Sex and reproductive maturity of Atlantic and shortnose sturgeon were determined by visual examination of the gonads using laparoscopy, and were validated by histological examination of gonadal biopsies. Surgical anesthesia was induced in all fish with 250 mg L )1 tricaine methanesulfonate (MS-222) and maintained throughout procedures with 85 mg L )1 MS-222 on a mobile surgical cart. A pair of Ternamian EndoTip cannulae installed through the ventral body wall in each fish, allowed access for a 5-mm rigid laparoscope and biopsy forceps. Video endocamera use with the laparoscope, following air insufflation of the coelom, provided detailed, high quality imagery to aspirate the swim bladder, examine the gonad and collect biopsies without inducing iatrogenic trauma. Germinal tissue of all immature males, 25% of immature female shortnose sturgeon and 45% of immature female Atlantic sturgeon were concealed by fat preventing sex determination by visual assessment. Morphological features of gonads were used to determine sex in all remaining fish and were 100% in concordance with histological findings. Relative amount of gonadal fat; gonad size and color; presence of testicular lobes or ovarian lamellae; and color, size and density of oocytes were useful in determining reproductive stage. Gonad morphology of each reproductive stage was similar in Atlantic and shortnose sturgeon. All captive Atlantic sturgeon survived laparoscopy, gained weight at the same rate as unexamined fish and scars from incisions were no longer evident 9-12 months after surgery. Laparoscopic procedures presented here offer a safe and highly reliable way to determine sex and reproductive status for Atlantic and shortnose sturgeon.

Background The imperiled status of Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus), a large, long‐lived, anadromous fish found along the Atlantic coast of North America, has prompted efforts at captive propagation for research and stock enhancement. Objective The purpose of this study was to establish hematology and plasma chemistry reference intervals of captive Atlantic sturgeon maintained under different culture conditions. Methods Blood specimens were collected from a total of 119 fish at 3 hatcheries: Lamar, PA (n = 36, ages 10–14 years); Chalk Point, MD (n = 40, siblings of Lamar); and Horn Point, Cambridge, MD (n = 43, mixed population from Chesapeake Bay). Reference intervals (using robust techniques), median, mean, and standard deviations were determined for WBC, RBC, thrombocytes, PCV, HGB, MCV, MCH, MCHC, and absolute counts for lymphocytes (L), neutrophils (N), monocytes, and eosinophils. Chemistry analytes included concentrations of total proteins, albumin, glucose, urea, calcium, phosphate, sodium, potassium, chloride, and globulins, AST, CK, and LDH activities, and osmolality. Results Mean concentrations of total proteins, albumin, and glucose were at or below the analytic range. Statistical comparisons showed significant differences among hatcheries for each remaining plasma chemistry analyte and for PCV, RBC, MCHC, MCH, eosinophil and monocyte counts, and N:L ratio throughout all 3 groups. Therefore, reference intervals were calculated separately for each population. Conclusions Reference intervals for fish maintained under differing conditions should be established per population.

Preserving freshly collected blood in 10% formalin is a reliable method to maintain cell morphology for manual counts for up to 1 month post collection. This is especially useful for field studies, where laboratory access is limited. Further evaluation is needed to determine the clinical usefulness of the manual RBC count in fish.

Summary Non‐lethal sampling techniques were used to document the reproductive structure of the shortnose sturgeon (Acipenser brevirostrum) population at a fish aggregation site (near Bordentown, New Jersey) in the Delaware River. A total of 68 fish were captured using gill nets (100 × 1.8 m, 12.7 or 15.2 cm mesh) and examined laparoscopically in May–June, and 61 additional fish captured and examined in November during 2006–2011. Six stages of reproductive development were identified in females and five stages were identified in males, encompassing differentiation through maturity in both sexes. Fish captured in the spring were predominantly immature with a higher proportion of females (1 : 1.2 M : F sex ratio), while mature males predominated in the autumn (5.7 : 1 M : F), indicating that the Bordentown area serves as an overwintering/pre‐spawn aggregation site. Three distinct forms of intersex were noted in gonads of 11.6% of fish examined: ovo‐testis, consisting of scattered spermatic cysts in predominantly immature ovary (3.9%); testis‐ova, consisting of ovarian lamellae projecting from a predominantly immature testes (4.7%); and zonal distribution, consisting of multiple, nearly‐homogenous pockets of either testicular or ovarian tissues along the gonad (3%). The hormone profile in fish with ovo‐testis was similar to that of immature males, while the hormone profile in fish with testis‐ova was similar to that of immature females. The relatively high prevalence of intersex raises concerns regarding potential reproductive effects and long‐term impacts on shortnose sturgeon in the Delaware River.

Summary The effects of gender, maturity, intersex condition and annual and seasonal variability were studied on hematology and plasma chemistry of wild shortnose sturgeon Acipenser brevirostrum from the Delaware River. A total of 68 fish were captured by gill net and examined in May‐June, and 61 additional fish were captured and examined in November during 2006–2011. Total leukocyte counts (WBC), leukogram, PCV and the plasmatic concentrations of 13 biochemical analytes were measured from these fish using standard clinical methods. Season and gender had no effect on hematologic indices, but PCV was inversely related to maturity of fish (robust intervals: 27–40% in immature fish, 21–36% in mature fish). Significant annual variation was detected in eosinophil (annual range in robust interval: 0–1176 lower limit, 670–7882 upper limit) and monocyte (0–210 lower limit, 560–1980 upper limit) counts (cells μl−1). The lower limit of the robust interval varied annually by as much as 6% for sodium and 12% for chloride, while the upper limit of the robust interval varied annually by as much as 8% for sodium and 15% for chloride. Seasonal differences in mean sodium and chloride (6–7% higher in autumn) and proteins (5–13% higher in autumn) may reflect environmentally induced changes in osmoregulation, while aspartate aminotransferase was 38–55% higher in the spring. In females, calcium and total protein were highest in mature fish (robust intervals: 10.5–22.1 mg dl−1 Ca2+, 4.1–6.9 g dl−1 TP) compared to immature (7.3–16.9 mg dl−1 Ca2+, 2.8–5.2 g dl−1 TP) and developing fish (7.8–18.9 mg dl−1 Ca2+, 3.2–5.6 g dl−1 TP), indicating changes associated with vitellogenesis. Glucose was significantly higher in females (robust interval: 23–167 mg dl−1) than males (35–138 mg dl−1), possibly indicating gender‐based differences in energetic requirements. Intersex condition was associated with lowered glucose, potassium and creatinine phosphokinase. Reference intervals reported here are useful for evaluating the health and physiological condition of shortnose sturgeon.