Dolphinfish Coryphaena Hippurus Research Articles

Interannual variability in dolphinfish Coryphaena hippurus Linnaeus, 1758 growth in the central-southeastern pacific ocean

The present research provides information on Coryphaena hippurus growth variability in the Central-Southeastern Pacific Ocean. For this purpose, fork length of 48 008 specimens obtained from artisanal fisheries (2006–2022) were used to analyze growth by the multi-model inference approach. According to the results, von Bertalanffy model best described species growth based on Akaike’s Information Criterion. Global growth parameters L∞ = 168.6 cm, k = 1.3, t0 = -0.04, indicated fast growth rates of dolphinfish during the study. This model presented growth and longevity values with greater biological coherence than the logistic and Gompertz models. Growth estimates between cohorts indicated that C. hippurus has interannual and decadal variations associated with the El Niño Southern Oscillation (ENSO) and decadal variation. The information in this study is essential for better understanding C. hippurus growth and serves as a basis for future actions on its management and conservation.

Understanding the fishery dynamics and stock health of mahi-mahi Coryphaena hippurus (Linnaeus, 1758) from Indian coastal waters

This work delves into the mahi-mahi (dolphinfish) fishery along the Indian coast, noting itsdevelopmental stage precluding a full assessment. The analysis of population characteristicshighlights their inherent resilience, driven by early maturity, substantial fecundity and rapidgrowth rates. These traits collectively mitigate susceptibility to fishing pressure, ensuringthe maintenance of sizable spawning stock biomasses and recruitment. Through Kobeanalysis, it is determined that the present fishing mortality and biomass levels remain withinsafe thresholds, indicating absence of overfishing. However, regular monitoring is imperativeto swiftly implement management measures if necessary, safeguarding the sustainability ofthe mahi-mahi fishery in the long term. Keywords:Kobe plot, Population characteristics, Recruitment,Resilience, Spawning stock biomass

Morphological characteristics of dolphinfish Coryphaena hippurus Linnaeus 1758 landed in Kalinaun Village, East of Likupang District, North Sulawesi

Morphological characteristics of dolphinfish Coryphaena hippurus Linnaeus 1758 landed in Kalinaun Village, East of Likupang District, North Sulawesi

A multiannual five-fleet generalized depletion model for the stock assessment of the Mediterranean dolphinfish (Coryphaena hippurus) fishery

Abstract Generalized depletion models have proven useful to provide management information for data-limited fisheries. These models are suitable for stocks with fast depletion and recruitment inputs that reset the depletion. The Mediterranean common dolphinfish (Coryphaena hippurus) fishery shows these dynamics, being seasonally exploited mainly by fish aggregation devices in small-scale fisheries from four countries and as bycatch by longline fisheries. These fleets operate on separate fishing grounds, and with distinct effort–catch dynamics. This led to the development of a multiannual five-fleet generalized depletion model applicable to a monthly database of effort, catch, and mean weight from 2008 to 2019. Results showed a high natural mortality rate (0.25 month−1) and wide intra-season fluctuations in biomass. Annual recruitment fluctuates around 10 million individuals, and it has been stable along the analysed period. Exploitation rate only exceeded 40% during the peak month of catches, being much lower the rest of the season, indicating that this stock is fished within sustainable limits. We provide here the first estimation of reference points for the management of the shared dolphinfish Mediterranean stock and show that generalized depletion models can be extended to complex fisheries with multiple fleets with different effort–catch dynamics.

Worms With Armor: Tegumental Adaptations of Stomach Fluke, Dinurussp. (Trematoda: Hemiuridae)—Ultrastructural Characteristics

The stomach is a hostile environment rarely utilized as a habitat by parasites, but stomach flukes are unique helminths that have adapted to survive in this acidic environment. Unlike the flatworms, stomach flukes have a cylindrical body like blood flukes. We hypothesized that, in addition to suckers, stomach flukes are equipped with structures to prevent them from being ripped loose by peristaltic movements and that they have secretory glands to resist the pH of the niche. In the present study, we collected Dinurus sp. (Trematoda: Hemiuridae) from dolphinfish Coryphaena hippurus to understand the tegumental structure and host–parasite interactions. We used ultrastructural and histochemical techniques to investigate the functions of the tegument. The prosoma (proper body) was equipped with densely packed frill‐like tegumental plications with rough and smooth lobes, while the ecsoma (tail) was without plications. Smooth‐lobed prosomal plications had pores (5 μm) that were secretory in function. Secretory granules were delivered from the underlying type‐2 tegumental cells through cytoplasmic connections. Electron‐dense granules coalesced within these cells and were secreted by holocrine method. They were also periodic acid‐Schiff (PAS) and Alcian blue positive. Similarly, PAS positive mucus cells were observed in the gastric pits of the host stomach. Rough‐lobed plications of the flukes enable them to cling onto the mucin. In Dinurus, a glycocalyx forms the outer limit of the tegument. Below the glycocalyx is a stream of cytoplasm devoid of mitochondria, suggesting the tegument is for protection and not for absorption. Under similar conditions, tegumental pores of the ecsoma secreted serine proteinase, which hydrolases gelatin but is incapable of hydrolysis in the presence of serine protease inhibitors. Although additional studies are needed to confirm these initial observations, our study demonstrated for the first time that tegumental plications of stomach fluke Dinurus sp. have mechanical and secretory, not absorptive, functions. Related helminths, blood flukes (schistosomes) are medically important digeneans that cause human diseases. Further, tegumental enzymes in the native form are too scarce for analysis in blood flukes. Unlike blood flukes, Dinurus are relatively large (few mm). Based on the year‐round availability, larger size, and nature of the tegument, we propose Dinurus sp. as an excellent study model for tegumental investigations, such as serine proteinase enzyme analysis.

Climate change alters the temporal persistence of coastal-pelagic fishes off eastern Australia

Abstract The climate-driven redistribution of fisheries species is altering their availability to fishers, necessitating projections of species redistributions that directly relate to future fishing opportunities. We propose that a valuable proxy for fishing opportunity is the proportion of the year that target species are available to fishers, which can be approximated by the temporal persistence of suitable habitat in defined regions. Here, we quantify changes in temporal habitat persistence (months/year) within five eastern Australian bioregions over the period 2010–2060 for four coastal-pelagic fishes: bonito (Sarda australis), spotted mackerel (Scomberomorus munroi), Spanish mackerel (Scomberomorus commerson) and dolphinfish (Coryphaena hippurus). When species were analysed collectively, a significant reduction in the temporal persistence of suitable environmental habitats was evident in the most equatorward (i.e. Tweed-Moreton) bioregion, while significant positive increases were found for poleward bioregions (e.g. Batemans and Twofold Shelf bioregions). The greatest increases in temporal habitat persistence were projected for bonito in the Batemans Shelf bioregion and Spanish mackerel in the Hawkesbury Shelf bioregion (+2.2 and + 1.5 months/year between 10-year averages centered on 2020 and 2050, respectively). By demonstrating temporal habitat persistence as a measure of fishing opportunity, we highlight the potential for this metric to be an effective means of communicating to fishing stakeholders the need to adapt to climate change.

A ten-year monitoring of essential and non-essential elements in the dolphinfish Coryphaena hippurus from the southern Gulf of California

The concentrations of As, Cd, Cu, Pb and Zn were measured in muscle tissue of Coryphaena hippurus captured in the southern Gulf of California to determine inter-annual variations and their relation with environmental parameters for the period 2006–2015; additionally, health risk to consumers was assessed according to levels of studied elements and rate of fish consumption in northwest Mexico. During 2014 and 2015 the levels of As, Cd, Cu, and Zn were significantly lower than the rest of the years; in the case of As, it was also significantly lower in 2010. Oceanic Niño Index was negatively correlated with Zn concentrations in fish, while sea surface temperature was negatively correlated with Zn, Pb and Cd concentrations in dolphinfish. The simultaneous occurrence of the analyzed elements in muscle of dolphinfish indicated that health effects on consumers are not likely to occur; nevertheless, fishermen with elevated fish consumption might be at risk.

The common dolphinfish Coryphaena hippurus linnaeus, 1758 (Perciformes, Coryphaenidae) in the marine waters of Iraq

First record of the common dolphinfish Coryphaena hippurus from the Iraqi marine waters is reported in the present study. One adult specimen (762 mm total length) was caught from the waters surrounding the Khor Abdullah within the Iraqi marine territory. It is a new ichthyofaunal record for the area.

Estimating discard mortality using meta-analysis and fishery-dependent sampling

Estimates of discard mortality are difficult to obtain. Meta-analysis or life-history-based approaches to estimate discard mortality could provide informed estimates when direct empirical estimates are not available. We used data from published literature across a variety of fish species to determine if hooking condition (good vs. poor) and species-specific values for the Brody growth coefficient (K: a measure of fish physiology) were meaningful factors influencing discard mortality in hook and line fisheries. We then examined whether a two-step approach, combining condition- and physiology-specific estimates of discard mortality with data on proportion-by-hooking-condition hooking information for a fishery, could result in an estimate of discard mortality for dolphinfish Coryphaena hippurus comparable to an empirical estimate. A model with hooking condition, K and their interaction best fitted the published discard mortality data. K was an important negative covariate of discard mortality for good hooking condition, with higher K species experiencing greater rates of survival. In contrast, species in poor condition had similarly low rates of survival across a range of K values. Results suggests that hooking condition is the dominant source of mortality when fish are hooked in vital areas but that physiology should also be taken into account when estimating discard mortality for good condition fish. For the recreational dolphinfish fishery in the southeastern US, we estimated a median proportional discard mortality rate of 0.12 (95 % credible set: 0.07, 0.17) when combining the meta-analysis and field-collected proportion-by-condition data. This estimate was lower than the empirical estimate of dolphinfish discard mortality but the credible sets overlapped (median: 0.25; 95 % credible set: 0.05, 0.39). Estimates of discard mortality from our meta-analytic approach may be applicable to fisheries where empirical estimates of discard mortality are not available and hooking injuries are the dominant source of mortality.

Reproductive traits in dolphinfish Coryphaena hippurus Linnaeus, 1758 along the coastal waters of Karnataka, south-eastern Arabian Sea

The maturity, sex ratio, gonadosomatic index (GSI) and fecundity of Coryphaena hippurus was investigated from 347 specimens collected along Karnataka coast, south-eastern Arabian Sea from August 2017 to May 2018. Overall sex ratio of 1:3.5 (male:female) indicated dominance of females in the fishery and differed significantly (p<0.05) in all the months, except in January, May and December. The fork length (FL) at 50% maturity (Lm50) was estimated at 47.5 cm for both males and females. The pattern of GSI and maturity stages suggests peak spawning activity in August-September. However, the incidence of fishes capable spawning all through the year in varied proportions implied that spawning activity occurs throughout the year. The absolute fecundity estimates varied from 1,00,298 eggs for a female of 53.5 cm FL to 6,15,267 eggs for female of 113 cm FL with an average fecundity of 3,18,446 eggs per female. Thefecundity of fish increased with body length and weight as well as with gonad weight. The biological information on maturation, reproductive cycle, spawning periodicity and fecundity of C. hippurus in the tropical Arabian Sea could be useful for developing appropriate management tools and conservation strategies for this commercially important fish species.

Arsenic in the top predators sailfish (Istiophorus platypterus) and dolphinfish (Coryphaena hippurus) off the southeastern Gulf of California.

Distribution of arsenic (As) in tissues and gonads of the Indo-Pacific sailfish Istiophorus platypterus and the dolphinfish Coryphaena hippurus from the SE Gulf of California was evaluated. The bioaccumulation patterns of As were the same in the two species. In I. platypterus, As levels (mg kg-1, wet weight) were gonads (7.4 ± 1.1) > liver (3.1 ± 0.1) > kidney (2.7 ± 0.1) > muscle (1.6 ± 0.1); in C. hippurus, As (mg kg-1) levels were gonads (4.3 ± 0.6) > liver (3.2 ± 0.2) > kidney (2.3 ± 0.1) > muscle (1.2 ± 0.1). Differences in As distribution could be attributed to the biological functions of tissues. The hypothesis was confirmed that biomagnification was evidenced by the fact that As levels were lower in prey species than in predators. Intake of muscle from either fish did not represent a risk to humans if recommended portions a week are not exceeded, adults as much as 1802.4g and 2454.1g and children 257.5 and 350.6g, for sailfish and dolphinfish, respectively. In addition, the likelihood of developing cancer due to consumption of edible tissues from either of these top predators was in the acceptable range (6.4 × 10-5 to 27.3 × 10-6 for a population that consumes 50g of muscle in a week) but if a conservative combined slope factor is used the probabilities to develop bladder and lung cancer increments from 1.1 × 10-3 to 9.1 × 10-5.

Ingestion of macroplastics by common dolphinfish (Coryphaena hippurus) in the Atlantic Ocean

Ingestion of macroplastics by common dolphinfish (Coryphaena hippurus) in the Atlantic Ocean

Water column structure defines vertical habitat of twelve pelagic predators in the South Atlantic

Abstract Quantifying vertical distributions of pelagic predators elucidates pelagic ecosystem structure and informs fisheries management. In the tropical South Atlantic Ocean, the recently designated large-scale marine protected area around Ascension Island hosts diverse pelagic predators for which basin-specific vertical habitat information is minimal or absent. We used pop-up satellite archival tags to analyse vertical habitat use in 12 species (bigeye tuna Thunnus obesus, blue marlin Makaira nigricans, blue shark Prionace glauca, dolphinfish Coryphaena hippurus, Galapagos shark Carcharhinus galapagensis, oceanic whitetip Carcharhinus longimanus, sailfish Istiophorus albicans, silky shark Carcharhinus falciformis, swordfish Xiphias gladius, tiger shark Galeocerdo cuvier, wahoo Acanthocybium solandri, and yellowfin tuna Thunnus albacares) and quantify parameters (temperature, dissolved oxygen, diel cycles, lunar phase) known to constrain vertical movements. Predator depth distributions varied widely, and classification trees grouped predators into four clades: (i) primarily epipelagic; (ii) partial thermocline use; (iii) oscillatory diving with thermocline/sub-thermocline use; and (iv) extensive use of sub-thermocline waters. Vertical habitat differences were linked to thermal physiology and foraging ecology, and species-specific physical constraints from other ocean basins were largely conserved in the South Atlantic. Water column features defined species-specific depth distributions, which can inform fisheries practices and bycatch risk assessments and population estimates.

Predicting bycatch hotspots in tropical tuna purse seine fisheries at the basin scale

Fisheries observer programs represent the most reliable way to collect data on fisheries bycatch. However, their limited coverage leads to important data gaps that preclude bycatch mitigation at the basin scale. Habitat models developed from available fisheries observer programs offer a potential solution to fill these gaps. We focus on tropical tuna purse seine fisheries (TTPSF) that span across the tropics and extensively rely on floating objects (FOBs) for catching tuna schools, leading to the bycatch of other species associated with these objects. Bycatch under floating objects is dominated by five species, including the vulnerable silky shark Carcharhinus falciformis and four bony fishes (oceanic triggerfish Canthidermis maculata, rainbow runner Elagatis bipinnulata, wahoo Acanthocybium solandri, and dolphinfish Coryphaena hippurus). Our objective was to predict possible bycatch hotspots associated with FOBs for these five species across two tropical oceans. We used bycatch data collected from observer programs onboard purse seiners in the Atlantic and Indian oceans. We developed a generalized additive model per species and per ocean relating bycatch to a set of environmental covariates (depth, chlorophyll-a concentration, sea surface temperature, mixed layer depth, surface salinity, total kinetic energy and the density of floating objects) and temporal covariates (year and month). We extrapolated modeled relationships across each ocean within the range of environmental covariates associated with the bycatch data and derived quarterly predictions. We then detected bycatch hotspots as the 90th percentiles of predictions. In the Atlantic Ocean, bycatch hotspots were predicted throughout tropical and subtropical waters with little overlap between species. By contrast in the Indian Ocean, major overlapping hotspots were predicted in the Arabian Sea throughout most of the year for four species, including the silky shark. Our modeling approach provides a new analytical way to fill data gaps in fisheries bycatch. Even with the lack of evaluation inherent to extrapolations, our modeling effort represents the first step to assist bycatch mitigation in TTPSF and is applicable beyond these fisheries.

Two species of Dioncopseudobenedenia Yamaguti, 1965 (Monogenea: Capsalidae) from Naso unicornis (Forsskål) (Acanthuridae) and Coryphaena hippurus Linnaeus (Coryphaenidae) in western Japan, with a description of D. elongata n. sp. from N. unicornis.

Three species of Dioncopseudobenedenia Yamaguti, 1965 (Monogenea: Capsalidae: Benedeniinae) have been described, all found parasitising Naso spp. (Acanthuridae) and Siganus lineatus (Siganidae), in Hawaii, the Great Barrier Reef, and New Caledonia in the Pacific. In this paper, D. elongata n. sp. is described, found parasitising the gills of N. unicornis (Forsskål) caught off Okinawa-jima Island. Dioncopseudobenedenia kala Yamaguti, 1965 is also reported, found parasitising the gills of N. unicornis, and those of a new host, the common dolphinfish Coryphaena hippurus Linnaeus (Coryphaenidae), off Okinawa and Kochi prefectures, Japan. The new species differed from known species in both nuclear (28S rDNA and ITS1-5.8S-ITS2) and mitochondrial DNA (cox1) sequences. Morphologically, the new species differed from other species of Dioncopseudobenedenia in possessing a longer accessory sclerite and a thick, short penis. No species of Dioncopseudobenedenia have been detected during past examinations of C. hippurus; this instance was probably an accidental infection. A key for identification of the species of Dioncopseudobenedenia is also provided herein.

The 2015-2016 El Niño increased infection parameters of copepods on Eastern Tropical Pacific dolphinfish populations.

The oceanographic conditions of the Pacific Ocean are largely modified by El Niño (EN), affecting several ecological processes. Parasites and other marine organisms respond to environmental variation, but the influence of the EN cycle on the seasonal variation of parasitic copepods has not been yet evaluated. We analysed the relation between infection parameters (prevalence and mean intensity) of the widespread parasitic copepods Caligus bonito and Charopinopsis quaternia in the dolphinfish Coryphaena hippurus and oceanography during the strong 2015-16 EN. Fish were collected from capture fisheries on the Ecuadorian coast (Tropical Eastern Pacific) over a 2-year period. Variations of sea surface temperature (SST), salinity, chlorophyll a (Chl-a), Oceanic Niño Index (ONI), total host length (TL) and monthly infection parameters of both copepod species were analysed using time series and cross-correlations. We used the generalised additive models for determine the relationship between environmental variables and infection parameters. The total body length of the ovigerous females and the length of the eggs of C. bonito were measured in both periods. Infection parameters of both C. bonito and Ch. quaternia showed seasonal and annual patterns associated with the variation of environmental variables examined (SST, salinity, Chl-a and ONI 1+2). Infection parameters of both copepod species were significantly correlated with ONI 1+2, SST, TL and Chl-a throughout the GAMLSS model, and the explained deviance contribution ranged from 16%-36%. Our results suggest than an anomaly higher than +0.5°C triggers a risen in infection parameters of both parasitic copepods. This risen could be related to increases in egg length, female numbers and the total length of the ovigerous females in EN period. This study provides the first evidence showing that tropical parasitic copepods are sensitive to the influence of EN event, especially from SST variations. The observed behaviour of parasitic copepods likely affects the host populations and structure of the marine ecosystem at different scales.

Selenium and mercury in dolphinfish (Coryphaena hippurus) from the Gulf of California: inter-annual variations and selenium health benefit value.

With the aim of determining the benefit from consumption of dolphinfish Coryphaena hippurus from La Paz and Cabo San Lucas in the southern area of the Gulf of California, mercury (Hg) and selenium (Se) were measured in liver and muscle of specimens (n = 362) collected between 2006 and 2013. Mean levels of Hg in muscle (0.61 μg g-1) and liver (0.42 μg g-1) of all individuals from La Paz were significantly higher (p < 0.05) than in fish from Cabo San Lucas; in the case of Se, mean concentrations in liver (1.54 μg g-1) of all individuals from La Paz were significantly higher (p < 0.05) than in fish from Cabo San Lucas. Hg levels in muscle were positively and significantly (p < 0.05) correlated with fork length and weight of fish; in liver, Hg and Se were significantly (p < 0.05) correlated with fork length and weight of specimens. Levels of Hg and Se in muscle and liver among years varied significantly (p < 0.05); although there was not a defined pattern of temporal fluctuations for both elements, the lowest Hg levels occurred in 2009 when surface water temperatures were the highest for the sampled years. With respect to the Se health benefit value (HBVSe), results were positive and above the unit in all cases; it implies that consumption of dolphinfish in the southern Gulf of California is beneficial.

Foraging ecology of large pelagic fishes in the US South Atlantic: structured piscivory shapes trophic niche variation

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 631:181-199 (2019) - DOI: https://doi.org/10.3354/meps13126 Foraging ecology of large pelagic fishes in the US South Atlantic: structured piscivory shapes trophic niche variation Stephen J. Poland1,2, Frederick S. Scharf1,*, Michelle D. Staudinger1,3 1Department of Biology and Marine Biology, University of North Carolina Wilmington, 601 S. College Road, Wilmington, NC 28403, USA 2North Carolina Division of Marine Fisheries, 3441 Arendell St., Morehead City, NC 28557, USA 3DOI Northeast Climate Adaptation Science Center, Morrill Science Center, 611 North Pleasant Street, University of Massachusetts, Amherst, MA 01003, USA *Corresponding author: scharff@uncw.edu ABSTRACT: Sustainable management of marine fishery resources requires an understanding of the ecological relationships that contribute to community structure and population dynamics. In offshore marine ecosystems, the functional roles played by many large pelagic predators are poorly understood, yet this knowledge is essential to ecosystem-based management approaches. Here we report on the results of a multiyear (2010-2013) study to evaluate the trophic relationships within a guild of apex predatory fishes in the western Atlantic Ocean. Quantitative diet analyses were completed for wahoo Acanthocybium solandri, dolphinfish Coryphaena hippurus, yellowfin tuna Thunnus albacares, and blackfin tuna T. atlanticus during multiple seasons. Fishes were the most important prey by mass for all predators during all seasons and occurred with high frequency; however, crustacean and molluscan prey were also important dietary components for most of the predators. The diversity of prey eaten was high, with nearly 50 unique families represented; yet, a few prey groups such as scombrid fishes (Auxis spp.), flying fish (exocoetids), and ommastrephid squids, occurred more universally and dominated the diets of some predators during certain seasons. Diet similarity was highest between dolphinfish and blackfin tuna and also between wahoo and yellowfin tuna, but was generally dependent on season and driven by overlap in fish prey. Importantly, the extent of piscivory and specialization on unique fish prey groups supported a structured piscivore guild within this pelagic ecosystem, leading to separation among trophic niches and reduced overlap in prey resources. Our findings provide a temporally (seasonal and inter-annual) extensive evaluation of the trophic relationships among large pelagic fish predators in the US South Atlantic, which should inform an ecosystem-based understanding of community dynamics and fishery impacts. KEY WORDS: Blackfin tuna · Yellowfin tuna · Wahoo · Dolphinfish · Trophic interactions · Predator-prey · Food habits · Trophic niche Full text in pdf format Supplementary material PreviousNextCite this article as: Poland SJ, Scharf FS, Staudinger MD (2019) Foraging ecology of large pelagic fishes in the US South Atlantic: structured piscivory shapes trophic niche variation. Mar Ecol Prog Ser 631:181-199. https://doi.org/10.3354/meps13126 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 631. Online publication date: November 21, 2019 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2019 Inter-Research.

Estimating Discard Mortality for Dolphinfish in a Recreational Hook‐and‐Line Fishery

AbstractMinimum length limits are used to manage Dolphinfish Coryphaena hippurus in the U.S. South Atlantic, but rates of discard mortality are unknown for this fishery and others throughout the species' worldwide range. We estimated discard mortality for Dolphinfish in the U.S. South Atlantic, Caribbean, and Gulf of Mexico recreational hook‐and‐line fishery by using conventional tag–recapture data. Overall, 4,648 Dolphinfish were tagged in these areas between 2002 and 2018 through the efforts of cooperating (fishery‐dependent) taggers as well as research scientists who employed gear types and fishing styles representative of the recreational fishery for this species. The condition of each tagged and released fish was classified as good or poor depending on hook trauma, bleeding, and postrelease swimming behavior. Numbers of tagged and recaptured fish in each release condition were used to estimate condition‐specific discard mortality by fitting a relative risk model. The model assumption of 100% survival of fish in good condition was scaled downward by using numbers of dying fish in good condition from tank holding and satellite tagging experiments. An overall median rate of discard mortality (0.248; 95% credible interval = 0.053–0.389) for the fishery was estimated by summing the products of each condition‐specific mortality rate and the proportion released in each condition. Given relatively high discard mortality rates (&gt;20%), the results suggest that alternative management strategies (e.g., mandatory retention of hook‐traumatized individuals contributing to a bag limit, regardless of size), educating fishers on the use of alternative gear types (e.g., circle hooks), modifying fishing practices (e.g., trolling with heavy drags to reduce rates of deep hooking), or a combination thereof may be more effective solutions than minimum size or bag limits to control the rates of fishing mortality for Dolphinfish.

Spatio-temporal distribution modeling of dolphinfish (Coryphaena hippurus) in the Pacific Ocean off Peru using artisanal longline fishery data

To better understand and characterize the distribution of the dolphinfish Coryphaena hippurus in the Pacific Ocean off Peru, we analyzed spatio-temporal catch per unit effort (CPUE) data from the artisanal longline dolphinfish fishery and oceanographic variables measured from October–March during 2010–2017. A Delta-GAM approach determined that high dolphinfish CPUE occurred during the period from November–January between 9-11°S at an average of 190 nautical miles (nm) from the coast. From February–March, the highest CPUE was located along the coast up to 115 nm offshore between 12-13°S, which suggested that dolphinfish migrate to the southeast during austral summer. However, there was no evidence of a reverse migration towards the northwest, although this result must be corroborated with data taken outside of the dolphinfish fishing season (October–April) in future studies. According to the environmental variables, dolphinfish preferred to stay in waters with sea surface temperatures (SST) that ranged from 22-24 °C, low chlorophyll-a concentrations (CHL; < 1 mg m−3), and surface sea heights (SSH) that ranged from 0.10-0.20 m. The information derived from this study, such as the maps, spatial indicators, and time series, contribute to the knowledge of how the spatial distribution of the dolphinfish and dolphinfish CPUE may vary under future climate conditions and provide some clues that will facilitate fishing ground forecasts in both the short and long term. Finally, our results may provide tools to develop or improve the conservation and management strategies of this species, which supports one of the most important artisanal fisheries in Peru.