Michael J. Andres

Sheepshead (Archosargus probatocephalus) are an ecologically and economically important estuarine species in the northern Gulf of Mexico; however, fine-scale movement and survival patterns remain poorly understood. Therefore, we used acoustic telemetry to monitor 61 adult Sheepshead in the Mississippi Sound to evaluate apparent survival, residency, and movement among estuarine sub-systems. A size-based maturity ogive indicated that nearly all tagged individuals were reproductively-capable at the time of tagging. Apparent survival differed by location, with St. Louis Bay-tagged individuals displaying lower survival than those from the Pascagoula River Estuary, although first-year survival did not differ. Residency analyses revealed that 50 percent of tagged adults remained within their capture sub-systems year-round, while the other half left during spawning months. Movement network analyses identified sub-system-specific hubs that facilitate regional connectivity, while individual-level variation revealed both mobile and resident fish. Environmental covariates, including salinity and sea surface temperature, significantly influenced the probability of departure from the capture sub-system. Overall, these results reveal Sheepshead exhibit spatially variable survival, diverse movement strategies, and reproductive-related movement behaviors.

Gulf sturgeon are federally listed as “threatened” and are native to seven rivers along the northern Gulf of Mexico. Populations natal to the Pascagoula River have one verified spawning reach in the lower Bouie River, near Hattiesburg, MS. This reach is modified by four aggregate mining areas, referred to as pits. Researchers observed post-spawn Gulf sturgeon over-summering in pits rather than migrating to downstream holding areas in the Pascagoula River. We leverage acoustic telemetry and environmental data to assess drivers of arrival and departure from the Bouie River, describe vertical stratification in the water column in pits, and compare pit temperatures to those in holding areas. Generalized mixed linear modeling demonstrated that arrival was associated with lower discharge rates, whereas departure was associated with higher surface water temperatures and greater daily temperature extremes. Sturgeon had varying occupancy rates in pits, with four over-summering events over 3 years. Stratification formed in the pits in May and persisted through October, with bottom and middle strata exhibiting cooler temperatures than holding habitats. Cooler bottom temperatures indicate potential for thermal refuge in the pits. However, persistent stratification leads to low dissolved oxygen in bottom waters, warranting further research into the environmental stressors of this system.

The current study examined 93 Swordfish, Xiphias gladius, (64 females, 27 males, 2 unknown) ranging in size from 77.6–246.3 cm lower jaw fork length (LJFL) from the northern Gulf of Mexico (GOM). Samples were collected between March and August in 2005–2007, 2017–2019 and 2021. Age estimates of 51 Swordfish resulted in a maximum observed age of 11 years (205.0 cm LJFL) and 7 years (190.4 cm LJFL) for females and males, respectively. Observed and back—calculated length—at—age data were fitted to 4 growth models (2— and 3— parameter von Bertalanffy, Gompertz, and logistic). The 2—parameter von Bertalanffy was the model that best fit the data (Linf = 210.2 cm LJFL, k = 0.25). Histological examination of gonadal tissue from 91 fish indicated that females reached 50% and 95% physiological maturity at 116 ± 6 cm LJFL and 143 ± 8 cm LJFL, respectively, corresponding to ages 2—3 years. All males >82 cm LJFL were physiologically sexually mature. Only 10% of females were reproductively active, with spawning capable females captured in June. Reproductively active females exhibited asynchronous oocyte development indicating batch spawning. Most males (96%) were spawning capable from April–August. Philometra sp. infection was found in all ovaries examined (n = 16) but with low abundance (2.25 ± 0.42); male philometrids were more prevalent than females (91.7% and 66.7%, respectively). Swordfish in the northern GOM appear to achieve sexual maturity at a younger age, grow faster, and have shorter theoretical longevity than previous reports from other regions world—wide.

This paper aims to highlight the new research and significant advances in our understanding of links between coastal habitat quality/quantity/diversity and the diversity of fisheries species and other mobile aquatic species (hereafter nekton) that use them within coastal landscapes. This topic is quite diverse owing to the myriad of habitat types found in coastal marine waters and the variety of life history strategies fisheries species and nekton use in these environments. Thus, we focus our review on five selective but relevant topics, habitat templates, essential fish habitat, habitat mosaics/habitat connectivity, transitory/ephemeral habitat, and the emerging/maturing approaches to the study of fish-habitat systems as a roadmap to its development. We have highlighted selected important contributions in the progress made on each topic to better identify and quantify landscape scale interactions between living biota and structured habitats set within a dynamic landscape.

Species of Argulus (Branchiura Thorell, 1864) are common ectoparasites of freshwater, estuarine, and marine fishes. Argulid identification and taxonomy is often confusing because many species are reported to parasitize multiple host species, have similar morphological characters, and come from various salinity regimes. Gulf sturgeon is an anadromous fish natal to drainages in the north-central Gulf of Mexico, and as with many endangered species, has a poorly documented parasite community. During Gulf sturgeon tagging and monitoring studies (2016–2019) in the Pascagoula River, MS, USA, species of Argulus were collected from Gulf sturgeon as well as other incidentally captured fishes. Argulus flavescens Wilson, 1916 was found on Gulf sturgeon and flathead catfish, Argulus americanus Wilson, 1902 on bowfin, and Argulus bicolor Bere, 1936 on Atlantic stingray. We provide morphological details and measurements for these species as well as the first confirmed 28S rDNA molecular data. Argulus flavescens was more abundant and prevalent on larger Gulf sturgeon and on sturgeon captured in freshwater rather than estuarine habitats. Our results indicate that A. flacescens may not tolerate estuarine salinities and that the anadromous life-history pattern of Gulf sturgeon could help rid them of A. flavescens when they emigrate from their riverine habitats.

Multimodel inference of length‐at‐age and tag–recapture data was used to estimate growth for western population segment (WPS; populations natal to the Pearl River, Louisiana, and the Pascagoula River, Mississippi) Gulf Sturgeon Acipenser oxyrinchus desotoi. Four candidate growth models were fitted to the length‐at‐age data (n = 174): a three‐parameter von Bertalanffy growth function (VBGF), a two‐parameter VBGF, a power model, and a Gompertz model. Model support for each data set was estimated using Akaike's information criterion. The Gompertz model provided the best fit to our length‐at‐age data and had the lowest mean asymptotic maximum length (L_∞). Mean estimated growth parameters for WPS Gulf Sturgeon were similar to those estimated for eastern population segment Gulf Sturgeon, but some of the mean parameter estimates fell outside of our 95% confidence intervals. Three growth curves were also fitted to tag–recapture data (n = 116): a reformulated two‐parameter VBGF, the Francis () GROTAG model, and a reparametrized Gompertz model. The GROTAG model provided the best fit to our data; all three models had lower mean estimates for L_∞ compared with parameter estimates based on length at age but had similar mean growth coefficients. We also compared the observed growth of 47 individuals with their predicted growth based on parameter estimates of the Gompertz length‐at‐age model and their age at tagging. We found that observed growth was generally less than what was predicted for juveniles and adults. For adults, we attribute this to the inaccuracies associated with age estimation for older individuals, which suggests that a tag–recapture approach might be the most appropriate method of modeling Gulf Sturgeon growth. Our study (1) demonstrates the importance of fitting multiple models to estimate growth, (2) will enable more accurate growth comparisons for Gulf Sturgeon across their range, and (3) represents the most robust length‐at‐age and tag–recapture data set for WPS Gulf Sturgeon.

Three species of Isorchis Durio and Manter, 1969 are described from Australian waters. Isorchis megas sp. nov. is described from the spotbanded scat, Selenotoca multifasciata (Richardson), off Western Australia (WA) and Northern Territory (NT); Isorchis currani sp. nov. is described from S. multifasciata off NT; and Isorchis anomalus sp. nov. is described from the milkfish, Chanos chanos Forsskål, off WA. Isorchis megas sp. nov. can be differentiated from the other species of Isorchis by possessing a single, large egg that is greater than 20% of the body length; having a shorter body (the largest specimen is less than 500 μm); and utilizing a scatophagid rather than a chanid host. Isorchis currani sp. nov. can be differentiated from species of Isorchis other than I. megas sp. nov. by utilizing a scatophagid rather than a chanid host; it is differentiated from I. megas sp. nov. in having eggs that are 11-15% of the body length. Isorchis anomalus sp. nov. can be differentiated from all other species of Isorchis in possessing an irregular shaped genital pore rather than one that is circular to oblong. A Bayesian inference analysis of partial 28S rDNA sequences of the three new species of Isorchis and 30 other haploporoids revealed 1) the monophyly of the Atractotrematidae Yamaguti, 1939, 2) the two species of Isorchis infecting S. multifasciata were each other's closest relative, and 3) that Isorchis was most closely related to Pseudomegasolena Machida and Komiya, 1976 rather than Atractotrema Goto and Ozaki, 1929 although sequence data are not yet available for a member of Pseudisorchis Ahmad, 1985.

Polychlorinated dibenzo-p-dioxins and dibenzofurans (dioxins) are persistent contaminants that bioaccumulate and pose serious risks to humans. The primary objective of this study was to determine the history and mechanisms of dioxin accumulation in sediments of the Houston Ship Channel (HSC) using analytical data on natural and anthropogenic radionuclides (⁷Be, ¹³⁷Cs, and ²¹⁰Pb) and dioxins. Results showed that present-day sedimentary dioxin accumulation rates are orders of magnitude higher than atmospheric inputs to the HSC. Most stations showed dioxin peaks in the near surface, indicating continuing inputs despite federal regulations. Stations with high dioxin inventories reflect accentuated accumulation in the HSC as one moves west toward Houston, at the confluence of the HSC and the San Jacinto River and upstream in the San Jacinto River. These results indicate that a significant quantity of dioxins continues to be released into the environment here or that sedimentary storage and release of previously supplied dioxins is significant, or both. The results support the interpretation that the HSC is influenced by episodic sediment resuspension, erosion and lateral transport processes driven by tides, wind, shipping, and dredging, which can cause intermittently high accumulations of dioxins, and underscores the need for additional research on the roles of sedimentary processes in organic contaminant bioavailability.