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Developing‐world shark fisheries are typically not assessed or actively managed for sustainability; one fundamental obstacle is the lack of species and size‐composition catch data. We tested and implemented a new and potentially widely applicable approach for collecting these data: mandatory submission of low‐value secondary fins (anal fins) from landed sharks by fishers and use of the fins to reconstruct catch species and size. Visual and low‐cost genetic identification were used to determine species composition, and linear regression was applied to total length and anal fin base length for catch‐size reconstruction. We tested the feasibility of this approach in Belize, first in a local proof‐of‐concept study and then scaling it up to the national level for the 2017–2018 shark‐fishing season (1,786 fins analyzed). Sixteen species occurred in this fishery. The most common were the Caribbean reef (Carcharhinus perezi), blacktip (C. limbatus), sharpnose (Atlantic [Rhizoprionodon terraenovae] and Caribbean [R. porosus] considered as a group), and bonnethead (Sphyrnacf. tiburo). Sharpnose and bonnethead sharks were landed primarily above size at maturity, whereas Caribbean reef and blacktip sharks were primarily landed below size at maturity. Our approach proved effective in obtaining critical data for managing the shark fishery, and we suggest the tools developed as part of this program could be exported to other nations in this region and applied almost immediately if there were means to communicate with fishers and incentivize them to provide anal fins. Outside the tropical Western Atlantic, we recommend further investigation of the feasibility of sampling of secondary fins, including considerations of time, effort, and cost of species identification from these fins, what secondary fin type to use, and the means with which to communicate with fishers and incentivize participation. This program could be a model for collecting urgently needed data for developing‐world shark fisheries globally. Article impact statement: Shark fins collected from fishers yield data critical to shark fisheries management in developing nations. [ABSTRACT FROM AUTHOR]

Stock enhancement is an increasingly popular fisheries management strategy in which high mortality of early life history stages is circumvented by rearing juveniles in controlled or semi-controlled conditions. While the success of such programs is generally measured by the number of stocked individuals or individuals recruiting to the wild populations, an important consideration is minimizing impacts to the genetic diversity of wild populations by maximizing the number of breeders contributing to stocked progeny. The contribution of individual breeders is impacted both by variance in spawning success among adults and variance in mortality among families during grow-out. To disentangle the effects that these sources of variance have on parental contribution, red drum broodfish participating in three spawning events at the TWPD Marine Development Center were genotyped at several thousand SNP-containing loci along with their progeny. Progeny were sampled at three time points; shortly after introduction to grow-out ponds (T1), approximately midway through grow-out (T2), and as fingerlings during harvesting to be stocked in bays (T3). Using composite genotypes, progeny were assigned to parents to determine the reproductive success of individual broodfish at T1, T2, and T3 and to identify changes in the effective number of breeders (N b) during rearing in grow-out ponds. Relationships between reproductive success and broodfish-specific parameters, including age and condition when introduced to the hatchery, time spent in the hatchery, and estimated age at spawning were assessed. Finally, associations between components of genomic variation in progeny from each sampling period and environmental parameters including salinity, pH, temperature, and dissolved oxygen present in the grow-out ponds, were identified. The results indicate that initial variance in reproductive success, including the failure of some individuals to spawn successfully, has the greatest impact on N b. Mortality during growth had a relatively small impact on N b and, in some cases, led to increases in N b. Further, both family and environmental conditions in the outdoor rearing ponds significantly shaped the genetic diversity of stocked yearlings. Overall, these findings indicate that outdoor rearing in a semi-controlled environment exposes progeny to a range of environmental conditions across the season, which appears to play a role in maintaining and sometimes increasing N b. • Reproductive success of broodstock is highly variable, reducing effective number of breeders • No. of successful reproducers has greatest impact on genetic diversity of stocked progeny • Outdoor rearing exposes yearlings to range of natural environmental conditions • Environmental conditions in outdoor ponds maintains genetic diversity of stocked progeny [ABSTRACT FROM AUTHOR]

In contrast to freshwater fish it is presumed that marine fish are unlikely to spawn with close relatives due to the dilution effect of large breeding populations and their propensity for movement and reproductive mixing. Inbreeding is therefore not typically a focal concern of marine fish management. We measured the effective number of breeders in 6 New York estuaries for winter flounder (Pseudopleuronectes americanus), a formerly abundant fish, using 11 microsatellite markers (6–56 alleles per locus). The effective number of breeders for 1–2 years was remarkably small, with point estimates ranging from 65–289 individuals. Excess homozygosity was detected at 10 loci in all bays (FIS = 0.169–0.283) and individuals exhibited high average internal relatedness (IR; mean = 0.226). These both indicate that inbreeding is very common in all bays, after testing for and ruling out alternative explanations such as technical and sampling artifacts. This study demonstrates that even historically common marine fish can be prone to inbreeding, a factor that should be considered in fisheries management and conservation plans. [ABSTRACT FROM AUTHOR]