The red king crab fishery: handling effects, bait efficiency, and pot behavior

Thesis (Ph.D.) University of Alaska Fairbanks, 1996Red king crabs (Paralithodes camtschaticus) are caught by pots in a male-only fishery in Alaska. The objectives of this research were: (1) to examine impacts of the commercial fishery on discarded female and sublegal male crabs; (2) to examine bait efficiency; (3) to document crab behavior to pots; and (4) to develop a model describing catch versus soak time. I estimated from observer data that 64.6% of crabs in the Bering Sea fishery were females and sublegal males; I simulated commercial crab handling procedures in the laboratory to test effects on discarded crabs. Although body damage increased significantly with increased handling, there were no significant effects on righting time, feeding rate, weight gain, carapace length increment, or survival. I examined the efficiency of five potential baits (squid, herring, mussel, king crab muscle, and king crab ovary) by observing chemoreception and feeding behavior of the crabs. Chemosensory threshold varied between 10\sp{-4} to 10\sp{-6} g.L\sp{-1}, and feeding threshold ranged from 10\sp{-2} to 10\sp{-3} g.L\sp{-1}. Crabs were most sensitive to the extract of conspecific muscle, while herring was most effective in arousing feeding behavior. Little difference existed between males and females in chemoreception and feeding behavior. Behavioral responses of the crabs to crab pots were observed by time-lapse video. Crabs approached the pot from downstream, and 78.3% of crabs searched less than 90\sp\circ before leaving or entering the pot. The entry success rate was 8.1%. Only large males could begin escape from the bottom panel. Crabs had difficulties in accessing the pot and in escaping from inside the pot. The standard pot appeared inefficient in catching legal males, while it retained many non-legal crabs. I constructed a general model to describe the relationship between catch and soak time for trap fisheries. The model is expressed as C\sb{t}=ab+a(t-b)\ e\sp{-ct}, where C\sb{t} is the catch per trap haul at soak time t, and a, b, and c are parameters to be estimated. This model is suitable for both short and long soak times

Multi-asset Spread Option Pricing and Hedging

We provide two new closed-form approximation methods for pricing spread options on a basket of risky assets: the extended Kirk approximation and the second-order boundary approximation. Numerical analysis shows that while the latter method is more accurate than the former, both methods are extremely fast and accurate. Approximations for important Greeks are also derived in closed form. Our approximation methods enable the accurate pricing of a bulk volume of spread options on a large number of assets in real time, which offers traders a potential edge in a dynamic market environment.multi-asset spread option, closed-form approximation

A maximum likelihood estimate of natural mortality for brown tiger prawn (Penaeus esculentus) in Moreton Bay (Australia)

The delay difference model was implemented to fit 21 years of brown tiger prawn (Penaeus esculentus) catch in Moreton Bay by maximum likelihood to assess the status of this stock. Monte Carlo simulations testing of the stock assessment software coded in C++ showed that the model could estimate simultaneously natural mortality in addition to catchability, recruitment and initial biomasses. Applied to logbooks data collected from 1990 to 2010, this implementation of the delay difference provided for the first time an estimate of natural mortality for brown tiger prawn in Moreton Bay, equal to $0.031 \pm 0.002$ week$^{-1}$. This estimate is approximately 30\% lower than the value of natural mortality (0.045 week$^{-1}$) used in previous stock assessments of this species

(R)-(−)-N-Isovalerylcamphorsultam

The title compound, C15H25NO3S, was prepared from (R)-(−)camphorsultam and isovaleryl chloride. The asymetric unit contains two independent mol­ecules with slightly different conformations. In the crystal, weak inter­molecular C—H⋯O hydrogen bonds link mol­ecules into two independent hydrogen-bonded chains propagating along the a and b axes

Nonlinear dynamic characteristic of gear system with the eccentricity

In this paper, the dynamic behavior of a spur gear system was studied with external and internal dynamic incentive. The vibration differential equations for spur gear system were expressed in equivalent discrete models of mass, damping, and spring elements using the Lagrange equation considering the effect of lateral-torsional vibration coupling on the dynamics of gears, which was solved by the Newmark method. The investigation was carried out with multi-degree of freedom system for spur gear model, which took into account gravity, gear eccentricity, backlash, dynamic transmission error and external dynamic incentive. The lateral and torsional response characteristics of geared system were analyzed by changing the value of the rotational speed, backlash and eccentricity. It was shown from the research that the jump discontinuous phenomenon occurred at lower backlash value with increasing rotational speed and the frequency amplitudes also increased, and the regions of continuous frequency became winder when the rotational speed difference was greater. Moreover, complicated combination frequency components followed a rule of increasing firstly and then decreasing with the different backlash and eccentricity. The study may contribute to a further understanding of the dynamic characteristics of such a gear rotor-bearing system

The Dichotomy Property in Stabilizability of 2×22\times2 Linear Hyperbolic Systems

This paper is devoted to discuss the stabilizability of a class of $2 \times2$ non-homogeneous hyperbolic systems. Motivated by the example in \cite[Page 197]{CB2016}, we analyze the influence of the interval length $L$ on stabilizability of the system. By spectral analysis, we prove that either the system is stabilizable for all $L>0$ or it possesses the dichotomy property: there exists a critical length $L_c>0$ such that the system is stabilizable for $L\in (0,L_c)$ but unstabilizable for $L\in [L_c,+\infty)$. In addition, for $L\in [L_c,+\infty)$, we obtain that the system can reach equilibrium state in finite time by backstepping control combined with observer. Finally, we also provide some numerical simulations to confirm our developed analytical criteria