Management policies related to catch‐and‐release (CR) angling of smallmouth bass Micropterus dolomieu vary widely across the geographic distribution of the species. Some jurisdictions, principally in the northern latitudes, prohibit or limit angling efforts that target nesting male smallmouth bass, whereas angling during the nesting period is generally unregulated in southern jurisdictions. Existing studies of individual‐level angling impacts on nesting smallmouth bass have primarily been conducted in the north; thus, the extent to which these findings are relevant to other regions is unknown. In the current study, we sought to systematically evaluate the rates of nest abandonment by nesting smallmouth bass subjected to common angling practices (CR treatment: Brief angling and no exposure to air; air exposure [AE] treatment: Exhaustive angling and 3 min of AE) and tournament practices (simulated tournament [ST] treatment: Exhaustive angling, 2 h of live‐well retention, and 3 min of AE prior to release) across a latitudinal gradient encompassing virtually the entire south‐north range of smallmouth bass (i.e., southern Missouri [MO], southern Ontario [SON], and northern Ontario [NON]) and compared these treatment groups with nonangled controls. We also quantified the extent to which physiological disturbance associated with angling varied across latitudes (peripheral populations [MO and NON] versus the intermediate‐latitude population [SON]). Whole‐blood lactate and glucose levels were highest in fish subjected to ST conditions, indicating increased stress; this pattern was conserved across all latitudes (although there was some evidence of intraspecific variation in stress response). Additionally, the pattern of brood abandonment was similar among fish at all three latitudes; ST fish exhibited the highest rates of nest abandonment (MO: Control = 9.1%, CR = 0%, AE = 9.1%, ST = 100%; SON: control = 10%, CR = 10%, AE = 10%, ST = 50%; NON: control = 7.7%, CR = 0%, AE = 9.1%, ST = 50%). Interestingly, fish from the most southerly latitude, where regulations are the most liberal, abandoned nests at higher rates than did fish from the other latitudes. Collectively, these data reveal that the reproductive success of individual smallmouth bass can suffer from interaction with anglers, particularly in a tournament context, regardless of the region. Further study is needed to determine the extent to which individual nest success is relevant to recruitment and how this relationship varies across latitudes.
The three sampling locations (MO: 36°25′00″N, 92°45′00″W, sampled April 30–May 4, 2007; SON: 44°33′00″N, 76°20′00″W, sampled May 18–19, 2007; and NON: 48°38′00″N, 93°15′00″W, sampled June 11–13, 2007) represented almost the entire latitudinal range of smallmouth bass in North America (Scott and Crossman 1973). The surface area and mean depth were 18,390 ha and 20.4 m at the MO site; 787 ha and 2.5 m at the SON site; and 92,100 ha and 9.8 m at the NON site. Each lake contained a population of resident, naturally reproducing smallmouth bass and was representative of lakes within its particular region with respect to angling for this species. Angling regulations during the study varied between jurisdictions. In MO, there were no restrictions on black bass fishing during the spawning period aside from a 381‐mm minimum length limit and a six‐fish daily creel limit. In addition, competitive angling events occurred throughout the spawning season in MO. In SON, it was illegal to target black bass during the reproductive period; consequently, competitive black bass angling events were prohibited during this period. However, angling pressure for northern pike Esox lucius in the shallows was quite high, and previous work in this system revealed that compliance with regulations designed to protect spawning black bass was low (Philipp et al. 1997). Historically, the closed season was effective from late fall to the last week in June. In NON, there was no closed season but there was a 350‐mm maximum length limit and a two‐fish daily creel limit. However, because of an abundant population of walleyes Sander vitreus , very few anglers target smallmouth bass during the nesting period (D. McLeod, Ontario Ministry of Natural Resources, personal communication).
Smallmouth bass nests with young eggs (<4 d old) were located during daily snorkeling surveys of the littoral zone in each lake. Although the actual spawn timing varied across lakes, water temperatures at the time of spawning and during sampling were similar among the sites (MO = 15.4°C; SON = 14.7°C; NON = 15.0°C). Upon location of a nest, the snorkeler marked the nest with a numbered polyvinyl chloride tile for identification purposes and recorded nest depth, approximate male size, and egg score (a categorical assessment of the number of eggs in a nest; scale of 1–5, where 1 = low and 5 = high; Suski et al. 2003; Hanson et al. 2007). Fish were then randomly assigned to a control group or one of three treatment groups (i.e., CR, air exposure [AE], or simulated tournament [ST]) designed to mimic common angling practices throughout North America. Control fish were not disturbed beyond the initial snorkel survey and a follow‐up assessment (see below). For the CR treatment, each fish was angled from its nest, landed within 30 s (mean ± SE = 18.6 ± 1.8 s), and transferred to a foam‐lined sampling trough filled with fresh, oxygenated lake water for hook removal and blood sampling. After the hook was removed, the fish was held supine so that blood (∼1 mL) could be collected via caudal venipuncture (Houston 1990) using a 3‐mL Vacutainer (lithium heparin anticoagulant; 21‐gauge, 38.1‐mm [1.50‐in] needle; Becton, Dickinson, and Co., Franklin Lakes, New Jersey). The filled Vacutainer was immediately placed in an ice slurry until analysis (described below). The fish was then measured for total length (mm) and released within 10 m of the nest location. In the AE treatment, each fish was angled exhaustively (duration = 78.7 ± 5.6 s) prior to landing. When landed, the fish was exposed to air for 3 min prior to blood sampling, length measurement, and release as described above. For the ST treatment, each fish was angled to exhaustion (duration = 40.9 ± 4.6 s) and landed. Upon landing, the fish was confined (confinement period = 1.7 ± 0.1 h) in a 40‐L live well filled with lake water that was refreshed frequently. Additionally, to avoid water quality degradation due to overcrowding, no more than two individuals were confined in a live well at the same time. At the end of the confinement period, each fish was removed from the live well, exposed to air for 3 min, immersed in the sampling trough, and sampled as described above. The fish was then released into the littoral zone along the same shoreline as the nest, in an area that was 1 km (as determined using a portable Global Positioning System unit) from the nesting site. The release sites were chosen to mimic typical tournament conditions in which fish are released at a central location (and thus the tournament capture sites vary in distance from the release location). Each nest was visited 24 h after treatment to assess the presence or absence of the male (identifiable by a fin clip). Similar studies of simulated angling treatments have indicated that nest abandonment in response to treatment occurs primarily within the first 24 h (Hanson et al. 2007; M. J. Siepker unpublished data). Additionally, the 24‐h interval was chosen to avoid confounding the effects of simulated angling with the effects of brood predation or decreased numbers of hatched embryos, which can result in natural abandonment.