Transactions of the American Fisheries Society

In the late 1990s the Environmental Monitoring and Assessment Program of the U.S. Environmental Protection Agency developed a structured set of tests to evaluate and facilitate selection of metrics for indices of biotic integrity (IBIs). These IBIs were designed to be applicable across multistate regions as part of a national assessment of all U.S. waters. Here, we present additional steps in, and refinements to, that IBI development process. We used fish and amphibian assemblage data from 932 stream and river sites in 12 western U.S. states to develop IBIs for Mountains, Xeric, and Plains ecoregions. We divided 237 candidate metrics into nine metric classes representing different attributes of assemblage structure and function. For each ecoregion we sequentially eliminated metrics by testing metric range, signal‐to‐noise ratios, responsiveness to disturbance, and redundancy to select the best metric in each class. The IBIs for the Mountains and Plains each had seven metrics and the Xeric IBI had five. In the Mountains, half of the estimated stream length that could be assessed had IBI scores greater than 62 (out of 100). In the Xeric and Plains, half the stream length had scores no greater than 50 and no greater than 37, respectively. An estimated 16% of Xeric stream length had scores greater than 62 (the median for the Mountains), while 5% of Plains stream length had scores that exceeded 62. This IBI development process is less subjective and more streamlined and has more clearly defined criteria for metric selection and scoring than those used in the past, while maintaining a strong ecological foundation.

Using captive groups of Atlantic cod Gadus morhua from two Northwest Atlantic populations (western Scotian Shelf and southern Gulf of St. Lawrence), we quantified the temporal patterns and behavioral contexts of sound production during the spawning season. We found that sound production occurs most frequently during the peak of the spawning period, particularly after the onset of darkness. The rate of sound production by males in the western Scotian Shelf group was 8.4 times greater on average than that of the southern Gulf of St. Lawrence group, and this corresponded to differences in the mass of the sound‐producing musculature. Based on behavioral observations during daylight hours, we found that sounds were associated with both courtship behavior and agonistic displays. Although sounds were produced on only 14.5% of the occasions in which a male and female swam together in a “ventral mount,” limited data suggest that ventral mounts accompanied by sound were more likely to lead to spawning. While almost all sounds produced by Atlantic cod in our study matched the short “grunt” type previously documented for this species, we report evidence for another sound, described as a “hum,” which occurs during the ventral mount immediately before gamete release. We hypothesize that sound production is related to competition among males for access to females and may help synchronize gamete release, underscoring the potential importance of sound production to Atlantic cod spawning behavior.

Red snapper Lutjanus campechanus (N = 54) were tagged and tracked on 12 artificial reefs in the northeastern Gulf of Mexico. Fish were surgically implanted with ultrasonic transmitters and monitored with Vemco remote receivers and Sonotronics surface receivers from August 2000 to 2004. Four fish were manually tracked from the surface overnight, and their positions were recorded every hour for either 9 or 16 h. The total length of fish tagged was 589 ± 14 mm (mean ± SE). The number of detections by the remote receivers was 290,340 ± 44,696. By the end of this study, 5 fish were still being tracked, 8 fish had been lost immediately after tagging, 15 fish had been caught by fishers, and 26 fish had been lost after extended tracking. Red snapper were resident on artificial reefs for 218 ± 28 d, and residence time ranged from 1 to 595 d. We estimated that most (67%) of the tagged red snapper showed long‐term residence (117–595 d), 13% were resident for 8–91 d, and 20% left the tagging site soon after release (<4 d). Fish were resident on the same artificial reef over all seasons (winter, spring, summer, and fall), and no seasonal changes in proximity to the reef were detected. Red snapper left the receiver range (1.6 km) for short time periods; for example, fish 25 left the reef 285 times for 1–4 h over a 335‐d period. However, all fish spent most of their time (98%) within the receiver range. We detected diel changes in proximity to the reefs (N = 8), but patterns varied. In this study, red snapper showed high site fidelity over long time periods, which suggested that artificial reefs provided suitable habitat for red snapper in the northeastern Gulf of Mexico.

The Alverson and Carney (AC) model for estimating the instantaneous rate of natural mortality (M) was reformulated to include β andt₀parameters. The revised Zhang and Megrey (ZM) model could be used for the estimation ofMinstead of the AC model since von Bertalanffy and allometric growth parameters are readily available for most exploited fish stocks. It was determined from the new formulation that the ratios of the age at maximum biomass (t_mb) to the maximum age (t_max) for pelagic and demersal species were significantly different from 0.38, the value originally proposed by Alverson and Carney. The ratios for these two ecological groups were 0.302 and 0.440, respectively, and were significantly different. We examined the sensitivity and bias inMfrom the new formulation relative to those from the AC model, which assumed that β = 3.0 andt₀= 0. Estimates ofMfrom the AC model are most sensitive to the assumption that growth starts att₀= 0 when growth rates are high as well as to the β andt_mbassumptions. The performance of the revised ZM model was evaluated by comparing calculatedMvalues from the two models based on a paired‐samplet‐test. The results of the two statistical analyses showed that the ZM model produced values ofMcloser to published estimates than did the AC model. Thus, the ratiot_mb/t_maxfor specific ecological groups should be used rather than Alverson and Carney's constant 0.38. Analyses of exploited stock dynamics might be conducted using the possible range ofMinstead of the constant value. The range could be estimated from the ZM model using the mean ratiot_mb/t_max± SD to get thet_mbfor each subgroup or by explicit variance calculations.

Red Snapper Lutjanus campechanus are generally associated with artificial reef habitats in the northern Gulf of Mexico, but whether this association results in fish production is still controversial. Information on fine‐scale habitat use patterns would be helpful in evaluating this. Little is known about the fine‐scale movement patterns of Red Snapper around artificial reefs. The present study examined fine‐scale (∼1‐m accuracy) movements of Red Snapper with the Vemco VR2W Positioning System. This system enabled continuous monitoring of tagged fish from 100 to 694 d. Locations of individual fish were recorded approximately every 10 min and totaled over 1.9 million accurate locations of Red Snapper from August 2010 through May 2012. Red Snapper showed close association with the reef structure (mean ± SD distance = 26.3 ± 35.4 m) but differential habitat use in relation to both diel and seasonal periods. Home range areas (95% kernel density estimates [KDE]) were significantly larger during day than night periods and showed the lowest area use at dawn and dusk. Monthly home ranges (95% KDE) and core areas (50% KDE) were significantly larger in spring, summer, and fall than in winter and were significantly correlated with water temperature, suggesting colder winter temperatures reduced Red Snapper movement. Home range area was significantly correlated with fish size (407–590 mm standard length), and the fish in this study showed the highest site fidelity (88% still present after >10 months) of any Red Snapper in other previous studies. Red Snapper also showed use of multiple reefs within the monitoring area, as home ranges (95% KDE) showed a second peak around other artificial reefs. The high site fidelity, long‐term use, and concentrated use of multiple artificial reefs confirm the importance of structured habitat for Red Snapper.

Received September 1, 2013; accepted February 27, 2014

Diets of red snapper Lutjanus campechanus were compared among four diel feeding periods (dawn, day, dusk, and night) and among three standard length size‐classes: small (200–299 mm), medium (300–399 mm), and large (400–499 mm). Fish were collected from August through October 2000 in the north‐central Gulf of Mexico. A total of 432 stomachs were examined, of which 164 (37%) contained prey. Size‐class influenced diets; diets of small red snapper were dominated by fish, those of medium red snapper by fish and tunicates, and those of large red snapper by crabs and fish. Red snapper fed on prey from several different habitats. Small red snapper fed mostly on reef and sand prey types; medium red snapper fed on similar portions of reef, sand, and mixed prey types; and large red snapper fed on mixed prey types. Adjusting for fish size, mean gut fullness was significantly lower for the dusk than for the day period. Fish were the most important prey for all periods. The second most important prey group changed with period: stomatopods for dawn, tunicates for day, and crabs for dusk and night periods. Prey habitat type also varied over periods. Sand prey type dominated dawn and dusk periods, whereas reef prey type dominated day and night periods. We used multidimensional scaling analysis to compare the relative influence of diel period to size‐class on red snapper diets. This analysis suggested that fish size‐class had a greater influence on red snapper diet than did period. However, with size effects removed, red snapper still showed significant diet shifts with periods.

Dams created by North American beavers Castor canadensis (hereafter, “beavers”) have numerous effects on stream habitat use by trout. Many of these changes to the stream are seen as positive, and many stream restoration projects seek either to reintroduce beavers or to mimic the habitat that they create. The extent to which beaver dams act as movement barriers to salmonids and whether successful dam passage differs among species are topics of frequent speculation and warrant further research. We investigated beaver dam passage by three trout species in two northern Utah streams. We captured 1,375 trout above and below 21 beaver dams and fitted them with PIT tags to establish whether fish passed the dams and to identify downstream and upstream passage; 187 individual trout were observed to make 481 passes of the 21 beaver dams. Native Bonneville Cutthroat Trout Oncorhynchus clarkii utah passed dams more frequently than nonnative Brown Trout Salmo trutta and nonnative Brook Trout Salvelinus fontinalis. We determined that spawn timing affected seasonal changes in dam passage for each species. Physical characteristics of dams, such as height and upstream location, affected the passage of each species. Movement behaviors of each trout species were also evaluated to help explain the observed patterns of dam passage. Our results suggest that beaver dams are not acting as movement barriers for Bonneville Cutthroat Trout or Brook Trout but may be impeding the movements of invasive Brown Trout.

Sex ratio, size at maturity, reproductive periodicity, ovarian development pattern, and spawning ground data for red snapper Lutjanus campechanus from the southern Gulf of Mexico were analyzed to understand this species' reproductive biology throughout its geographical distribution. Red snapper were sampled in 1999 and 2000 from commercial fishery catches taken on Campeche Bank at depths ranging from 43 to 130 m. Overall sex ratio (male: female) and sex ratios by size‐class did not differ significantly from a 1:1 ratio. First maturity was at a slightly smaller size in males (24.2 cm total length [TL]) than in females (28.3 cm TL), and maximum length percentages at first maturity were 28% for males and 34% for females. The length at which maturity was attained in 50% of females (L50) was 31.4 cm TL. The Campeche Bank red snapper stock had a protracted spawning period from February to November, with a spawning peak occurring in early fall. Vitellogenic oocytes were continually recruited from previtellogenic oocytes during the entire spawning season, with no gap between each oocyte development stage. This means that red snapper ovaries are asynchronous and that the species can be considered a heterochronal (batch) spawner with indeterminate annual fecundity. Females in spawning condition were collected from both the northeastern and northwestern areas of Campeche Bank, near submerged or emergent coral reef structures, and at depths between 48 and 117 m. These results generally agreed with those for red snapper stocks in others regions of the Gulf of Mexico and the Atlantic Ocean off the southeastern United States. However, reproductive periodicity in the Campeche Bank red snapper stock apparently displayed more of an insular pattern of extended spawning in comparison with the typical continental pattern of restricted spawning reported for other regions. The latitudinal differences observed in red snapper spawning seasons could also reflect a latitudinal gradient in the intensity of seasonal environmental constraints.