The 2026 result fits a pattern that survey scientists have observed across more than five decades of monitoring. Years of below-average recruitment, meaning the survival of young fish into the juvenile stage, have historically been followed by years of average to above-average production. The weak year classes of 1999, 2002, 2012 and 2024 were each succeeded by stronger showings in 2000, 2003, 2013 and now 2025 and 2026. Jack Buchanan, a marine scientist at VIMS and chief scientist of the seine survey, noted that while this year’s class is considered average in terms of abundance, it represents a significant increase from 2024. He emphasized that striped bass recruitment can swing considerably from year to year, and that a single year of poor production can be partially offset by the output of the previous or following year, a dynamic that helps stabilize the overall population and the fisheries it supports.

The survey’s methodology is deliberately simple and rigorously standardized, which is what allows comparisons across 59 years of data. Scientists sample 18 index sites distributed across the Rappahannock, York and James River systems, the three major Virginia tributaries where striped bass spawn. Each site is visited five times between mid-June and early September, and on every visit researchers deploy a 100-foot seine net from the shore, drawing it through the shallow water where juvenile striped bass congregate. Captured fish are counted, measured and returned alive to the river. At this time of year, young striped bass typically measure between 1.5 and 4 inches long. In 2026, the team measured 2,648 juvenile striped bass at the Virginia index sites, a sample size large enough to characterize the year class with statistical confidence.

The Virginia survey has been run annually since 1967, when the state’s fisheries managers first recognized the need for a consistent index of spawning success. It is conducted for the Virginia Marine Resources Commission and feeds directly into coastwide stock assessments for striped bass managed along the Atlantic seaboard. Because the same sites, the same gear and the same seasonal window are used every year, the resulting index functions as a sensitive barometer of reproductive success, absorbing the noise of individual hauls and revealing the underlying signal of how many fish survived from egg to juvenile. That continuity is rare in marine science and makes the Chesapeake Bay dataset one of the longest-running juvenile fish surveys in the world.

The story of striped bass in the Chesapeake Bay is also a story of recovery, collapse and recovery again. The population fell to historic lows in the late 1970s and early 1980s, driven down by a combination of overfishing and environmental stress. In response, Delaware, Maryland and Virginia enacted fishing bans in the mid- to late-1980s, giving the species a reprieve during which spawning stocks could rebuild. The recovery was dramatic enough that by the mid-1990s striped bass in the Bay and along the Atlantic Coast were declared recovered, a milestone often cited as one of the great successes in American fisheries management. The moratorium years demonstrated that the species could rebound when given the chance, but they also set the stage for decades of heavy fishing that followed.

That renewed fishing pressure eventually caught up with the stock. Scientists determined that the striped bass population had again become overfished, with fishing-related mortality exceeding sustainable levels. The Atlantic States Marine Fisheries Commission, the interstate body that manages the species coastwide, addressed the situation in its 2024 Atlantic Striped Bass Stock Assessment Update Report, which concluded that the stock remains overfished but is no longer experiencing overfishing. In practical terms, that means the population is still below the threshold managers consider healthy, but the rate of removals has been brought down to a level that no longer prevents rebuilding.

Since 2022, a suite of management measures has been rolled out to push fishing mortality lower and rebuild the stock by 2029. Those measures include size limits on the recreational fishery, bag limits, gear restrictions and reductions in commercial quotas. Each tool targets a different segment of the fishery, and together they are designed to let more fish survive to spawning age and to give the 2025 and 2026 year classes room to grow into the breeding population. The 2026 juveniles measured this summer will begin recruiting to the recreational fishery in three to four years, meaning the success or failure of the rebuilding timeline will depend in part on how many of these fish survive their first years in the Bay.

Recruitment in striped bass is famously variable, and the reasons are complex. Young-of-year survival depends on the timing of spawning, water temperature, freshwater flows, the availability of zooplankton prey for larvae, and the abundance of predators in the nursery tributaries. Because so many factors interact, the index can swing from a few fish per haul to well over 20 in consecutive years without any change in the adult spawning stock. This is why fisheries scientists treat multi-year averages rather than single-year results as the meaningful metric, and why the alternating pattern of poor and strong year classes observed in the Virginia data is considered a normal feature of the population rather than a warning sign.

The picture across the state line is less encouraging. The Maryland Department of Natural Resources conducts a parallel seine survey in Maryland’s portion of the Chesapeake Bay, and in 2026 it recorded a below-average year class, the eighth consecutive year of below-average production in that jurisdiction. The divergence between the two states’ indices is not unusual, since the Maryland tributaries, particularly the upper Bay and the Choptank River system, respond to different environmental drivers than the Virginia rivers. Taken together, however, the two surveys provide the coastwide assessment with a Bay-wide index of spawning success, and the contrast between an average Virginia year class and a below-average Maryland one will factor into how managers weigh the strength of the overall 2026 cohort.

For now, the 2026 Virginia result offers a measure of reassurance for a fishery that has been under intense scrutiny. An average year class will not by itself rebuild the stock, but paired with the stronger 2025 class and the ongoing management restrictions, it suggests that the population is holding its ground while the rebuilding plan runs its course. Anglers, managers and scientists alike will be watching the 2027 survey to see whether the alternating pattern holds and whether the fish hatched this spring survive to bolster the spawning stock that the 2029 rebuilding deadline depends upon.

Subject of Research: Juvenile striped bass recruitment and population monitoring in the Chesapeake Bay

Article Title: Juvenile striped bass maintain average abundance in Virginia waters in 2026

Article References: Juvenile striped bass maintain average abundance in Virginia waters in 2026. Original publication (Bibliographic details unavailable.)

Image Credits: AI Generated

DOI: Not provided

Keywords: striped bass, Chesapeake Bay, Virginia Institute of Marine Science, seine survey, juvenile fish recruitment, fisheries management, Atlantic States Marine Fisheries Commission, stock assessment, year class, Maryland DNR, Juvenile, striped

The scale of the undertaking is remarkable. Scientific observers from the Mexican Institute for Sustainable Fisheries and Aquaculture measured and weighed a total of 8852 specimens representing eleven species from eight families of elasmobranchs, the class of cartilaginous fishes that includes all sharks and rays. The animals were captured during 55 trawling hauls conducted by commercial shrimp vessels between April 2013 and August 2017, across the continental shelf stretching from the mouth of the Río Bravo and the coast of Veracruz in the west to the Tabasco–Campeche Basin in the southeast. Each haul, conducted at night at depths between 9.1 and 90 meters, lasted between 1.8 and 7.0 hours as the nets dragged across the seafloor.

Why does such basic measurement work matter so much? Length–weight relationships, or LWRs, are among the most routinely used yet essential elements in fisheries science. They allow scientists to estimate biomass from length data alone, converting the average length of fish in a sample into the average weight, which is far more laborious to measure directly. They also let researchers convert length-based growth equations into weight-based ones and compare the physical condition of the same species across different regions or seasons. In practice, these equations are a critical component of stock assessment models, the analytical engines that determine how many fish can be sustainably harvested and how threatened populations might recover.

The mathematical foundation of the study is elegantly simple. The researchers fitted the classic power model, in which weight equals a constant times length raised to an exponent b, by regressing log-transformed weight against log-transformed length using the least-squares method. The constant a acts as a body shape coefficient, while the exponent b describes the type of somatic growth. When b equals exactly 3, growth is isometric, meaning the animal maintains its proportions as it grows. When b falls below 3, growth is negatively allometric, with the animal becoming more slender as it lengthens; when b exceeds 3, growth is positively allometric and the animal becomes stockier with size. Confidence intervals around b revealed which growth types could be statistically distinguished from isometry.

The results delivered a comprehensive picture of growth patterns across the southern Gulf’s demersal elasmobranch community. The allometric parameter b ranged from 2.5 to 3.2, entirely consistent with the expected range for fishes. Of the 23 estimations reported across pooled and sex-specific analyses, fifteen showed negative allometry, six showed isometry, and only two showed positive allometry: females of the butterfly ray Gymnura lessae and pooled samples of the bonnethead shark Sphyrna tiburo. Coefficients of determination, a measure of how well the model fits the data, exceeded 0.950 for every single species, meaning that weight can be predicted from length with remarkable accuracy.

Among the standout findings were four completely novel length–weight relationships for the lesser electric ray Narcine bancroftii, the skate Dipturus olseni, the roundel skate Rostroraja texana, and the guitarfish Pseudobatos lentiginosus. None of these species had ever had their length–weight relationship published before. In addition, the study provided the first Gulf of Mexico estimates for the southern stingray Hypanus americanus, G. lessae, the cownose ray Rhinoptera bonasus, the Atlantic angel shark Squatina dumeril, and the smooth dogfish Mustelus canis, while extending the known range of estimates for the bonnethead and the Gulf smoothhound Mustelus norrisi from the northern Yucatan Peninsula to the western Gulf.

Perhaps the most biologically intriguing discovery concerns the differences between the sexes. Using analysis of covariance, the researchers tested whether males and females of the six most abundant species followed the same growth curve. Five of the six species showed significant sexual dimorphism: females of R. texana, G. lessae, N. bancroftii, P. lentiginosus, and S. dumeril all carried more weight per unit of length than males, producing higher b parameters. Only the southern stingray bucked the trend, and the authors attribute this anomaly to a sampling quirk rather than biology. Larger female H. americanus exceeding 110 centimeters are less susceptible to shrimp trawling because turtle excluder devices fitted to the fleet’s nets tend to exclude the biggest individuals, blurring the expected pattern in the data.

The trawl fishery itself proved an unlikely but valuable scientific instrument. Because bottom trawls are poorly selective for species and size, especially for dorsoventrally flattened demersal animals like rays, the bycatch provided an unusually broad and representative size range for each species. The data covered eleven of the sixteen elasmobranch species known to occur in the shrimp trawl bycatch, which collectively account for roughly 3 percent of the total catch. Rays dominate this incidental harvest, contributing 82.4 percent of the bycatch biomass and 94.8 percent of its abundance, while sharks make up the smaller remainder. For most species the sample sizes were robust, exceeding 250 individuals, though five rarer species were represented by fewer than 100 specimens each.

Beyond the equations themselves, the study recorded new maximum sizes for two species, with female Rostroraja texana reaching 66.5 centimeters in total length, males 65.0 centimeters, and female Pseudobatos lentiginosus reaching 81.5 centimeters. Such records matter because maximum size constrains the upper bounds of population models and signals the demographic health of a species. The b values obtained for seven of the species were consistent with prior estimates from other parts of the Caribbean, the east coast of the United States, northeastern Brazil, and the Yucatan Peninsula, suggesting that these growth patterns are geographically stable and that the new parameters slot credibly into the broader Atlantic dataset.

The wider significance of this work lies in the conservation crisis facing sharks and rays. Elasmobranchs are among the most vulnerable marine taxa worldwide because their slow life histories, late maturity, and low reproductive rates make them acutely sensitive to fishing mortality. The Western Central Atlantic, including the Gulf of Mexico, has been identified as one of three global hotspots of threat to elasmobranch biodiversity, hampered by insufficient biological information and historical fishery data that lack taxonomic resolution. In Mexico, several of these species support artisanal fisheries, while others die unseen in trawl nets. By supplying the first biometric conversion factors for four species and the first Gulf-wide estimates for five more, the study directly serves Mexico’s research priorities under the Gulf of Mexico Fisheries Management Plan, giving managers the quantitative foundation they need to convert simple length observations into the weight estimates on which every modern stock assessment depends.

Subject of Research: Length–weight relationships of eleven demersal elasmobranch species from shrimp trawl bycatch in the southern Gulf of Mexico

Article Title: Length–weight relationships of eleven demersal ray and shark species ( Elasmobranchii ) from the southern Gulf of Mexico

Article References: Zea-de la Cruz, H., Meiners-Mandujano, C., Tovar-Ávila, J., Jiménez-Badillo, L., & Oviedo-Pérez, J. L. (2025). Length–weight relationships of eleven demersal ray and shark species (Elasmobranchii) from the southern Gulf of Mexico. Acta Ichthyologica et Piscatoria, 55, 191-195. https://doi.org/10.3897/aiep.55.156837

Image Credits: AI Generated

DOI: 10.3897/aiep.55.156837

Keywords: elasmobranchs, sharks, rays, Gulf of Mexico, length-weight relationships, fisheries science, shrimp trawl fishery, bycatch, allometric growth, stock assessment, conservation, Mexican fisheries

The research focused on Geographical Sub-Area 13, a fishing zone that encompasses Malta and the Lampedusa and Linosa islands and borders the Tunisian coast. At the heart of the assessment was the port of Teboulba, the single most important landing site for small tunas in the region. The harbor accounts for more than 15 percent of Tunisian marine fishery production and 71 percent of all declared fishery production within GSA 13, supporting over 2,800 direct jobs, many of them tied to the purse seine fleet that targets small tunas each spring and summer. Between March and November 2022, the researchers conducted 48 surveys at the port, measuring 916 individual fish taken directly from commercial landings: 408 little tunny and 508 bullet tuna.

What makes the study methodologically significant is its use of two complementary data-limited approaches, tools designed precisely for fisheries where the long, detailed datasets required by classical stock assessment models simply do not exist. The first, the Length-Based Bayesian Biomass method known as LBB, extracts surprisingly rich information from nothing more than the size distribution of caught fish. Because fish grow according to predictable patterns described by the von Bertalanffy growth function, the shape of a length-frequency distribution encodes how hard a stock is being hit. The descending slope of the distribution reflects total mortality, the position of the first peak reveals the size at which the gear begins catching fish, and the absence of large individuals signals that the oldest age classes have been stripped away. The second method, CMSY++, takes a completely different route: it reconstructs the trajectory of a stock from decades of catch records alone, using Bayesian Monte Carlo simulations to find the combinations of carrying capacity and intrinsic growth rate that could plausibly have produced the observed catches.

The two methods converged on a disturbing picture for the bullet tuna. LBB estimated that current biomass stands at just 8 percent of the unexploited level, with fishing mortality fifteen times higher than natural mortality, an extraordinary figure that leaves the population almost no buffer against environmental shocks. CMSY++, applied to 27 years of official landings from 1996 to 2022, confirmed the diagnosis: biomass sits at roughly half the level that would produce maximum sustainable yield, and fishing mortality exceeds the sustainable rate. In the language of the study’s classification scheme, the stock is not merely overfished but critically so, approaching collapse.

Equally alarming is what the size data revealed about the bullet tuna catch. Forty-two percent of the 508 specimens measured were smaller than the length at first maturity of 32.6 centimeters, meaning nearly half the catch consists of juveniles that have never had the chance to reproduce. The size distribution was bimodal, with peaks at 33 and 40 centimeters and a maximum observed length of just 44 centimeters, close to the species’ natural ceiling. This pattern suggests the fishery is intercepting fish during or even before the recruitment peak, putting the incoming generation directly under fishing pressure before it can contribute to stock renewal. Combined with the bullet tuna’s biology, which features rapid growth, early maturity, and a short lifespan that makes it dependent on successful annual recruitment, this juvenile harvest creates a recipe for the kind of boom-and-bust instability visible in the landings record, which swung from nearly 989 tonnes in 2003 to a mere 2 tonnes just two years later.

The little tunny tells a more nuanced story. Both assessment methods agree it is overfished and that overfishing is occurring, with CMSY++ placing biomass at three-quarters of the maximum sustainable yield level and fishing pressure about 39 percent above the sustainable rate. But its demographic structure is far healthier: only 2 percent of the sampled catch consisted of immature fish, and nearly all individuals captured had reached reproductive size. The fishery primarily takes medium-sized adults concentrated in the 55 to 59 centimeter class. Still, the study flagged a quieter warning sign: very large spawners exceeding 90 centimeters were rare in the samples, even though the species can grow to more than a meter in the Mediterranean. The researchers point to the well-documented importance of large, old, fecund females, which produce disproportionately more and better-quality offspring than younger fish. Their progressive disappearance erodes the resilience that the stock will need as fishing pressure continues.

The divergence between the two species is especially striking because they face identical fishing pressure, caught by the same purse seine fleet operating over the same grounds with the same gear. The researchers attribute the difference to a combination of life history traits and shifting fishing dynamics. Bullet tuna, which behaves more coastally and concentrates in predictable seasonal aggregations, is inherently vulnerable to concentrated purse seining. Little tunny, by contrast, appears to have benefited from the displacement of fishing effort that followed the introduction of strict quotas on Atlantic bluefin tuna, with Mediterranean landings peaking in 2016 and 2017, mirroring regional trends. Tunisia’s own record reflects this pattern: small tuna landings averaged around 2,813 tonnes between 1995 and 2010, with the bullet tuna and little tunny together accounting for roughly two-thirds of the catch.

The management implications are stark and species-specific. For the bullet tuna, the researchers recommend raising the minimum conservation reference size from the current 27 centimeters to 34 centimeters, the length that maximizes yield, alongside a genuine reduction in fishing effort and a seasonal closure during periods of high juvenile abundance in autumn and winter. For the little tunny, the priority is inverted: rather than protecting only the young, the fishery must protect the old. The study proposes prohibiting the landing of specimens larger than 80 centimeters and raising the minimum size from 54 to 66 centimeters, allowing fish to reach full reproductive potential. Remarkably, Tunisian legislation currently contains no minimum landing sizes or catch limits for either species, leaving them in a regulatory vacuum even as both are formally under the mandate of the International Commission for the Conservation of Atlantic Tunas, which has adopted no specific management measures for them either.

The study is not without uncertainties, and the authors are candid about them. Sampling covered a single year at a single landing site, retrospective analyses showed that the CMSY++ classification for the bullet tuna is sensitive to recent catch dynamics, and the absence of a Mediterranean-specific estimate of natural mortality for the species remains a critical data gap. Yet the core conclusions rest on unusually solid ground for a data-poor fishery: two independent methods built on entirely different data streams, length distributions and catch series, reached the same diagnosis for each species. The convergence itself demonstrates the feasibility of quantitative assessment for the many Mediterranean small tunas that have never been formally evaluated.

For a sea that holds 7 to 10 percent of the world’s marine species in less than 1 percent of the global ocean, the message extends well beyond two fish. Small tunas are vital sources of protein and income across the Mediterranean, and their transboundary migrations demand coordinated action through the GFCM and ICCAT frameworks. This study provides the scientific baselines that such coordination has lacked, and it delivers a clear deadline: without immediate, enforceable size limits and effort reductions, the bullet tuna of the central Mediterranean may become a cautionary tale of how quickly an overlooked species can slide toward collapse while everyone was watching the big tunas.

Subject of Research: Data-limited stock assessment of little tunny and bullet tuna in the central Mediterranean

Article Title: Stock assessment of small tunas, Euthynnus alletteratus and Auxis rochei ( Actinopterygii , Scombriformes , Scombridae ), in central Mediterranean (GSA 13): Implications for fishery management using data-limited approaches

Article References: Mili, S., Ennouri, R., Agrebi, S., Bejaoui, S., M. Morsi, M., Ben Ali, M., & Hedfi, A. (2026). Stock assessment of small tunas, Euthynnus alletteratus and Auxis rochei (Actinopterygii, Scombriformes, Scombridae), in central Mediterranean (GSA 13): Implications for fishery management using data-limited approaches. Acta Ichthyologica et Piscatoria, 56, 379-397. https://doi.org/10.3897/aiep.56.199776

Image Credits: AI Generated

DOI: 10.3897/aiep.56.199776

Keywords: small tunas, stock assessment, Mediterranean, data-limited methods, Euthynnus alletteratus, Auxis rochei, fisheries management, overfishing, CMSY++, LBB, purse seine, Tunisia

The study, published in Acta Ichthyologica et Piscatoria, focused on Geographical Sub-Area 12, a region corresponding to the northern Tunisian coast where fisheries data have long been too sparse and fragmented for conventional assessment methods. Researchers from Tunisian institutions tackled this data-poor problem by deploying a battery of complementary data-limited models, combining thirty years of catch records from 1995 to 2024 with nearly 1,900 individual fish measured at the port of Bizerte during 2024 and 2025. Sampling was conducted during night-time landings, when bottom trawlers return from their fishing trips, across 111 dedicated surveys spanning two years.

The biological portrait that emerges is of a species perfectly adapted to patience and ambush, and correspondingly vulnerable to exploitation. The best-fitting growth model, using the ELEFAN simulated annealing algorithm implemented in the TropFishR package, yielded an asymptotic length of 89.29 centimeters and a growth coefficient of 0.369 per year, indicating moderate growth with rapid early development that slows as fish approach their maximum size. Notably, the inclusion of a seasonal growth component did not improve model fit, suggesting that anglerfish in these deep, thermally stable Mediterranean waters grow continuously throughout the year rather than in seasonal bursts.

Perhaps the most consequential finding concerns reproduction and survival. The researchers estimated that half of the population reaches sexual maturity at 47.1 centimeters, with 95 percent mature at 56.52 centimeters, a relatively large size compared with the species’ maximum dimensions. Natural mortality came out remarkably low at 0.19 per year, based on the Hoenig estimator that links mortality to maximum observed age, which for this species reaches 24 years. This combination of late maturity, long lifespan and low natural death rates means the population’s fate rests almost entirely on fishing mortality rather than natural processes. Even modest changes in fishing effort can therefore ripple through the age structure and spawning biomass with disproportionate force.

The catch statistics themselves tell a striking story of an expanding fishery. Reported production rose from a mere 8 tonnes in 1995 to 93 tonnes in 2024, with a peak of 144 tonnes in 2019. Bottom trawling accounts for roughly 98 percent of the landings. Statistical analysis confirmed a significant upward trend of about 3.5 tonnes per year, corroborated by both linear regression and the non-parametric Mann-Kendall test, though the coefficient of variation of 73 percent reveals wild interannual swings that complicate any simple reading of the trajectory.

The heart of the assessment lies in four complementary models applied to these data. The CMSY++ Monte Carlo approach, which reconstructs stock biomass and fishing mortality from catch time series, estimated a biomass ratio of 1.18 relative to the level producing maximum sustainable yield, with fishing mortality at 0.904 of its sustainable benchmark. On paper, those numbers suggest a sustainably exploited stock. But the confidence intervals tell a more unsettling tale: the uncertainty range for the fishing mortality ratio extends from 0.445 all the way to 2.00, meaning that fishing mortality may in fact already exceed the sustainable threshold. The authors urge caution rather than celebration.

Length-based models added a demographic dimension to the picture. The length-based indicators method showed that only 46.5 percent of caught fish had exceeded the maturity length, far below the 100 percent target, while the proportion of mega-spawners, the large old females that contribute disproportionately to population renewal through higher fecundity and better egg quality, stood at just 10.15 percent against a precautionary reference of 20 percent. The Length-based Bayesian Biomass model reinforced the concern about size selectivity: fish are first caught at around 36 centimeters, well below the optimal capture length of about 47 centimeters, meaning the fishery harvests individuals before they have had their full reproductive opportunity.

The Length-Based Spawning Potential Ratio model, meanwhile, placed the stock right at the edge of the reproductive cliff. The spawning potential ratio was estimated at 39 percent in 2024 and 40 percent in 2025, hovering exactly at the 40 percent reference point generally regarded as the lower limit of full reproductive sustainability. In practical terms, the stock retains just enough spawning capacity to sustain itself, but possesses essentially no safety margin. The model also detected that fish become vulnerable to capture at slightly smaller sizes in 2025 than in 2024, a subtle signal worth monitoring. Sensitivity analyses showed the LBSPR results were robust to alternative biological inputs, but revealed that the LBB model’s encouraging biomass estimates could swing dramatically, from a biomass ratio of 1.60 down to 0.18, when different published growth parameters were substituted, underscoring how much rides on getting the biology right.

How does the Tunisian population compare with its relatives elsewhere? The Mediterranean fish grow faster but reach smaller maximum sizes than their northeastern Atlantic counterparts, where asymptotic lengths can exceed 200 centimeters and growth coefficients fall as low as 0.05 per year. This pattern fits the temperature-size rule: warmer, nutrient-poor Mediterranean waters accelerate early growth but cap ultimate size. Intriguingly, the estimated theoretical age at zero length of -0.33 years aligns closely with values from the Irish Sea, Norway and Iberian waters, suggesting the fitted growth curve accurately captures the species’ early life phase even in this under-studied region.

The overall verdict is deliberately nuanced: the stock shows no signs of severe depletion, yet the evidence does not allow it to be classified as sustainably exploited. The authors recommend a precautionary approach centered on three pillars: holding fishing mortality at current levels rather than allowing any increase, improving gear selectivity so that smaller individuals escape, and protecting the large spawners whose loss would erode the stock’s resilience. Concrete options include raising the minimum landing size above the current first-capture length of 36 centimeters and strengthening data collection on effort and catch composition. For a species whose survival strategy is to wait motionlessly on the seafloor for prey to wander within reach, the white anglerfish now finds itself in a similar position, one wrong move by the fishery could leave it without the spawning biomass it needs to recover.

Subject of Research: Population dynamics and data-limited stock assessment of the white anglerfish Lophius piscatorius in the central Mediterranean Sea

Article Title: Population dynamics and stock assessment of the white anglerfish, Lophius piscatorius ( Actinopterygii , Lophiiformes , Lophiidae ), in the central Mediterranean Sea (GSA 12)

Article References: Agrebi, S., Ennouri, R., Alayet, F., Hedfi, A., Louiz, I., Ben Ali, M., Mahmoudi, E., & Mili, S. (2026). Population dynamics and stock assessment of the white anglerfish, Lophius piscatorius (Actinopterygii, Lophiiformes, Lophiidae), in the central Mediterranean Sea (GSA 12). Acta Ichthyologica et Piscatoria, 56, 441-459. https://doi.org/10.3897/aiep.56.209443

Image Credits: AI Generated

DOI: 10.3897/aiep.56.209443

Keywords: white anglerfish, Lophius piscatorius, stock assessment, data-limited fisheries, Mediterranean Sea, Tunisia, CMSY++, LBSPR, length-based indicators, fisheries management, demersal species, spawning potential ratio

The study was led by Jerald S. Ault, professor emeritus at the University of Miami Rosenstiel School of Marine, Atmospheric, and Earth Science, together with co-author Jiangang Luo, a scientist at the Rosenstiel School’s Cooperative Institute for Marine and Atmospheric Studies. Rather than collecting new field data, the pair returned to the raw records of a landmark federal tagging experiment conducted from 1966 through 1971, an enormous undertaking that spanned the Atlantic coast from Massachusetts to Florida and involved more than one million tagged menhaden and more than 100,000 recovered tags. By reconstructing that historic dataset from the ground up, the researchers uncovered discrepancies that, once corrected, fundamentally changed the mortality estimate that flows through modern management models.

Natural mortality is one of the most influential and least directly observable inputs in any fish stock assessment. It represents deaths from predation, disease, old age, and environmental stress, and it is typically estimated rather than measured. When that rate is set too high, the mathematics of assessment models effectively attribute a larger share of total deaths to nature and a smaller share to the fishing fleet. The result is an optimistic picture: the spawning stock appears larger and more productive than it really is, and the models generate harvest advice that the population’s underlying biology may not be able to support. For a forage species sitting at the base of the coastal food web, that optimism ripples outward to every predator that depends on it.

The stakes are illustrated by the numbers themselves. The new analysis estimates natural mortality for Atlantic menhaden at approximately 0.50 per year, meaning that in an unfished population roughly half of the fish would be expected to die each year from natural causes. That figure is less than half of the 1.17 estimate reported in a 2019 reanalysis by Liljestrand and colleagues, which was incorporated into the SEDAR 69 benchmark stock assessment used by the Atlantic States Marine Fisheries Commission. It is also substantially below the corrected value of 0.92 adopted in a 2025 stock assessment update. In practical terms, the difference between these values determines how much of the population’s decline managers are willing to blame on fishing rather than on nature.

Reconstructing the historic tagging experiment was a forensic exercise. Over approximately three years, Ault and Luo rebuilt two independent versions of the historical dataset, cross-checked the counts of fish released and tags recovered, reconstructed the fishing effort records for the era, and examined in detail how metal tags were actually detected when harvested fish arrived at processing plants. The investigation identified discrepancies involving the numbers of released and recovered tagged fish, the reconstruction of historical fishing effort, the treatment of tag-detection efficiency at the plants, and aspects of the statistical model used to interpret the recovery data. Each of these issues, the authors found, had the potential to bias the mortality estimate, but one proved decisive.

That decisive factor was the performance of the magnets used to recover the metal tags embedded in harvested menhaden. In the original experiment, tagged fish were detected as they moved through reduction plants along the coast, where conveyor-belt magnets were supposed to pull tagged carcasses out of the processing stream. Detection efficiency, however, varied widely from plant to plant and from month to month, depending on equipment, throughput, and operating conditions. Earlier analyses that assumed a uniform detection rate across this heterogeneous system would have systematically miscounted how many tagged fish were actually recovered, distorting the apparent survival of the tagged population and inflating the estimated rate of natural death.

When the researchers built statistical models that allowed tag-detection efficiency to vary by location and by month, the fit to the recovery records improved markedly. Both of the independently reconstructed datasets produced natural mortality estimates near 0.50 per year, a striking convergence given that the two reconstructions were built separately from the original federal records. The team then ran additional computer simulations to test how sensitive the results were to uncertainty in the underlying assumptions, and the best-fitting outcomes consistently supported a similar value. The estimate also aligned with earlier research and biological evidence indicating that Atlantic menhaden historically lived at least ten years, a longevity that is difficult to reconcile with a very high natural mortality rate, since fish dying at a rate of more than one per year would rarely survive that long.

The authors are careful to frame what the finding does and does not mean. The study concerns a historical estimate of natural mortality, not a newly observed change in the survival of today’s menhaden stocks. It does not establish a new catch limit, and it does not claim that recent population trends have been misreported. What it does argue is that the input value used in the assessment framework should change. Ault and Luo recommend that future stock assessments evaluate natural mortality values centered at 0.50 per year while explicitly accounting for the uncertainty surrounding that estimate, rather than anchoring the models to the substantially higher rates adopted in the 2019 reanalysis and the 2025 update.

The management implications are potentially far-reaching. If natural mortality is high, fishing appears to account for only a small share of population change, and harvest limits can be set generously without much apparent risk. If natural mortality is closer to 0.5, as this study and earlier historical estimates suggest, fishing may account for a considerably larger share of the losses, and the same level of harvest represents a heavier burden on the stock. For Atlantic menhaden, a species that is both heavily harvested by one of the region’s largest reduction fisheries and ecologically central as prey for managed predators such as striped bass, that distinction matters not only to the menhaden fishery itself but to the entire chain of coastal ecosystems and fisheries that depend on abundant menhaden schools.

The study, titled Investigation of Atlantic menhaden mortality rates, demonstrates how revisiting the raw data behind decades-old experiments can still reshape contemporary science policy. Tagging studies from the 1960s were conducted with different technology, different quality controls, and different statistical tools than those available today, and the assumptions baked into their original analyses can persist unexamined through successive rounds of assessment. By showing that a single overlooked source of measurement error, the uneven performance of recovery magnets at processing plants, could shift a pivotal mortality estimate by more than half, the work underscores a broader lesson for fisheries science: the numbers that guide harvest decisions are only as reliable as the historical records and statistical assumptions beneath them, and those foundations deserve periodic re-examination, especially when the species in question anchors an entire coastal food web.

Subject of Research: Reanalysis of historical tagging data to re-estimate natural mortality rates of Atlantic menhaden for fisheries management

Article Title: Study challenges estimates used to guide Atlantic menhaden fishing

Article References: Study challenges estimates used to guide Atlantic menhaden fishing. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: Atlantic menhaden, natural mortality, fisheries management, stock assessment, tagging study, forage fish, Fisheries Research, Atlantic States Marine Fisheries Commission, SEDAR 69, tag detection efficiency, coastal food web, University of Miami Rosenstiel School

The research team, led by Steven Saul and including scientists from The Nature Conservancy, Yayasan Konservasi Alam Nusantara, Indonesia’s Ministry of Marine Affairs and Fisheries, and the University of Rhode Island, confronted a core dilemma of tropical fisheries science: most of these fisheries are too poorly documented for conventional assessment. Data-limited methods, which squeeze advice from sparse catch records and fish length measurements, are the only realistic option, but they vary widely in the estimates they produce from the same data. Rather than relying on any single model, the team combined five different fishing mortality estimators, including length-based spawning potential ratio methods, the LIME framework, Beverton-Holt total mortality estimation with bias correction, catch curve analysis, and a solution of Baranov’s catch equation. Biomass was estimated with the catch-only Catch-MSY approach, wrapped in four sensitivity scenarios around catch history and depletion assumptions.

Uncertainty was layered even deeper. The analysts paired these biomass and mortality models with five alternative life history parameter sets, drawn from FishBase, from the FishLife predictive database, from the study’s own length data, and from calculations five percent above and below those data-derived values. Every permutation of model, life history scenario, and biomass scenario — which the authors call “states of nature” — was carried through the entire workflow to reconstruct population demographics and forecast numbers at age forward in time. The result is an assessment in which both model uncertainty and data uncertainty flow directly into the confidence bounds reported for every stock status estimate, a deliberate design choice meant to communicate honest ranges rather than false precision.

The findings, presented in Kobe plots and boxplots pooled across management areas, are sobering despite their uncertainty. Most model scenarios indicate that fishing is occurring above the target reference point, defined as the fishing mortality that maintains a stock at a spawning potential ratio of 40 percent. Approximately 60 percent of the assessed species have biomass below their limit reference point, the biomass corresponding to a 20 percent spawning potential ratio. Snappers, drums, croakers, and some emperor species fell below the limit, while groupers and grunts were estimated to remain above it. Across all Fisheries Management Areas, roughly half of the assessed species had biomass under the limit benchmark and about three-quarters were being fished harder than the target rate, although the authors caution that substantial uncertainty surrounds these figures.

What distinguishes the study is its translation of stock status into decision-relevant trade-offs. The team evaluated six management alternatives: continuation of current fishing mortality, and managing each stock at fishing rates sustaining spawning potential ratios of 20, 30, and 40 percent, maximum sustainable yield, or maximum economic yield. For each option, they estimated rebuilding times, equilibrium catches, profit, and nutritional composition of the catch. Rebuilding is fastest, within roughly five to 10 years, if fishing is held to the F@SPR40 percent benchmark, while continuing to fish at the SPR 20 percent or maximum sustainable yield levels would delay recovery to about 15 to 20 years for stocks currently below their limit.

Equilibrium catches once stocks recover are remarkably similar across benchmarks, ranging from about 70,000 to 88,000 metric tons per year. The species composition of that future catch also changes little between scenarios. The economics tell a sharper story: fishing at current mortality rates is projected to produce a financial loss, driven largely by the Malabar snapper, Lutjanus malabaricus, the fishery’s primary target species, which is being fished above its target while its biomass sits below the limit. Managing the fishery at any of the sustainability benchmarks turns profit positive once depleted stocks rebuild, with the largest profits realized at maximum economic yield and at the SPR 30 percent benchmark.

Nutritional outcomes, calculated by applying the Nutracast model to forecast catch composition, show little difference across management scenarios once stocks are rebuilt, because the species mix of the equilibrium catch is fairly consistent. But the authors warn that this stability cannot be taken for granted. If costs continue to exceed revenues and stocks remain below their limits, catches could decline in future years, eroding the fishery’s contribution to food security. About 80 percent of Indonesia’s snapper and grouper production is sold domestically, and it remains unclear how much of the retained harvest reaches Indonesian consumers versus the tourism sector, or how it divides between subsistence use, market purchases, and low-grade fish parts retained by fishers and processing workers.

The socioeconomic dimension adds further nuance. Recovering overfished stocks requires reducing fishing pressure, which imposes near-term costs on fishing communities in the world’s second-largest wild-capture fish producing nation. The authors recommend a slow, phased approach with very small, incremental reductions, giving fishers time to adapt by changing target species, gear configuration, or livelihoods. They also explore the hypothetical consequences of restricting landings of Lutjanus malabaricus alone, noting that the species could act as a “choke” constraint: fishers might switch to other species, discard regulated catches and cause discard mortality, or exit the fishery, potentially leaving healthy stocks underutilized. Because the other main species, Pristipomoides multidens and P. typus, overlap spatially with Malabar snapper, managing the dominant species would inevitably affect the rest of the catch.

The study is candid about its limitations. Length samples and landings were assumed to be uniformly distributed within each management area, yet sampling is shaped by where vessel captains choose to fish, with GPS trackers from participating vessels showing repeated visits to the same locations. Local depletion and targeting of plate-sized fish can bias mortality estimates, and gear selectivity in this mixed-gear fishery is only partially modeled. The catch-only biomass method rests on strong assumptions, including the use of a length-based spawning potential ratio as a proxy for depletion, which the authors acknowledge is not strictly equivalent. Trophic-level analysis found no correlation between a species’ position in the food web and its stock status, hinting that exploitation spans all trophic levels rather than progressing from top to bottom, though the sampled species covered only trophic positions three to five.

Ultimately, the study’s contribution is methodological as much as substantive. It demonstrates that even where formal assessments are impossible, a carefully combined ensemble of data-limited models with systematic sensitivity testing can deliver tactical management advice, complete with quantified uncertainty and explicit trade-off tables, suitable for structured decision-making. The authors emphasize that the results are shared to inform, not dictate, policy: decisions rest with Indonesian resource managers and stakeholders through the country’s legally established processes. The analysis code is publicly available on GitHub, and the underlying data collection system, the Crew Operated Data Reporting System, relies on commercial fishers themselves recording the lengths of their catch — a partnership the study’s authors say is essential to building the data streams that will steadily narrow the uncertainty surrounding one of the world’s most important tropical fisheries.

Subject of Research: Biological, economic, and nutritional trade-offs of management reference points in Indonesia's data-limited tropical demersal snapper and grouper fishery

Article Title: Biological, economic and nutritional trade-offs in tropical information limited fisheries: Indonesia's demersal finfish

Article References: Saul, S., Carrella, E., Carroll, G., Satria, F., Sadiyah, L., Mous, P., Perdanahardja, G., Ekawaty, R., Ananthanarayanan, A., Bailey, R., Dorsett, C., Drexler, M., Humphries, A., & Wibisono, E. (2026). Biological, economic and nutritional trade-offs in tropical information limited fisheries: Indonesia's demersal finfish. Environmental and Sustainability Indicators, 32, Article 101492. https://doi.org/10.1016/j.indic.2026.101492

Image Credits: AI Generated

DOI: 10.1016/j.indic.2026.101492

Keywords: data-limited fisheries, Indonesia, snapper, grouper, stock assessment, demersal finfish, spawning potential ratio, maximum sustainable yield, maximum economic yield, food security, fisheries management, Lutjanus malabaricus