yr-1, suggesting state of overfishing. The size at first capture (Lc) was estimated at 14.0 cm which is much lower than the size at first maturity (Lm=16.62 cm), which further substantiated the state of overfishing. The results of the study are very useful for fishery managers and scientists who wish to manage and further explore the Nile tilapia stock in Lake Langeno.

Developments in the Quantitative Assessment of Welfare Outcomes in Hunted Mammals Subject to Shooting

Knowledge gaps surrounding animal welfare assessment in hunted terrestrial wild mammals and seals were highlighted in the reviews by Knudsen (2005) and EFSA (2007). Following these reviews, the present paper aims to report on developments in the quantitative assessment of welfare outcomes in wild mammals killed via rifle shooting, and modern explosive harpoon grenades used in the killing of whales. Time to death (TTD) and instantaneous death rate (IDR) are widely accepted ante-mortem variables for assessing the duration of suffering during the killing process. The addition of post-mortem assessments allows for validation of TTD and IDR, thus providing a more accurate appraisal of animal welfare during hunting. While this combined assessment for large cetaceans has been implemented since the 1980s in the Norwegian minke whale (Balaenoptera acutorostrata) hunt, we report that this approach has been implemented in studies of the Icelandic minke and fin whale (Balaenoptera physalus) hunts, as well as the Canadian and Norwegian commercial harp seal (Pagophilus groenlandicus) hunts. Additionally, this approach has been incorporated into welfare studies in terrestrial herbivore management programmes. Quantitative welfare assessment during hunts is capable of effectively evaluating the weapons used and judging modifiable variables such as projectile choice, optimal shooting procedure, as well as identifying areas for improvement in hunter training. In moving towards a standardised approach for welfare outcome assessment, an established framework can effectively allow all hunts to be contrasted and allow for identification of optimal strategies that minimise animal suffering.

Blue catfish population characteristics and dispersal along a Great Plains river gradient

AbstractUnderstanding movement and dispersal dynamics of mobile, large‐river fishes is essential to adopting an ecologically relevant spatial scale for research and management. Movement and dispersal patterns of Blue CatfishIctalurus furcatus, a large‐river specialist, have been mostly investigated in large river systems within their native range, with little emphasis on tributaries and the influence of connectivity. Here, we examine longitudinal movement patterns, natal environments, and population demographics of Blue Catfish in a tributary system of a large Great Plains river. Blue Catfish tagged in the Kansas River were recaptured in five different rivers of varying size and order, and individual movement was highly variable (0–475 rkm). Adult fish (&gt;400 mm) collected within segments (i.e., Segment 1 and 2) of the Kansas River with connectivity to the Missouri River displayed relatively equal natal contributions from the Kansas River (34–48%) and Missouri River (38–65%) while disconnected river segments contained a high percentage (64–87%) of individuals that originated from reservoirs located on tributaries to the Kansas River. The Kansas River segments (Segment 1 and 2) connected with the Missouri River had lower instantaneous mortality (Z = 0.19, SE = 0.05) and higher proportions of large fish (PSD‐M = 9 &amp; 11, PSD‐T = 3 &amp; 5, respectively) compared to disconnected reaches (Z = 0.27, SE = 0.08; PSD‐M = 3, PSD‐T = 0). Mean length of Blue Catfish collected in disconnected reaches were greater than those from connected reaches for individuals at age‐3 and age‐6, and relatively equal at age‐10. Our data provide additional resolution to movement and dispersal patterns of Blue Catfish within large‐river tributary systems, highlight the role of localized reservoir stock contributions, and illustrate species plasticity across varying levels of river network connectivity.

Life-history traits facilitate the population success of the sergeant major Abudefduf saxatilis (Linnaeus, 1758, Perciformes: Pomacentridae) in the Caribbean Sea

ABSTRACT Trade-offs among life-history traits (e.g. growth, reproduction, and survival) are fundamental to the population success of living beings in the wild. This study describes the life-history traits of the sergeant major, Abudefduf saxatilis, one of those fishes most abundant in the coral reefs of the Caribbean Sea. The reproductive biology, age, growth, and abundance of a particular population of A. saxatilis from Mexico was explored using 12 monthly samplings to collect 414 specimens, and abundance monitoring through visual censuses for age-based demographic analysis. Our results indicated that A. saxatilis would have an opportunistic strategy with a type II survivorship curve since the studied population was characterized by fast growth, maturation at intermediate sizes (≈11 cm L T or 2.5 yrs. old), with batch spawning and indeterminate fecundity, protracted spawning season (January to September), high abundance of recruits, low instantaneous natural mortality (M = 0.114 year −1), high life expectancy at birth (e 0 ≈ 4.7 yrs.) and maturity (e α ≈ 2.8 yrs.), and high annual survival of adults and high survival to maturity (). All these life-history traits facilitate the population success of A. saxatilis, showing a high reproductive effort and a rapid population turnover, making this species an efficient colonizer.

High virulence of a naturally occurring entomopathogenic fungal isolate, Metarhizium (Nomuraea) rileyi, against Spodoptera frugiperda

AbstractThe fall armyworm (FAW), Spodoptera frugiperda, is a new and dangerous invasive pest in many countries. Entomopathogenic fungi (EPF) have been considered as potential biological control agents against the FAW. In this study, eight natural fungal strains were isolated from diseased larvae of FAW, and identified as Cladosporium cladosporioides (EFNL‐1), Metarhizium rileyi (EFNL‐2 and EFNL‐8), Fusarium proliferatum (EFNL‐3 and EFNL‐6), F. equiseti (EFNL‐4 and EFNL‐5) and F. tricinctum (EFNL‐7), using the morphological and molecular tools or methods. The instantaneous death risk and mortality of 3rd‐instar larvae inoculated with EFNL‐8 (1 × 108 conidia/ml) were significantly higher than for any other fungal isolates and for the control group. Thereafter, we tested the pathogenicity of EFNL‐8 (1 × 107 conidia/ml) against 1st‐ to 4th‐larvae, pupae, and eggs of FAW. The instantaneous death risk and mortality of 1st‐instar (Median lethal time = 9.02 days; Corrected motality = 88.68%), 2nd‐instar (12.00 days; 62.50%) and 3rd‐instar larvae (13.79 days; 56.67%) inoculated with EFNL‐8 were significantly higher than that of larvae in the control groups. When the eggs of FAW were inoculated with EFNL‐8 (1 × 107 conidia/ml), EFNL‐8 caused eggs (56.62%), and newly hatched neonates after 3 days (68.75%) and 6 days (80.60%) mortality, compared with the control groups. However, the mortality of the EFNL‐8 isolate to 4th‐instar larvae (5.00%) and pupae (14.81%) was low and did not differ from the control groups. This study identified M. rileyi EFNL‐8 as a pathogenic isolate against eggs and 1st‐ to 3rd‐instar larvae of FAW. However, further studies including field validation of this EPF biopesticide candidate should be undertaken in newly invaded areas by the pest.

Use of novel lab assays to examine the effect of pyrethroid-treated bed nets on blood-feeding success and longevity of highly insecticide-resistant Anopheles gambiae s.l. mosquitoes

BackgroundThere is a pressing need to improve understanding of how insecticide resistance affects the functional performance of insecticide-treated nets (ITNs). Standard WHO insecticide resistance monitoring assays are designed for resistance surveillance and do not necessarily provide insight into how different frequencies, mechanisms or intensities of resistance affect the ability of ITNs to reduce malaria transmission.MethodsThe current study presents some novel laboratory-based assays that attempt to better simulate realistic exposure of mosquitoes to ITNs and to quantify impact of exposure not only on instantaneous mortality, but also on blood-feeding and longevity, two traits that are central to transmission. The assays evaluated the performance of a standard ITN (Permanet® 2.0; Vestergaard Frandsen), a ‘next generation’ combination ITN with a resistance-breaking synergist (Permanet® 3.0) and an untreated net (UTN), against field-derived Anopheles gambiae sensu lato mosquitoes from Côte d’Ivoire exhibiting a 1500-fold increase in pyrethroid resistance relative to a standard susceptible strain.ResultsThe study revealed that the standard ITN induced negligible instantaneous mortality against the resistant mosquitoes, whereas the resistance-breaking net caused high mortality and a reduction in blood-feeding. However, both ITNs still impacted long-term survival relative to the UTN. The impact on longevity depended on feeding status, with blood-fed mosquitoes living longer than unfed mosquitoes following ITN exposure. Exposure to both ITNs also reduced the blood-feeding success, the time spent on the net and blood-feeding duration, relative to the untreated net.ConclusionAlthough a standard ITN did not have as substantial instantaneous impact as the resistance-breaking net, it still had significant impacts on traits important for transmission. These results highlight the benefit of improved bioefficacy assays that allow for realistic exposure and consider sub- or pre-lethal effects to help assess the functional significance of insecticide resistance.Graphical

Age, Growth, Mortality and Reproduction Biology of the Black Seabream, Spondyliosoma cantharus in North Aegean Sea, Turkey, Mediterranean Basin

In the present study, the population parameters (length-length and length-weight relationships, age, growth, mortality) and reproductive biology (sex ratio, GSI, condition, length at first maturity, spawning period, fecundity) of black seabream (Spondyliosoma cantharus Linnaeus, 1758) were investigated. The length-length relationship and length-weight relationship were calculated as FL=0.911TL-0.0433 and W=0.0123TL3.0614 (R2=0.97), respectively. Parameters of the von Bertalanffy growth equation were: L∞=33.21 cm, K=0.21 per year, t0= −1.84 year and age varied between 0 and 8 years. The instantaneous rates of total mortality (Z) and natural mortality (M) were 0.64 and 0.47 per year, respectively. Rates for fishing mortality (F) and exploitation (E) were 0.17 and 0.27 per year, respectively. The spawning season extended from February to May and peaked in March and April. The female/male ratio was found to be 3.49/1 and sex inversion from female to male occurred after the 24 cm TL length group. Total lengths at 50% maturity were 22.25 cm for males and 20.59 cm for females. The mean absolute fecundity (F) was 109,457±8,011 oocytes, ranging from 59,666 to 182,589.

Estimating the natural mortality rate of saucer scallops (Ylistrum balloti) on the Queensland east coast from tag-recaptures

Saucer scallops (Ylistrum balloti) were tagged and released on four occasions inside two areas closed to fishing (Hervey Bay A, HBA; and Yeppoon B, YB) on the Queensland (Australia) east coast and their subsequent recaptures over the following months were used to measure the instantaneous rate of natural mortality (M). A total of 13,295 scallops were tagged and 526 recaptured over the 15 month-long experiment (May 2018 to August 2019). Three statistical approaches were applied to the experimental design and analysis of the tagging data, based on 1) the Brownie model, 2) a modified version of the Brownie model, and 3) a binomial logistic regression model of recaptures. Estimates of M based on the Brownie model were much higher for tagged scallops that were at liberty over summer months compared to those at liberty over the winter months, possibly indicating seasonal variation. The logistic model parameter estimates indicated the proportion of recaptures differed significantly with the lunar phase at recapture, scallop size class, the number of days the scallops were at liberty and the interaction between days-at-liberty and closure. All three approaches indicated M was higher in HBA compared to YB. Mean estimates of M for the whole fishery, derived by averaging estimates from both closures, ranged from a minimum of 1.461 year–1 for the logistic model, to 1.501 year–1 for the Brownie model, to 1.548 year–1 (variable recapture rate) and 1.594 year–1 (fixed recapture rate) for the modified Brownie model. Estimates from all three approaches were higher than the previous estimate that was published over 40 years ago and possible reasons for the increase are discussed.

Effects of age composition of Pacific bluefin tuna on their spatiotemporal distribution of active breeding in the south-western North Pacific and on its recruitment strength

Context The south-western North Pacific is one of the main spawning grounds of the Pacific bluefin tuna (Thunnus orientalis) and is targeted by Japanese longline fisheries. Aims This study evaluated the influence of age composition of spawning groups in this area on the strength of recruitment through the spatiotemporal distribution of active breeding. Methods The variation in the recent year-class strength in the area was estimated on the basis of the otolith age estimation and catch data from 2007 to 2016. Key results In the age–frequency distribution, 9 years was the most frequent age class. The instantaneous total mortality after 9 years of age was 0.32. Conclusions On the basis of catch locations and age estimation results, the bias toward young individuals influenced the spatiotemporal pattern of active breeding to shifts to higher latitudes and earlier breeding. In this area, the abundance of the main spawning group (9- and 10-year-old fish) may affect the recruitment of 0-year-old fish, and the older fish are considered to serve as a ‘seed bank’. Implications These results are expected to contribute to the development of appropriate management strategies for spawning stocks in the area and demonstrate the magnitude of the influence of age composition on population fluctuations.

Numerical solution of a Gamma - integral equation using a higher order composite Newton-Cotes formulas

The paper aims at solving a complex equation with Gamma - integral. The solution is the infected size (p) at equilibrium. The approaches are both numerical and analytical methods. As a numerical method, the higher-order composite Newton-Cotes formula is developed and implemented. The results show that the infected size (p) increases along with the shape parameter (k). But the increase has two phases: an increasing rate phase and a decreasing rate phase; both phases can be explained by the instantaneous death rate characteristics of the Gamma distribution hazard function. As an analytical method, the Extreme Value Theory consolidates the numerical solutions of the infected size (p) when k ≥ 1 and provides a solution limit () as k goes to +∞.

An Improved Method for the Estimation and Comparison of Mortality Rates in Fish from Catch‐Curve Data

AbstractCatch‐curve analyses are routinely used to estimate instantaneous mortality (Z) in fish, and as the age‐frequency data are often overdispersed, the application of a variance bias‐correction factor has been recommended. The extensions of the Poisson generalized linear model (GLMPoisson) may, however, constitute a better alternative, as they model the variance (SE) in counts more adequately with their specific dispersion parameter for more accurate estimations and statistical comparisons. To test this idea, simulated age‐frequency data generated under four dispersion scenarios were analyzed according to six currently available methods and compared with the results of a GLMPoissonand five of its extensions to evaluate each method‐specific bias inZ± SE estimates. Empirical age‐frequency data from sampled WalleyeSander vitreusand Arctic CharSalvelinus alpinuspopulations in Québec, Canada, were then used to illustrate the applicability of our GLM‐based method, which relies on the behavior of Pearson residuals to assess model adequacy and an information‐theoretic approach for model selection. All analyses revealed thatZ‐estimates were generally accurate among the methods considered, except under the most likely situation of quadratic overdispersion met in ecological studies, for which only the negative binomial type 2 and the mean‐parametrized Conway–Maxwell–Poisson (CMP) extensions were adequate to estimate bothZand its SE. Linearly overdispersed data were best modeled by the negative binomial type 1 and generalized Poisson (GLMGP) extensions; the GLMCMPand GLMGPwere the most appropriate to model underdispersed data, whereas the GLMPoissonadequately modeled equi‐dispersed data, similar to the Chapman and Robson (1960) method. Statistical comparisons ofZ± SE for grouping factors, such as year or site, were correctly achieved when the most adequate and statistically supported GLMPoissonextension was applied. Altogether, the proposed GLM‐based method should help to circumvent the identified issues related to SE estimation for statistical inferences about mortality rates for fisheries management decision making.

A multi-species assessment of artificial reefs as ecological traps

All of the marine environments have been found to be affected by anthropogenic impacts with the sprawl of marine infrastructure being one of the most extreme factors modifying habitats. Artificial reefs (ARs) are a common type of these infrastructures, that are frequently used for fisheries management, species conservation and habitat restoration. Attractiveness of ARs for some species have been demonstrated, however little is known about the fitness of individuals that occupy ARs compared to natural reefs. ARs that provide lower fitness advantages may become ecological traps. We examined individual fitness of three species (Trachinops caudimaculatus, Vincentia conspersa and Trinorfolkia clarkei) occupying three different habitat types: natural reefs, Reef Ball reefs (RBs) and custom-designed artificial reefs (CDARs) in Port Phillip Bay, Victoria, Australia, through comparing a range of condition indices (hepato-somatic, gonado-somatic and relative weight index). Additionally, we investigated mortality rates of new recruits and juveniles of T. caudimaculatus among habitat types. T. caudimaculatus exhibited nine times higher instantaneous mortality rates on RBs than the other two habitat types. Combined with known habitat preference of T. caudimaculatus for RB, this suggests that RBs may act as an ecological trap for this species. V. conspersa exhibited higher fitness on RBs, while T. clarkei fitness proxies were context dependent. Although our results indicate that responses by fishes to artificial habitats are species-, location- and habitat-specific, this is one of the first studies to demonstrate the formation of ecological traps in the marine environment due to proliferation of artificial reefs.Poorly designed or placed ARs may lead to insufficient positive outcomes or even significant negative impacts on marine communities. Combined with high costs, these effects may lead to reduced social acceptance of new placements and could impede future management and conservation efforts.

Age, growth, and mortality of threatened Warsaw grouper, Hyporthodus nigritus, in the Gulf of Mexico

Warsaw grouper (Hyporthodus nigritus) in the Gulf of Mexico (GoM) are currently managed as a single-stock; however, patchy distribution of suitable habitat may promote the development of discrete populations with different life history characteristics thereby complicating conservation policy. We estimated ages and age-length relationships of Warsaw grouper from different geographic regions in the GoM and applied von Bertalanffy growth functions (VBGF) to estimate growth parameters (L∞ and K) for each region. Otolith-based ages ranged from 1 to 91 years and estimated L∞ and growth coefficient (K) derived from the VBGF for all Warsaw grouper combined were 188.8 cm total length (TL) and 0.034 respectively. Region-specific growth parameters were similar for most of the GoM when VBGFs were limited to Warsaw grouper < 25 years old, though growth was considerably faster from the southeast GoM. When our age-length key was applied to fisheries-dependent length data from the GoM in 2001–2006 and 2011–2016, this fishery was comprised primarily of Warsaw grouper < age-1, but the mean age increased between catches from 2001 to 2006 (4.7 ± 8.3) and 2011–2016 (7.6 ± 6.4). Instantaneous mortality rates (Z) based on the decline of log abundance on age indicated relatively low Z rates across the four regions (range: 0.09−0.18), with a significantly higher mortality rate in the western GoM (0.17) than the eastern GoM (0.08). In this study we also observed a greater longevity (91 years) for the species than previously documented, greater than double the longevity used to develop current management policy.