Fisheries Management Tool Research Articles

Relating fish populations to coral colony size and complexity

A goal of coral reef management is to provide habitat and nursery areas for fish populations. This requires simple and reliable methods for characterizing biological and physical reef features that contribute to fish habitat. Most attempts to establish this relationship have been performed on small-scale, site-specific study areas where variability in fish populations and reef structure is limited and results may be insufficiently robust for extrapolation beyond those sites. Most studies also include geological structures, like ridges and rock formations that provide fish habitat but are not amenable to management action. A focus on the role of Scleractinia (stony corals) may better inform decisions aimed at improving fish habitat. Stony corals provide the structural foundation of coral reefs and are the target of numerous management actions. Data from three broad-area, multi-station reef surveys of fish and stony coral colonies were examined to identify correlations between fish population measures (density, taxa richness and biomass) and both biological (taxa richness and live surface area) and physical (number, size and structural complexity) attributes of scleractinian coral populations. Strongest correlations were found with physical coral features, particularly coral colony height. Characterizing this relationship will improve fishery management tools and support status and trend assessment of the worldwide decline in the physical stature of reefs.

Optimal dynamic spatial closures can improve fishery yield and reduce fishing-induced habitat damage

Bottom-towed fishing gears produce significant amounts of seafood globally but can result in seafloor habitat damage. Spatial closures provide an important option for mitigating benthic impacts, but their performance as a fisheries management policy depends on numerous factors, including how fish respond to habitat quality changes. Spatial fisheries management has largely focused on marine protected areas with static locations, overlooking dynamic spatial closures that change through time. To investigate the performance of dynamic closures, we develop a spatial fishery model with fishing-induced habitat damage, where habitat quality can affect both fish productivity and movement. We find that dynamic spatial closures often achieve greater harvest and habitat protection than fixed marine protected areas or conventional nonspatial maximum sustainable yield management, especially under strong habitat–stock interactions. Determining optimal dynamic spatial closures may require considerable information, but we find that simple policies of fixed-schedule rotating closures also perform well. Dynamic spatial closures have received less attention as fisheries management tools, and our results demonstrate their potential value for addressing both harvest and habitat impacts from fishing.

Fisheries and stock assessment of the European hake in GSA 04 zone (Algerian eastern coast) - tools for fisheries management and conservation

Fisheries and stock assessment of the European hake in GSA 04 zone (Algerian eastern coast) - tools for fisheries management and conservation

When the Trawl Ban Is a Good Option: Opportunities to Restore Fish Biomass and Size Structure in a Mediterranean Fisheries Restricted Area

This paper reports the results of a 15-year trawl ban imposed in 1990 in the Gulf of Castellammare (GCAST: NW Sicily, central Mediterranean Sea) and its effects on the biomass and size structure of demersal finfish and shellfish and on the proportion of different commercial categories of fish. Data were collected by experimental trawl surveys conducted in the GCAST and in two trawled areas before and after 1990. The biomass of the total assemblage and of a number of selected species was significantly higher in the GCAST after the ban. Highly commercial species had the largest increase in the same gulf after the ban, particularly at the depths used by artisanal fishermen. The results from size-based indicators were not as clear-cut as those from biomass though. Although the length frequency distributions obtained in the GCAST were significantly different from the other gulfs, in several cases, the values of the size indicators were higher in the trawled gulfs. Our results suggest that, at the temporal and spatial scale adopted, trawl bans may drive full biomass recovery but only partial size structure recovery of the fish populations subject to trawl exclusion, at least in the Mediterranean. The trawl ban in the Gulf of Castellammare provides an example of an effective ecosystem-based fisheries management tool that offers the potential for fish stock rebuilding and for the economic sustainability of artisanal, small-scale fisheries.

Evaluating 87Sr/86Sr and Sr/Ca ratios in otoliths of different European freshwater fish species as fishery management tool in an Alpine foreland with limited geological variability

The focus of this study was to assess the potential of otolith microchemistry as a fishery management tool for different European freshwater fish species in an Alpine foreland with a diverse range of different water bodies but low geological variation. 87Sr/86Sr isotope ratios and Sr/Ca ratios in water samples from 26 habitat sites in a pre-alpine catchment region around lake Chiemsee, Germany, an important region for recreational and economic fisheries, were analysed. 87Sr/86Sr isotope ratios and the Sr/Ca ratios in otoliths of 246 fish out of 16 species were determined using (laser ablation) inductively coupled plasma mass spectrometry ((LA)-ICP-MS). Habitats could be differentiated into seven clusters when using the 87Sr/86Sr isotope and Sr/Ca ratios in water in combination. When using the 87Sr/86Sr isotope ratio as individual parameter, the strontium isotope groups (SIGs) based on the 87Sr/86Sr isotope ratios including the measurement uncertainties justified a three-cluster solution. The direct comparison of 87Sr/86Sr isotope ratios in water and otolith samples allowed to identify fish that a) might have migrated, b) were transferred from other water bodies or c) stocked from fish farms. Sr/Ca ratios in water and otoliths were highly correlated, although significant differences between species from the same environment were documented. Sr/Ca ratios in sagittae of Perca fluviatilis were about 64–60% of those in sagittae of Coregonus spp and of lapilli of roach Rutilus rutilus from the same habitats, respectively. Partition coefficients for water to otolith Sr/Ca ratios were calculated and differed between species. Discrimination of fish otoliths according to habitat clusters by combining 87Sr/86Sr and Sr/Ca ratios was possible with success rates of up to 100% for whitefish Coregonus spp., 90% for European perch Perca fluviatilis, 87% for cyprinids, and 89% European grayling Thymallus thymallus, and 68% for salmonids. When using the 87Sr/86Sr isotope ratios as single parameter, assignment results were generally worse, except for salmonids, where an improved accuracy of 79% could be achieved, or for cyprinids when the number of clusters was reduced from five to three. The study indicates that otolith microchemistry has great potential to serve as a fishery management tool at smaller spatial scales such as in the studied Alpine foreland when combining the 87Sr/86Sr and Sr/Ca ratios, and considering the type and spatial distribution of habitats, the species and question under investigation.

Advantages and Disadvantages of Rotating Spatial Closures for Managing Fisheries

Marine protected areas are becoming an increasingly important tool in fisheries management. Particularly for species with relatively sedentary adults, the basic approach taken is to permanently close areas to fishing, which allows species to recover inside the reserve and export larvae to outside of it that can eventually be harvested. Two key issues posed are ensuring the movement of larvae outside the reserve to support fisheries and the sociological and economic impact of marine reserves. An alternative approach that addresses these issues is rotational zoning systems, which have been implemented for some fisheries. What has been missing is an analysis of the relative impact of marine reserves versus rotational zoning systems on fisheries yields that could be used to provide important principles to guide management. Using a simplified model with clear assumptions, we show that rotational zoning systems are inferior in fisheries management targeting low-fecundity species or species with a low proliferation rate, especially when the fraction of the coastline protected is relatively small (approximately less than 20%) and the rotational fraction results in landings far below optimal fisheries yields. These results are tested with hypothetical species, providing quantitative guidelines in cases where decisions must be made with limited data as well as a framework for more detailed analyses in cases where more data are available.

Population dynamics of the European native oyster in a Marine Conservation Zone exposed to unregulated harvesting

The implementation of closed zones as fishery management tools have been shown to be successful in the augmentation of habitat restricted species. A concerted restoration effort is currently being focused on the European native oyster throughout its natural range. This has been accompanied by an increase in oyster prices. In 2018 a native oyster for restoration purposes cost 80 pence sterling by 2021 the price had increased to £3.50. It is likely that these price increases have led to harvesting pressure on established wild populations. A number of recovering Ostrea edulis assemblages in Strangford Lough Northern Ireland are located within a closed zone which has been in operation since 2008. This research investigated the effectiveness of this restricted area in regards to protecting O. edulis assemblages. The study revealed that within policed regions of the restricted area the population increased from an estimated 1000 oysters in 2004 to >88,000 in 2021. Furthermore, the age structure and population dynamics differed considerably from non-policed areas which still experienced harvesting. The research supports the use of closed zone legislation as a conservation tool with developing O. edulis populations. As newly restored populations become established, rising market prices will place these under increased harvesting pressure. The use of closed zones may offer a means of protecting these emergent populations.

Gender awareness and perception on Marine Protected Areas (MPAs) in Taytay, Palawan, Philippines

Marine Protected Area (MPA) is a recognized tool for conservation and fisheries management. In the Philippines, there are around 1,800 locally-managed MPAs and 155 are in Palawan. However, gender knowledge and perceptions on their impacts on communities and the environment are poorly documented. Thus, this study was conducted to determine the gender awareness and perception on MPAs’ functions, benefits, and status of coastal communities in Taytay, Palawan, Philippines. The socio-demographics of the respondents and their effects on perceptions were also investigated. There were 401 respondents but only 108 were considered for analysis after data cleaning. About 60% are men and 40% are women. A total of 16 questions on MPA awareness and perceptions were asked during the interview that utilized KoboToolBox. The data were analyzed using General Linear Model, and Principal Component Analysis. Results showed that awareness varied between genders with men being more aware of the existence of MPAs (82%) and its programs (72%). However, both have almost the same level of perception on benefits from MPAs. Men and women perceived MPAs to have helped in conservation like improving biodiversity, but not on providing direct economic benefits such as an increase in catch and income. These indicate that their perceptions on MPAs were generally theoretical, rather than actual. Further, men’s perceptions were significantly affected by age and ethnicity while women’s perceptions were not affected by any of their socio-demographics.

The effectiveness of bite-shortened hooks for reducing handling time and injury of small-bodied freshwater fish captured by recreational anglers

Modified bite-shortened hooks show promise for enabling easy handling and rapid release of fish captured by recreational anglers, with the potential to reduce injury and stress of released fish. This study investigated whether bite-shortened modified hooks were effective at improving fish welfare relative to more traditional hook configurations. We evaluated how hook type (jigs vs. Aberdeen), hook length (regular, shortened by 4 mm or shortened by 6 mm), and the presence or absence of a barb influenced the landing rates, handling time, hooking depth, ease of hook removal, and injury of Bluegill (Lepomis macrochirus). There was significantly more fish landed using jig style (87.7%) than Aberdeen hooks (80.5%). The landing rates varied significantly among hook configurations with standard barbed hooks having the highest landing success (96%) and very bite-shortened hooks having the lowest (67%) landing success. Once landed, self-release (i.e., unhooked without use of hands) was most common for fish caught on very bite-shortened (shortened by 6 mm), followed by short bite-shortened (shortened by 4 mm), and then regular barbless hooks (hook not modified), while regular barbed hooks had the lowest self-release rate. Very short bite-shortened and short bite-shortened barbless hook configurations resulted in shallower hook depths and were less likely to cause injury compared to barbed and barbless regular length hooks. This research suggests that bite shortened barbless hooks allow for easy and rapid self-release while retaining reasonably high rates of landing success, suggesting that bite-shortened hooks could be a useful management tool for recreational fisheries.

Species-specific molecular signatures for the commercially important scombrids using mitochondrial gene analysis; a tool for fisheries management

The family Scombridae, comprising of commercially important marine fishes, which are widely distributed across tropical, subtropical, and temperate waters. Scombrids constitute an important fishery and are exploited across their range of distribution. Accurate identification of species is important for effective fisheries management and forensics purposes. In the present study, commercially important species of scombrids distributed in Indian waters were selected for molecular phylogeny and development of species-specific diagnostic keys using mitochondrial cytochrome c oxidase I (COI) gene. In addition to morphological identification, the species were identified using molecular-based identification approach and character-based identification system. Molecular phylogeny for 16 species of scombrids was ascertained using mitochondrial COI analyses. The character-based molecular diagnostic keys for 16 species of scombrids were developed in-silico from data set comprising 603 mtCOI sequences generated in the present study as well as collected from published resources. The study uncovered 39 unambiguous molecular keys, capable of distinguishing all reference taxa under study. The development of species-specific sequences and key diagnostic nucleotides for scombrid fish species will be helpful in effective forensic applications, enforcement of fisheries regulations, and for sustainable utilization of this commercially important group of species.

Larval Retention and Homing Behaviour Shape the Genetic Structure of the Bullet Tuna (Auxis rochei) in the Mediterranean Sea

Background: The bullet tuna (Auxis rochei) is an epipelagic fish with a worldwide distribution that is highly targeted by fisheries. Genetic diversity and population genetics are good indicators of population structure and thus, essential tools for fisheries management. Knowing which factors (biotic and abiotic) might be shaping such structure is crucial for management plans. In the present study, we assessed the population structure of the bullet tuna in the western and central Mediterranean Sea. Methods: We used two types of genetic data: the mitochondrial DNA control region and seven microsatellite loci. The analysis of 431 sequences with a length of 386 bp from the mtDNA CR and the results from 276 individuals were genotyped by seven microsatellite loci. Results: Both types of markers coincided in showing significant genetic differences between an Iberian Peninsula–Strait of Gibraltar stock in comparison with a North African stock. Conclusions: We argue that this differentiation pattern is likely caused by reproductive strategies such as coastal spawning, larval retention, and natal homing behavior. These results should endorse the implementation of management plans for a resource that currently is not being managed. Thus, to ensure sustainability, these new policies should consider the presence of at least two genetically identified stocks.

Coastal aquaculture farms for the sea cucumber Apostichopus japonicus provide spawning and first-year nursery grounds for wild black rockfish, Sebastes schlegelii: A case study from the Luanhe River estuary, Bohai bay, the Bohai Sea, China

Aquaculture farms are known to attract wild organisms from nearby areas. Sea cucumber Apostichopus japonicus aquaculture farms in Bohai Bay, the Bohai Sea, China, might provide spawning and nursery grounds for wild black rockfish Sebastes schlegelii populations. To identify the above, we studied the variation in the numbers of S. schlegelii larvae (and length-categories as a percentage of the natural population) via ichthyoplankton surveys by months from January to October 2020, and assessed the food web structure and energy flow distribution of the farm and trophic links of S. schlegelii natural stock by using Ecopath modeling in July 2016 to August 2017. Larvae with a length between 3.90-5.80 mm were observed in the farm in May 2020, the juveniles with an estimated trophic level of 4.31. Juveniles used the farms as first-year nursery ground, and then they swam into deeper waters in August of the following year. MTI analysis showed increasing biomass of S. schlegelii might result in a decrease in the biomass of crustacea, and had positive and negative impacts on mollusk and Hexagrammos otakii biomass. We argued that aquacultural infrastructures constructed by artificial reefs could be used as a fisheries management tool to enhance S. schlegelii stocks and that monitoring of other marine organisms, such as oysters, Rapana venosa, Charybdis japonica, and Asterias spp. etc., was necessary to maintain sustainable exploitations of aquacultural farm ecosystems. A paucity of knowledge surrounding the interactions between aquaculture farms and wild organisms needs furthermore researches.

Ten years of dynamic co-management of a multi-species reef fishery

Co-management, a governance process whereby management responsibility is shared between resource users and other collaborators, is a mainstream approach for governing social and ecological aspects of small-scale fisheries. While many assessments of co-management are available for single time periods, assessments across longer time-scales are rare–meaning the dynamic nature, and long-term outcomes, of co-management are insufficiently understood. In this study we analyse ten-years of catch and effort data from a co-managed, multi-species reef fishery in Solomon Islands. To further understand social, ecological and management dynamics we also draw on interviews with fishers and managers that had been conducted throughout the same decade. We aimed to answer (1) what are the temporal trends in fishing effort, harvesting efficiency, and catch composition within and beyond a periodically-harvested closure (i.e. a principal and preferred management tool in Pacific island reef fisheries), and, (2) what are the internal and external drivers that acted upon the fishery, and its management. Despite high fishing effort within the periodically-harvested closure, catch per unit effort remained stable throughout the ten years. Yet the taxonomic composition of catch changed substantially as species targeted early in the decade became locally depleted. These observations indicate that both the frequency of harvesting and the volumes harvested may have outpaced the turnover rates of target species. We argue that this reflects a form of hyperstability whereby declining abundance is not apparent through catch per unit effort since it is masked by a shift to alternate species. While the community sustained and adapted their management arrangements over the decade as a response to internal pressures and some signs of resource changes, some external social and ecological drivers were beyond their capabilities to govern. We argue the collaborative, knowledge exchange, and learning aspects of adaptive co-management may need even more attention to deal with this complexity, particularly as local and distal pressures on multi-species fisheries and community governance intensify.Graphical abstract

Proof-of-Concept Studies Demonstrate That Food and Pheromone Stimuli Can Be Used to Attract Invasive Carp So Their Presence Can Be Readily Measured Using Environmental DNA

The utility of environmental DNA (eDNA) as a detection tool for fisheries management is limited by dilution and degradation, especially in areas of low fish abundance. This proof-of-concept study addressed these challenges by testing whether food or pheromones might be used to attract invasive carp so they can be measured more readily using eDNA. In two experiments, PIT-tagged carp were stocked into ponds (N = 3 for silver carp; N = 1 for common carp) while one of two stimuli (planktonic food [spirulina] for silver carp and a sex pheromone [prostaglandin F2α] for male common carp) was added to determine if we could attract fish to one side while measuring both fish presence (detections) and eDNA concentrations. The addition of spirulina increased detections of silver carp by 2–3 fold, while eDNA concentrations increased by 4-fold on the test side when compared to the side without the stimulus. The addition of the sex pheromone increased detections of common carp by ~25-fold, where a 6-fold increase in eDNA concentrations was measured (p < 0.05). A strong positive correlation was noted between fish presence and eDNA concentration for both species. These experiments demonstrate that food and pheromone stimuli could be used to attract invasive carp so they could be measured more easily and accurately.

Expanding narratives of governance constraints to improve coral reef conservation.

To understand and address the failures of reef governance, it is critical to understand the perceptions of diverse policy makers and practitioners about the challenges they face in achieving their goals. Examining the discourse of policy makers and practitioners can reveal the extent to which these perceptions capture the full spectrum of potential governance challenges, including those related to management, institutional structures and processes, the values and principles underpinning governance, and the social and environmental context. We conducted semistructured interviews with 110 policy makers and practitioners across multiple sectors, scales, and contexts in Barbados, St Kitts and Nevis, Belize, and Honduras. We used thematic qualitative analysis informed by theories of interactive governance and governability to examine the challenges perceived by governance actors. Perceived governance challenges were broadly consistent across countries, but differed by sector (V = 0.819, F6,60 = 1.502, p = 0.01) and by level (community compared with national) (V = 0.194, F1,10 = 2.178, = 0.026). Management inputs and outputs, challenges relating to the socioeconomic context, issues of leadership and power, and stakeholder engagement were commonly cited challenges (>75%). Few respondents discussed challenges relating to the ecological context, governance processes, or the values and principles underpinning governance. We argue that examining perceptions can inform efforts to improve governance and assess the appropriateness of particular management tools under context-specific governance constraints. Furthermore, expanding the narratives of governance challenges to encompass the subtle values and images underpinning governance, and the scale of the challenges faced, can help identify a wider set of opportunities for change.

To eat or not to eat, coastal sea trout anglers’ motivations and perceptions of best practices for catch and release

The wide variety of perspectives and actions of individual anglers contribute greatly to success or failure when adopting and implementing fisheries management tools. Catch-and-release (C&R) is one such tool where success is influenced by both variation in human factors, but also species and fishery specific characteristics. In this study, an intercept survey of 94 sea trout anglers in a C&R dominated fishery on the Swedish island of Gotland investigated motivations to release or retain catches, self-assessment of anglers’ own ability to release fish, and their rating of the importance of various factors influencing the successful outcomes of C&R. Retention of catches was most strongly motivated by situations where anglers deemed the fish unlikely to survive, however more than half of anglers acknowledged being unaware of delayed mortality in released fish. The spawning status of an individual fish was the primary motivation for release, particularly among anglers that prefer to keep at least some of their catches. The roles of water temperature, using single, and barbless hooks were scored as significantly less important than other components contributing to the success of a release. Anglers that gave a favourable rating to their ability to release sea trout also gave greater importance to various factors influencing the success of release, reported higher catch per unit effort, and released a greater proportion of their catches. These findings are discussed in the context of bridging knowledge and behavioural gaps around best practices for C&R in this fishery.

Growth analysis and sex ratio of fish species from the Ovia River, Edo State, Nigeria

This study investigated the length-weight relationships, the condition factor, and the sex ratio of Hemichromis fasciatus, Synodontis nigrita, and Tilapia zillii in the Ovia River, Edo State, Nigeria. Fish specimens were collected with the assistance of artisanal fishermen using fishing traps, cast and gill nets of various mesh sizes from February to April 2021. Taxonomical identification, morphometric measurements, and macroscopic examination of the fresh gonads were carried out. The linear regression equation was used to determine the relationship between fish length and body weight, while the condition factor and the sex ratio were analysed using standard techniques. Length-weight relationship (LWR) showed a significant (p < 0.05) correlation and the growth exponent b = 2.973, 2.340, and 2.565 for H. fasciatus, S. nigrita and T. zillii, respectively, indicated a negative allometric growth pattern. Mean condition factor values ranged from 2.34 to 5.68 and was indicative of good health condition for the fishes. Sex ratios did not differ significantly (p > 0.05) from the one male to one female distribution in H. fasciatus (1:1.11), S. nigrita (1:0.89), and T. zillii (1:0.93). The study has provided information on some aspects of the fish biology of Hemichromis fasciatus, Synodontis nigrita, and Tilapia zillii in the Ovia River, and these data are helpful tools for fisheries management and conservation of freshwater fishes.

Generation of a chromosome-level genome assembly for Pacific halibut (Hippoglossus stenolepis) and characterization of its sex-determining genomic region.

The Pacific halibut (Hippoglossus stenolepis) is a key species in the North Pacific Ocean and Bering Sea ecosystems, where it also supports important fisheries. However, the lack of genomic resources limits our understanding of evolutionary, environmental and anthropogenic forces affecting key life history characteristics of Pacific halibut and prevents the application of genomic tools in fisheries management and conservation efforts. In the present study, we report on the first generation of a high‐quality chromosome‐level assembly of the Pacific halibut genome, with an estimated size of 602 Mb, 24 chromosome‐length scaffolds that contain 99.8% of the assembly and a N50 scaffold length of 27.3 Mb. In the first application of this important resource, we conducted genome‐wide analyses of sex‐specific genetic variation by pool sequencing and characterized a potential sex‐determining region in chromosome 9 with a high density of female‐specific SNPs. Within this region, we identified the bmpr1ba gene as a potential candidate for master sex‐determining (MSD) gene. bmpr1ba is a member of the TGF‐β family that in teleosts has provided the largest number of MSD genes, including a paralogue of this gene in Atlantic herring. The genome assembly constitutes an essential resource for future studies on Pacific halibut population structure and dynamics, evolutionary history and responses to environmental and anthropogenic influences. Furthermore, the genomic location of the sex‐determining region in Pacific halibut has been identified and a putative candidate MSD gene has been proposed, providing further support for the rapid evolution of sex‐determining mechanisms in teleost fish.

Increasing spillover enhances southern California spiny lobster catch along marine reserve borders

AbstractThe conservation benefits of marine reserves are well established but their contribution to adjacent fisheries via spillover is less certain and context‐dependent. Theoretical predictions do not always match empirical evidence from individual reserves, so carefully designed studies are essential for accurately assessing spillover and its contribution to fisheries. Biomass buildup within reserves, and spillover from reserve borders, also usually takes time to develop. In 2003, a network of no‐take marine reserves was established in the Northern Channel Islands (NCI) of southern California (CA) to conserve biodiversity and to eventually enhance local fisheries through spillover of larvae, juveniles, and adults. The reserve network impacted the local CA spiny lobster (Panulirus interruptus) fishery by removing about 20% of fishing grounds in the NCI. In 2008, a collaborative fisheries research effort detected substantial lobster population increases within reserves, and an indication of the possible spillover of adult lobsters across reserve borders. To estimate whether and how much populations within reserves, and spillover from reserves, have increased through time, we repeated the sampling program 10 years later in 2018 at two of the three original reserves. Scientific trapping was conducted prior to the fishing season along a spatial gradient beginning deep within the reserves to reference sites located outside (≥2 km) of reserve borders. Results showed that legal‐sized lobster abundance in traps (catch per unit effort) increased by 125%–465% deep inside reserves, and by 223%–331% at sites near to reserve borders, and by nearly 400% just outside of reserve borders over the 10‐year period, thus indicating a substantial increase in spillover across reserve borders. A similar pattern was observed in lobster biomass caught in traps at the two reserves. This study demonstrates how spillover scales with biomass buildup and that collaborative fisheries research can be used to assess the efficacy of marine reserves as fishery management tools worldwide.

Analyses of the composite yield per recruit model CYPR14 for inferring plausible fishing mortality targets of fish in the tropics

Stocks' yield and size per recruit are widely used to provide fisheries management guidance. This study provides details for analyzing the composite (i.e. age-aggregated or stage-structured) yield per recruit (CYPR) model CYPR14, and proposes CYPR14 as a management tool for tropical fisheries. The fishing mortality rates maximizing CYPR (FCYPR) and associated with the marginal increase in CYPR (F0.1) and a target composite spawning potential ratio (CSPR;F35%CSPRorF40%CSPR) were suggested as candidate fishing mortality targets, provided assessments employ the delay-differential model underlying CYPR14. Using Monte Carlo (MC) simulations relying on growth parameters and natural mortality of Lake Tanganyika'sLates stappersiiand Lake Victoria'sLates niloticus, CYPR14 analyses involving maximum survivorship or declining survivorship were carried out to show howFCYPR,F0.1,F35%CSPR, andF40%CSPRcould be generated, given an age of knife-edge recruitment (r). Baseline MC employedr = 1 year and yielded mean annual rates ofFCYPR = 0.52,F0.1 = 0.33, andF35%CSPR = 0.51 forL. stappersiiandFCYPR = 0.23,F0.1 = 0.14, andF40%CSPR = 0.16 forL. niloticus. CYPR14 with maximum survivorship produced CYPR isopleths such that the CYPR maximized at an infiniterand finite, higherF. For CYPR14 involving a declining survivorship, the CYPR declined with increasedrand maximized with innermost closed-loop contours at lowerFand an optimal age. The CSPR isopleths from both types of CYPR14 analyses were first concave down, and the optimal age served as their inflection point. In terms of benchmarks based on the maximum sustainable yield and of proxies thereof, CYPR14 should be for its underlying delay-differential model what the age-structured pool models are for age-structured assessment models.