Estimating Salmonid Food Webs in Large River Ecosystems

Estimating prey availability within large river ecosystems presents numerous challenges for wildlife managers and freshwater ecologists. Conventional methods, which utilize drift-nets, becomes difficult with increasing water velocity due to the accumulation of organic material within nets of a certain mesh size (Hauer and Lambert 2007). In addition, the processing of multiple drift-net samples can prove to be time consuming and expensive. Together these constraints significantly limit the capacity to sample large rivers at the necessary temporal and spatial scales.  The development and fine tuning of next generation camera technology and high resolution photo imagery could prove to be a valuable alternative when sampling insect dispersal in various capacities of lotic environments. The Scripps Plankton Camera (SPC), employs a Point Grey Grasshopper 3 – 12 mega-pixel camera with high intensity LED strobes, Opto-Engineering 0.137X magnification lens and Odroid-XU4 electronics to detect semi-transparent organisms in turbid environments. The camera is governed by a C++ program and runs in a standard LINUX operating system. Prototypes of the SPC have been deployed to continuously and effectively measure meiofauna in oceanic environments. However the application of the SPC in riverine ecosystems has yet to be explored.

Riparian-Stream Linkages in Upland Redwood Forests

Within the range of California coastal redwood, historic logging practices, reduced fog frequency, and increased drought stress have been shown to influence the composition and physiology of upland redwood stands. Upland redwood stands are dominated by coast redwood (Sequoia sempervirens), Douglas-fir (Pseudotsuga menziesii), and tanoak (Notholithocarpus densiflorus) which exhibit slow decomposition rates, a high C:N ratio, large amounts of secondary plant compounds, and exhibit heavy canopy structure that limits primary production within freshwater stream ecosystems. Inputs from terrestrial vegetation (allochthonous) are a major source of energy for forested headwater communities where low light levels can greatly limit instream photosynthesis (autochthonous). Composition of terrestrial inputs can be attributed to local habitat structure, precipitation, tree species, and will directly influence the secondary production of aquatic organisms, as well as the rate of allochthonous carbon processing. In the wake of increased drought stress and anthropogenic impacts, the prevailing juxtaposition within upland redwood stands could influence invertebrate prey biomass and have cascading effects to higher levels of the trophic network, particularly drift-feeding fish downstream. Physical characteristics paired with timing, composition, and quality of detrital inputs, as well as limited primary productivity are all important drivers of invertebrate biomass within coastal redwood streams.

Population Genetics of the Red Claw Crayfish Recently Introduced to the Island of Puerto Rico

Crayfish introductions have been widely recognized as a threat to native diversity and ecosystem function.  Introduction events involve a few founding individuals which could limit genetic diversity and establishment potential. Diversity within introduced populations will decrease due to bottlenecks and drift, or increase as a result of multiple introduction events. I present here a case study which documents the current population dynamics and genetic variation of Cherax quadricarinatus (Red Claw) recently introduced to the island of Puerto Rico. Red Claw were sampled from six reservoirs (Loiza, Cidra, Carite, Güajataca, El Guineo, Dos Bocas) throughout the island, as well as an aquaculture facility (Caribe Fisheries) located in the Southwest. Relative abundance was estimated using a Catch-Per-Unit-Effort approach (the number of individuals per trapnight ~24hrs) with Cidra having the highest (2.20). A length-mass relationship developed a power equation where Biomass (M) is predicted by taking Standard Carapace Length (SCL) to the power b= 3.4451 and multiplying by a = 0.0057 (M = (0.0057) SCL (3.4451)). ANOVA suggested differences in overall SCL (F(4,134)= 16.96, P< 0.0001) and Biomass (F(4,145)=15.59, P<0.0001) among sample sites with Loiza being significantly different in both cases. Seven microsatellite loci were used to assess genetic variation between populations. Allelic diversity was observed to be highest in Caribe and lowest in Cidra. AMOVA supported significant variation within total individuals (50%; p<0.001). Pairwise Fst was lowest between Cidra and Guajataca (Fst = 0.007), and the number of migrants per generation (Nm) was highest between these two populations (Nm = 36.167). Permutated Mantel tests indicated that isolation-by-distance has had little influence on genetic variation (r= 0.038, p = 0.384). STRUCTURE results supported a K = 2 as being the most probable number of populations. This study supports previous surveys indicating that Red Claw is established in Puerto Rico. My work is the first to present island wide distribution and relative abundance estimates for areas not previously surveyed. Genetic analysis supports strong structuring between populations as the result of small founder events. Biomass estimates will allow for a standardized measure to assess the role of Red Claw in ecosystem processes.  Overall, results will contribute to the concern of Red Claw introduction outside of its native range.