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We used creel survey data collected from 1975 to 2006 to evaluate temporal changes in the voluntary release of legally harvestable largemouth bass Micropterus salmoides at four Texas reservoirs and two Florida lakes noted for providing high-quality largemouth bass fisheries. The voluntary release rate increased substantially over time at all six water bodies and reached asymptotic levels exceeding 0.90 in two Texas reservoirs in the early 2000s. Year explained from 68% to 96% of the variability in voluntary release rates. The level of voluntary release ranged from 0.53 to 0.99 among Texas reservoirs in the early 2000s. The increase in voluntary release over time was similar at the two Florida lakes, which had identical largemouth bass harvest regulations, but the levels differed. Catch and release of legally harvestable largemouth bass was more prevalent than harvest at five of the six water bodies included in this study but also varied across small spatial scales. Fishery managers should measure the level of voluntary release and be mindful of the potential effects of high voluntary release when considering the use of harvest restrictions to restructure largemouth bass populations. [ABSTRACT FROM AUTHOR]

We reviewed estimates of annual exploitation (u) and total mortality (Z) for populations of largemouth bass Micropterus salmoides and used a simulation model to explore how temporal changes in u have influenced those populations. The review produced 32 estimates of u and 30 of Z spanning 51 years. Fishing mortality was roughly parabolic through time, with a mean of 0.35 for 1976-1989 and a mean of 0.18 for 1990-2003. Thus, average fishing mortality rates have declined by about one-half since about 1990. Total mortality declined with the decline in u, suggesting that changes in u caused lower overall total mortality rates. The evidence further suggests that the decline in u was caused by the voluntary release of fish by anglers rather than by changes in overall fishing effort. The simulation model showed that the decline in exploitation increased adult largemouth bass abundance but reduced the ability of size and bag regulations to improve population metrics owing to low rates of directed harvest. Discard mortality (i.e., the mortality of fish caught and released) would not negate the benefits of lower exploitation unless the mortality of fish caught and released was 0.3 or higher. Changes in angler behavior have substantially reduced fishing mortality for largemouth bass fisheries, which should be considered when developing management plans for this species and others with high rates of voluntary release. [ABSTRACT FROM AUTHOR]

Abundance of the spotted sunfish has been positively correlated with interannual fluctuations in river stage, making this a potential indicator species for streamflow management. We evaluated patterns of habitat selection by adult and juvenile spotted sunfish and related them to simulated declines in river stage at three southwestern Florida rivers (Anclote, Little Manatee, and Manatee rivers). To identify habitat selection patterns, we used multivariate analysis of variance to compare measured characteristics (i.e., current velocity, depth, and cover abundance) of habitats used by spotted sunfish with those of randomly located habitats within the stream margin environment. Spotted sunfish generally selected habitats with greater structural complexity than the average available habitat. In many instances, spotted sunfish appeared to select habitats that contained both large and fine woody debris. However, fish were collected from a variety of habitat types during the study, indicating that this species is somewhat general in its habitat use. We found few significant differences in habitat measures between juvenile and adults, suggesting that habitat selection was similar between these life stages. Our model simulations indicated that 0.3-m reductions in average daily river stage could reduce habitat availability for spotted sunfish by 20-70% across systems. Spotted sunfish used habitats with greater-than-average resiliency to stage declines (i.e., deeper, more complex habitat). Considering that even minor reductions in the average daily stage during fall and spring could substantially reduce overall availability of suitable habitat, the inundation of complex habitat types is probably important for spotted sunfish. [ABSTRACT FROM AUTHOR]

American shad , hickory shad , and blueback herring spawn in Florida's St. Johns River during winter and spring, and juveniles migrate out of the estuary during the following fall. We assessed the temporal trends of juvenile relative abundance and size as each species moved downstream past Palatka, Florida, and compared these values to historical data from the system. Juveniles were collected from April 2004 to March 2005 primarily with surface trawling at night and with supplemental daytime electrofishing. Relatively few juveniles were collected by trawl (23 American shad, 7 hickory shad, and 36 blueback herring) or by electrofishing (55 American shad, 4 hickory shad, and 179 blueback herring). Trawl catch rates were highest in autumn, and electrofishing catch rates were highest in autumn and early winter. Both sampling methods caught juveniles at similar sizes. The surface trawl catch rates of juvenile American shad in 2004 and 2005 were not significantly different from comparable historical catch rates for 1969 and 1970, suggesting similar overall juvenile recruitment levels. Trawl collections were sufficient to document the seasonal downstream migration of shad juveniles. However, given the low catch rates, we found electrofishing to be a useful alternative method for describing seasonal abundance and habitat use by juvenile shad. [ABSTRACT FROM AUTHOR]

We evaluated the effects of variable flows on water chemistry and fish communities to recommend biologically based minimum flows that protect low-salinity zones for freshwater-oligohaline (FO) fishes below the Hillsborough River Dam, Tampa, Florida. We plotted the distributions of hypoxic (dissolved oxygen [DO] ≤ 4 mg/L) and meso- and polyhaline (salinity > 5‰) habitats and evaluated changes in species richness and spatial distributions of FO fishes on five sampling dates from October 2002 to July 2004. During low flows (0.12 m³/s; <25th percentile) in May 2004, oligohaline habitat was reduced as a salt wedge (>5‰) migrated upstream to within 1,300 m of the dam and DO decreased to less than 4 mg/L in the lower part of the reach. However, intermediate (1.19-2.18 m³/s; 25th-50th percentiles) and high flows (5.49 m³/s; 50th-75th percentiles) on four of the five sampling dates maintained oligohaline salinities (i.e., ≤5‰) and DO greater than 4 mg/L throughout most of the reach. Using fyke net data, we found no flow-related trends in FO fish species richness. However, spatial occurrence data indicated that the distribution of FO fishes shifted upstream to within 1,660 m of the dam during a low flow in May 2004. Thus, FO fishes may have congregated in the upper part of the reach or moved out of the lower reach because of unsuitable water quality during low flows. Our results suggest that the best minimum flow to preserve obligate freshwater and oligohaline fishes in the lower Hillsborough River would be between 0.12 m³/s, which eliminated freshwater and reduced oligohaline habitat, and 1.19 m³/s, which provided freshwater and oligohaline habitat throughout most of the study reach. Freshwater flows below the Hillsborough Dam influenced salinity gradients and the spatial occurrence of FO fishes in this system. Low-salinity habitats and FO fish taxa should be considered when setting minimum flows for estuaries. [ABSTRACT FROM AUTHOR]

In an effort to aid in the conservation of black basses, the relative abundance, growth, and mortality of Suwannee bass Micropterus notius and largemouth bass M. salmoides were estimated from four Florida rivers. Fish were collected by electrofishing in the four rivers during 2001 and 2002. Electrofishing catch per unit effort of Suwannee bass was highest in the Wacissa River (95.1 fish/h), intermediate in the Santa Fe River (22.6 fish/h), and lowest in the Withlacoochee (5 fish/h) and Ochlockonee rivers (1.9 fish/h). Catch per unit effort for largemouth bass was also highest in the Wacissa River (50 fish/h), intermediate in the Santa Fe (19.8 fish/h) and Ochlockonee rivers (17.1 fish/h), and lowest in the Withlacoochee River (9.9 fish/h). Mean total length (TL) at age across the four Suwannee bass populations was described by von Bertalanffy growth curves as TL = 386.1 ⋅ (1 - e-0.3733[age+0.7772]) for females and as TL = 324.1 ⋅ (1 - e-0.4735[age+0.6543]) for males. Mean TL at age across the three largemouth bass populations was also described by von Bertalanffy growth curves as TL = 644.2 ⋅ (1 - e-0.2064[age+0.9840]) for females and TL = 427.8 ⋅ (1 - e-0.3164[age+0.9991]) for males. Suwannee bass exhibited sex-specific growth rates similar to those of largemouth bass, females experiencing more rapid growth and attaining larger sizes than males (F1, 564 = 20.39; P < 0.01). Suwannee bass total annual mortality (A) averaged 40%, ranging from 28% to 46%. Similarly, largemouth bass total A averaged 40%, ranging from 35% to 46%. The current Florida minimum length limit on Suwannee bass directs fishing mortality almost solely to females, but estimates of fishing mortality are needed to determine whether this is a concern for black bass with a small native range. [ABSTRACT FROM AUTHOR]

Crappies spp. are popular sport fishes but are often difficult to manage due to highly variable recruitment. To assess the factors influencing recruitment, we investigated the size and abundance of age-0 black crappie in relation to zooplankton density, adult stock abundance, and water clarity in three productive Florida lakes. Age-0 black crappies were collected at Lakes Wauberg, Lochloosa, and Tarpon by use of surface and bottom trawls during the spring, summer, and fall of 2000 and 2001. Zooplankton abundance was measured concurrently with trawl sampling. Early-summer juvenile abundance was positively related to stock abundance during the previous fall among lakes, indicating a relationship between stock size and juvenile black crappie abundance. Early-summer juvenile abundance was positively related to juvenile abundance in the fall (i.e., at the end of the first summer), suggesting that year-class strength was set by early summer in all lakes. Lake Lochloosa had the highest crustacean zooplankton abundance in both years, but this lake had the smallest age-0 black crappie size and intermediate age-0 fish abundance. Thus, we found no relationship between crustacean zooplankton density and black crappie size across lakes. Reduced Secchi depths due to high chlorophyll- a values and wind resuspension of sediments may have reduced feeding efficiency for age-0 black crappies at Lake Lochloosa relative to the other lakes. Age-0 black crappie abundance and size during fall were not predicted solely by food availability, stock abundance, or water clarity, suggesting that these factors interacted to influence recruitment through the first year of life. [ABSTRACT FROM AUTHOR]

Black crappies Pomoxis nigromaculatus exhibit highly variable survival to adulthood because of their varying larval and juvenile abundance, growth, and mortality during early life. We examined how growth and mortality changed with hatch date, prey density, and water temperature for 7-d cohorts of juvenile black crappies in Lake Wauberg, Florida (a 150-ha hypereutrophic natural lake) during spring and summer 1998. Fish were collected once per week from March through June and twice per month during July and August by means of an otter trawl. Based on daily otolith rings, hatching occurred over a 12-week period (1 March−18 May). The mean daily growth rate (DGR) was positively related to water temperature, which increased over the hatching season. Common prey taxa included calanoid copepods, Daphnia and Bosmina spp., and cyclopoid copepods. The total density of these taxa did not differ significantly among collection dates. Mean hatching date shifted from mid-March for fish collected in mid-April to early April for fish collected in late May. Early-hatched fish had lower DGRs (0.72 mm/d, compared with 0.76 mm/d for fish hatched in midseason and 0.82 mm/d for those hatched late in the season), higher mean daily instantaneous mortality rates (0.25, compared with 0.09 for the other two groups), and lower survival to the end of the first summer. As a result, the 1998 year-class of black crappies in Lake Wauberg was probably dominated by middle- and late-hatched individuals by the end of the first summer. [ABSTRACT FROM AUTHOR]

Factors that affect recruitment of threadfin shad Dorosoma petenense and gizzard shad D. cepedianum, two important prey species in southern reservoirs, are not well understood. Larval shad typically have not been identified to species, though interactions between shad larvae likely affect their recruitment and that of their predators. Using myomere counts to identify larval shad to species, we quantified spatial and temporal variation in species distributions in West Point Reservoir, Alabama-Georgia. We sampled larvae every 3-4 d at three distances from shore (inshore and 25 and 50 m offshore) at each of three sites. Larval threadfin shad migrated offshore in all three sites, whereas larval gizzard shad were evenly distributed across distances from shore. Because of these movement differences, larval gizzard shad and larval threadfin shad may encounter different habitat-specific predation rates, climatic effects, and food availability. In addition, larval gizzard shad were present before larval threadfin shad and grew beyond the size vulnerable to our capture techniques before threadfin shad abundance peaked. If zooplankton densities are reduced by young-of-year shad, as documented in other systems, later-hatched threadfin shad would encounter fewer zooplankton than were available to the earlier larval gizzard shad. Threadfin shad would have reduced growth and greater vulnerability to predation and starvation. [ABSTRACT FROM AUTHOR]

In the Western Indian Ocean (WIO) region, information and data on marine recreational fisheries (MRF) is lacking, which undermines efforts towards their sustainable development. Our paper reviews the challenges and opportunities for sustainably developing marine recreational fisheries in the WIO. We identified several challenges that are discussed in two broad categories: (i) governance and (ii) socio-cultural and economic. We also show that addressing these challenges requires a holistic understanding of the socio-ecological complexities and the multi-scale nature of WIO MRF. Realizing the potential for sustainable development of this sector calls for the involvement of coastal communities in the sharing of benefits and decision-making. Further, coordinated efforts between the multi-government agencies and non-governmental organizations is critical for integrating recreational fisheries into local and national agendas. We conclude that the sustainable development of MRF in the WIO region is possible. Still, such growth will be dependent upon the sustained capacity building of coastal communities and indigenous fishers, collaboration from stakeholders, and the long-term sustainability of the resource. • Challenges for sustainable Marine Recreational Fisheries (MRF) in the Western Indian Ocean (MRF) are complex and diverse. • Challenges are associated with governance, socio-cultural and economic factors which hinder the potential of MRF. • Limited capacity, fisheries conflicts, and inadequate participation of local and indigenous communities undermine the development of MRF. • Urgent need for an integrated approach that incorporates all stakeholders for the sustainability of the resource. [ABSTRACT FROM AUTHOR]