Biology subjects

Hyman, A. C.

Publications and source records attributed to Hyman, A. C..

4 recordsLinked to original sources

bioRxiv2026

Integrating conventional tagging and acoustic telemetry improves estimates of post-release survival in a highly targeted reef fish

Accurate estimation of post-release survival is fundamental to fisheries stock assessment and effective management. Conventional tag-return studies and acoustic telemetry are commonly used to estimate this probability, yet each approach has limitations when applied independently. Using gag (Mycteroperca microlepis) as a case study, we integrated data from a large-scale conventional tagging program and an acoustic telemetry experiment within a discrete-time statistical modeling framework that links relative recapture risk with telemetry-derived fate. This approach enabled estimation of post-release survival across a broad gradient of capture depths representative of recreational fishing conditions. Estimated survival was high in shallow waters ({approx}97%) but declined with increasing capture depth, consistent with depth-related barotrauma. Applying model predictions to depth distributions from the recreational fishery yielded annual and monthly post-release survival probabilities. Annual estimates were consistent with values assumed in recent stock assessments, while monthly values highlighted seasonal patterns potentially relevant for management. This integrated framework advances post-release survival estimation by combining the extensive sample sizes and environmental coverage characteristic of conventional tagging data with the direct fate observations provided by acoustic telemetry, and offers a transferable approach for other highly targeted fisheries.

ecology↗

bioRxiv2025

Survival across habitats and sizes explains ontogenetic habitat shifts in juvenile blue crabs

Juvenile organisms often shift habitat usage during ontogeny to balance changing needs for growth and refuge, yet fine-scale habitat shifts within narrow size classes remain understudied. We conducted a manipulative tethering experiment to quantify size-specific survival of juvenile blue crabs across three habitats - seagrass meadows (seagrass), salt marsh edge (SME), and unvegetated sand flats (sand) - in the York River, Chesapeake Bay, USA. We also accounted for spatial orientation, seasonality, and turbidity. Results were analyzed using Bayesian hierarchical logistic regression models. Survival varied with crab size, habitat, and time of year, with an interaction between size and habitat. Smaller juveniles had the highest survival in seagrass, but survival increased more rapidly with size in SME and sand habitats. By 33 mm carapace width (CW), relative survival rates in seagrass and SME were statistically indistinguishable. Meanwhile, survival in sand approached that of seagrass at approximately 45 mm CW. When considered alongside previous growth rate studies, these results suggest that seagrass offers a growth-survival advantage for crabs < 15 - 20 mm CW, while salt marsh and sand habitats become increasingly favorable for larger juveniles due to comparable survival and faster growth. Consequently, even across a relatively small size range of the juvenile phase, size-specific patterns in survival differ substantially across structured and unstructured habitats. Our findings align with observed patterns of size-specific habitat use and underscore the complementary nursery roles of seagrass and salt marshes, reinforcing their joint importance in habitat restoration and conservation strategies for juvenile blue crabs.

ecology↗

bioRxiv2023

Model-based evaluation of critical nursery habitats for juvenile blue crabs through ontogeny: abundance and survival in seagrass, salt marsh, and unstructured bottom

Nursery habitats confer higher food availability and reduced predation risk, thereby contributing disproportionately more individuals per unit area to the population compared with other habitats. Nursery status is inferred through evaluation of four metrics: density, growth, survival, and linkage between juveniles and adults. Moreover, organisms commonly use multiple habitats as nurseries throughout ontogeny to satisfy shifting resource requirements. To this end, we conducted manipulative and mensurative field experiments to evaluate two nursery metrics, abundance and survival, for juvenile blue crabs across multiple size classes and habitats, including structurally complex habitats -- seagrass meadows and salt marshes -- and unstructured habitat (sand flats) in the York River, Chesapeake Bay. We also considered effects of site-specific spatial orientation within the York River, seasonality, physicochemical variables, and postlarval influx. Our results showed that abundance was higher in both seagrass meadows and salt marshes relative to unstructured sand, and positively associated with turbidity and post-larval abundance. Notably, seagrass habitats harbored the highest abundances of small ([≤] 15 mm carapace width) juveniles, whereas salt marsh edge harbored the highest abundance of medium (16-30 mm carapace width) and large (31- 60 mm carapace width) juveniles. Moreover, survival was positively associated with juvenile size and structurally complex habitats relative to unvegetated controls. Seasonally, survival peaked in April, reached a seasonal minimum in August, and increased throughout fall. Finally, habitat-specific survival was dependent on spatial position: survival was elevated at upriver salt marsh and unstructured sand habitats compared to downriver counterparts. In nursery habitats of marine species, evaluation of survival, growth, abundance and ontogenetic habitat shifts has typically focused on relatively broad size ranges through the juvenile phase. Yet, ontogenetic shifts in habitat use may occur within much narrower size ranges, which has not been well studied and which is critical to the conservation and restoration of nursery habitats. We found that habitat-specific utilization rates differed by juvenile size class over a surprisingly narrow range of size, and were related to (1) the structural and biological characteristics of the nominal nursery habitats, (2) spatial gradients of environmental variables within the tributary, and (3) the likely trade-offs between growth and survival through ontogeny. Taken together, abundance and survival results indicate that seagrass meadows are key nurseries primarily for early-stage juveniles, whereas salt marshes are an intermediate nursery habitat for larger individuals to maximize growth-to-mortality ratios. Our results underscore the need to consider both habitats as critical nurseries for juvenile blue crabs throughout ontogeny.

ecology↗

bioRxiv2023

Assessment of treatment-specific tethering survival bias for the juvenile blue crab Callinectes sapidus in a simulated salt marsh

The blue crab (Callinectes sapidus) is ecologically and economically important in Chesapeake Bay. Nursery habitats, such as seagrass beds, disproportionately contribute individuals to the adult segment of populations. Spartina alterniflora salt marshes are intertidal nursery habitats which may serve as a refuge from predation for juvenile blue crabs. However, the effects of various characteristics of salt marshes on nursery metrics, such as survival, have not been quantified. Comparisons of juvenile survival between salt marshes and other habitats often employ tethering to assess survival. Although experimental bias when tethering juvenile prey is well recognized, the potential for habitat-specific bias in salt marshes has not been experimentally tested. Using mesocosm experiments, we tested if tethering in simulated salt marsh habitats produces a habitat-specific bias. Juvenile crabs were randomly tethered and un-tethered in mesocosms at varying simulated shoot densities. Tethering reduced survival, and its effect was not habitat specific, irrespective of shoot density, as evidenced by a non-significant interaction effect between tethering treatment and habitat. Thus, tethering juvenile blue crabs in salt marsh habitat did not produce treatment-specific bias relative to unvegetated habitat across a range of shoot densities and survival of tethered and untethered crabs was positively related to shoot density. These findings indicate that tethering is a useful method for assessing survival in salt marshes, as with other nursery habitats including seagrass beds, algae and unstructured sand.

ecology↗